Aerosol generator with improved aerosol extraction

Abstract

The aerosol generating system (400) comprises a heater assembly (100), which includes a heating element (104) and a porous body (102), the porous body having a liquid absorption surface (102b) and a heating surface (102a), the heating element being positioned on the heating surface of the porous body, the heating element being fluid permeable, so that when in use, vapor is released from the heater assembly in the mean vapor release direction, the aerosol generating system further includes an air intake and an aerosol outlet, thereby defining an airflow path through the aerosol generating system, the heater assembly being arranged in fluid communication with the airflow path so that air flows through the heater assembly in the mean airflow direction, and the heater assembly and the airflow path being arranged such that the angle between the mean vapor release direction and the mean airflow direction is less than 90 degrees.

Description

[Technical Field]

[0001] This disclosure relates to an aerosol generating system. In particular, but is not exclusive, this disclosure relates to a handheld, electrically operated aerosol generating system for heating an aerosol-forming substrate to generate an aerosol and delivering the aerosol to a user's mouth. [Background technology]

[0002] Aerosol generating systems that heat a liquid aerosol-forming substrate to generate an aerosol to be delivered to a user are generally known in the prior art. These aerosol generating systems typically include a part for holding the liquid aerosol-forming substrate and a heater assembly for heating the liquid aerosol-forming substrate. In one type of known aerosol generating system, the heater assembly comprises a resistance heating element wound around a wick that supplies the liquid aerosol-forming substrate to a heating element. In another type of known aerosol generating system, the heater assembly comprises a solid porous body having a heating element arranged on one surface. The porous body transports the liquid aerosol-forming substrate to the heating element. When a user inhales smoke over the aerosol generating system, air is drawn in through the aerosol generating system, and an electric current flows through the heating element, which is heated by resistance heating or Joule heating. The heating element heats the liquid aerosol-forming substrate supplied by the wick or porous body, thereby releasing volatile compounds from the liquid aerosol-forming substrate, which, upon cooling, form an aerosol. The aerosol is then drawn into the user's mouth through the mouthpiece of the aerosol generating system.

[0003] A known problem encountered in aerosol generating systems is that the aerosols generated by the heater are not properly drawn into the airflow passing through the system. As a result, the aerosols can condense on the inner surface of the aerosol generating system. If a sufficient amount of aerosol condenses on the inner surface of the aerosol generating system, large droplets of liquid aerosol-forming substrate may form and flow into the user's mouth. This can result in an unpleasant and undesirable user experience. Furthermore, condensation within the aerosol generating system can damage the system, for example, by corroding surfaces or damaging circuits.

[0004] The inventors have found that condensation in an aerosol generation system can occur due to several factors. One factor is the placement of the heater assembly in relation to the airflow path. Figure 1 shows a schematic cross-sectional view of a known type of heater assembly 1 placed in an airflow path. The heater assembly 1 comprises a solid porous body 2 and a heating element 4. The heating element 4 is formed as a continuous track on the lower surface of the solid porous body 2, and several track portions 4a of the heating element 4 are visible in the cross-sectional view of Figure 1. The heater assembly 1 is designed to be placed in an opening at the base of a storage section, i.e., a liquid storage section (not shown), for holding a liquid aerosol forming substrate. The upper surface of the heater assembly 1 receives the liquid aerosol forming substrate from the liquid storage section, and the liquid aerosol forming substrate is transported through the solid porous body 2 to the heating element 4, as indicated by arrow A in Figure 1.

[0005] The liquid aerosol-forming substrate is vaporized by the heat from the heating element 4, and the vapor is released from the lower surface of the solid porous body 2 between the heating element track portions 4a, as shown by arrow B in Figure 1. The heater assembly 1 is positioned so that its lower surface faces the opposing airflow path shown by arrow C in Figure 1. The airflow path C flows from the air intake (not shown) toward the lower surface of the heater assembly 1, so that the airflow direction is opposite to the vapor release direction B from the lower surface of the heater assembly 1. The vapor released from the heater assembly is drawn into the airflow path C and cooled, forming an aerosol. Subsequently, the air containing the aerosol follows the airflow path C, passing around the heater assembly 1, and continues to the aerosol outlet (not shown) where the aerosol is supplied to the user's mouth.

[0006] In order to entrain the steam into the airflow, the direction of the steam needs to be changed from the steam discharge direction B to the direction of the airflow path C. The change in steam direction is indicated by arrow D in Figure 1. As can be seen from Figure 1, in order to entrain the steam into the airflow path C, the airflow needs to almost completely reverse the direction of steam discharge so that the steam flows in the opposite direction with the airflow. Because the steam and airflow are moving in opposite directions, the momentum of the steam and airflow is significantly lost, which can cause recirculation or turbulence in the airflow path C. As a result, the aerosol is not properly entrained into the airflow and is not properly extracted from the device. Furthermore, as the aerosol and airflow lose momentum and generate turbulence, the steam collides with the inner surface (not shown) that defines the airflow path C, forming condensates, which can accumulate and form droplets of liquid aerosol-forming substrate. This problem can be overcome to some extent by increasing the airflow velocity. However, increasing the airflow velocity can adversely affect the heater assembly in order to cool the heating element, and it also prolongs the time it takes for the liquid aerosol-forming substrate to reach its boiling point, thereby reducing the aerosolization performance.

[0007] Another factor that causes condensation within an aerosol generating system is the vapor ejection velocity. In heater assembly 1 of Figure 1, thermal energy is supplied by the heating element 4, and vapor ejection is generated when the liquid aerosol-forming substrate vaporizes within the solid porous body 2. The thermal energy, or heat, raises the temperature of the heating track 4a, the solid porous body 2, and the liquid aerosol-forming substrate contained within the porous body 2. When the liquid aerosol-forming substrate reaches its boiling point, it vaporizes. The heating element track 4a of known heater assemblies is typically formed from a resistant metal element that is impermeable to fluids. Therefore, vapor cannot escape from the solid porous body 2 in the region directly below the heating element track 4a, and the vapor pressure increases in those regions of the porous body 2. The vapor cannot pass through the heating track 4a and must bypass it. Therefore, the vapor is ejected from both sides of the heating track, as illustrated by arrow B in Figure 1. The inventors have found that the vapor ejection generated by known heater assemblies can be relatively fast when a standard amount of operating power is supplied to the heater assembly. For example, when 6.3 watts of power was supplied to the heater assembly, a vapor ejection velocity of 0.5 meters / second was measured. It was found that such a velocity is sufficient for the vapor to collide with the inner wall of the airflow path C inside the aerosol generation system and form condensates.

[0008] It is desirable to provide an aerosol generation system that reduces aerosol condensation within the system. Furthermore, to improve aerosol extraction, it is desirable to provide an aerosol generation system that increases the entrainment of aerosols into the airflow passing through the system. [Overview of the project]

[0009] An example of this disclosure provides an aerosol generating system. The aerosol generating system may include a heater assembly. The heater assembly may include a heating element. The heating element may be configured to vaporize a liquid aerosol forming substrate. The heater assembly may include a porous body. The porous body may be configured to transport the liquid aerosol forming substrate to the heating element. The porous body may have a liquid absorption surface. The porous body may have a heating surface. The heating element may be placed on the heating surface of the porous body. The heating element may be fluid permeable. During use, vapor may be released from the heater assembly in the mean vapor discharge direction. The aerosol generating system may include an air intake. The aerosol generating system may include an aerosol outlet. The air intake may be in fluid communication with the aerosol outlet. An airflow path may be defined through the aerosol generating system. The heater assembly may be arranged in fluid communication with the airflow path. During use, air may flow through the heater assembly in the mean airflow direction. The heater assembly and the airflow path may be arranged such that the angle between the average steam discharge direction and the average airflow direction is less than 135 degrees. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view of a known type of heater assembly 1 installed in an airflow path. [Figure 2] This is a schematic plan view of a heater assembly according to an example of the disclosure. [Figure 3] Figure 2 is a schematic cross-sectional view of the heater assembly. [Figure 4] This is a schematic diagram of the internal structure of an aerosol generation system according to an example of the disclosure. [Figure 5] A schematic cross-sectional view of a part of an aerosol generating system according to another example of the present disclosure, showing the arrangement of a heater assembly with respect to the airflow path inside the aerosol generating system. [Figure 6]Schematic cross-sectional view of a part of another aerosol generation system according to another example of the present disclosure, showing the arrangement of the heater assembly with respect to the airflow path inside the aerosol generation system. [Figure 7] Schematic perspective view of a heater assembly according to another example of the present disclosure. [Figure 8] Schematic side view of the heater assembly of FIG. 7. [Figure 9] Schematic plan view of a heater assembly according to another example of the present disclosure. [Figure 10] Schematic perspective view of a heater assembly according to another example of the present disclosure. [Figure 11] Schematic cross-sectional view through a heater assembly according to another example of the present disclosure. [Figure 12] Schematic cross-sectional view through a heater assembly according to another example of the present disclosure. [Figure 13a] Schematic view of three heating elements for an aerosol generation system. [Figure 13b] Schematic view of three heating elements for an aerosol generation system. [Figure 13c] Schematic view of three heating elements for an aerosol generation system. [Figure 14a] Schematic view showing the current around the corner of the heating element track. [Figure 14b] Schematic view showing the current around the corner of the heating element track.

Mode for Carrying Out the Invention

[0011] Here, various examples will be further described while referring to the drawings.

[0012] It will be understood that at least some of the drawings in the present application are schematic and are simplified for the purpose of clarity. As a result, some features may be omitted and not all features are necessarily shown to scale.

[0013] References to orientation, such as vertical, horizontal, up, down, upper side, and lower side, when describing the features of this disclosure are not intended to limit the orientation of those features, but are simply intended to show the relative spatial arrangement of the features, particularly with reference to the figures or in normal use. It will be understood that the features of this disclosure may have different orientations when used.

[0014] Referring to Figure 2, a heater assembly 100 is shown, which comprises a heating element 104 for vaporizing a liquid aerosol-forming substrate and a porous body 102 for supplying the liquid aerosol-forming substrate from a storage section, i.e., a liquid storage section (not shown), to the heating element 104. The porous body 102 has a liquid absorption surface (not shown) and a heating surface 102a. The heating element 104 is disposed on the heating surface 102a of the porous body 102.

[0015] The heating element 104 is formed from a layer of conductive material, allowing it to be heated by resistance heating or Joule heating by passing an electric current through it. The heating element 104 is also porous, and therefore fluid permeable, allowing vapor to pass through the heating surface 102a of the porous body 102 to the heating element 104. Thus, in the heater assembly 100 of Figure 2, vapor release occurs through the heating element 104. The heating element 104 may comprise a thin metal layer or thin metal film, having pores that extend through the thickness of the layer or film. Alternatively, the heating element may comprise a metal foam, having interconnected open pores that extend through the thickness of the foam. In this example, the porous body 102 comprises a porous ceramic body formed from a suitable ceramic material such as Al2O3. Furthermore, the heating element 104 is deposited on the porous ceramic body 102 using a suitable physical or chemical vapor deposition process.

[0016] The heater assembly 100 further comprises electrical contacts 106 electrically connected to the heating element 12. The electrical contacts 106 are arranged on the heating surface 102a at or near both ends of the heating surface 102a. The heating element 104 extends between the electrical contacts 106. The electrical contacts 106 are arranged to be connected to a control circuit for controlling the power supply to the heating element. The electrical contacts 106 are formed from a material with higher conductivity than the heating element, such as copper, gold, or zinc, but other suitable materials may be used. This avoids the generation of excessive waste heat within the electrical contacts.

[0017] Figure 3 shows a schematic cross-sectional view of the heater assembly 100 shown in Figure 2. For clarity and simplification, the electrical contacts 106 in Figure 1 are omitted in Figure 2, and each feature is not shown to scale. The liquid absorption surface 102b is shown as the lower surface of the porous body 102 in Figure 3, and the heating surface 102a is shown as the lower surface of the porous body 102. However, it should be understood that the orientation of these surfaces may differ during use, and may also differ after the heater assembly 100 is installed in the aerosol generator. The liquid stored in the liquid storage section, i.e., the liquid storage part (not shown), comes into contact with the liquid absorption surface 102b and is transported through the porous body 102 to the heating surface 102a, as indicated by arrow E in Figure 3. The porous heating element 104 is disposed on the heating surface 102a of the porous body 102, and by heating the liquid aerosol forming substrate that has been transported to the heating surface 102a, it boils the liquid aerosol forming substrate and generates steam. The porous heating element 104 has a plurality of pores 108 that penetrate the thickness of the heating element from the heating surface 102a to the outside of the heater assembly 100.

[0018] Because the heating element 104 is porous, the steam generated when the heating element 104 is heated can pass through the heating element 104 via the pores 108, as shown by arrow F in Figure 3, and be released from the heated surface 102a. The heating element has no impermeable parts whatsoever, so the release of steam is not obstructed, and no steam pressure accumulates directly beneath the heating element. As a result, the steam release rate from the heating element 104 is reduced compared to conventional impermeable track heating elements. Table 1 below shows the average steam release rate of steam released from heating elements with various different configurations. The heated area of ​​all heating elements in Table 1 was approximately 5 mm × 3 mm.

[0019] As can be seen from Table 1 below, relatively low vapor release velocities were obtained for all heating elements, i.e., vapor release velocities of less than 1 meter / second. Such low vapor release velocities mean that the vapor can be easily carried away by the airflow within the airflow path, which means that the vapor does not collide with the inner walls of the airflow path and cause condensation. As indicated by arrow F, the average vapor release direction is substantially perpendicular to the heating surface 102a of the porous body 102, and the vapor is released across the entire surface of the heating element.

[0020] [Table 1]

[0021] Figure 4 is a schematic diagram of the interior of an aerosol generating system 200 according to an example of the present disclosure. The aerosol generating system comprises two main components: a cartridge 202 and a main body portion, i.e., an aerosol generator 204. The connection terminal 202a of the cartridge 202 is detachably connected to the corresponding connection terminal 204a of the aerosol generator 204. Each of the connection terminals 202a of the cartridge 202 and 204a of the aerosol generator 204 has electrical contacts, i.e., connectors (not shown), arranged to cooperate to provide an electrical connection between the cartridge 202 and the aerosol generator 204. The aerosol generator 204 comprises a device housing 209, which houses a power source in the form of a battery 206, in this example being a rechargeable lithium-ion battery, and a control circuit 208. The aerosol generating system 200 is portable and has a size comparable to a conventional cigar or cigarette. The mouthpiece 210 is positioned at the oral end 202b of the cartridge 202. The oral end 202b is located on the opposite side from the connection end 202a of the cartridge 202.

[0022] Cartridge 202 is equipped with a cartridge housing 212, which houses a heater assembly 100 and a liquid storage section, or liquid storage portion 218, for holding a liquid aerosol forming substrate. The heater assembly 100 in Figure 4 has a similar structure to those in Figures 2 and 3, but is inverted compared to the orientation in Figures 2 and 3, so that the liquid absorption surface 102b is facing upward and in fluid communication with the liquid storage portion 218, and the heating surface 102a, to which a heating element (not shown) is attached, is facing downward. The liquid aerosol forming substrate is transported downward from the liquid absorption surface 102b through the porous body 102 to the heating element, and the vaporized aerosol forming substrate is released from the heating surface 102a when power is supplied to the heating element. As indicated by arrow F in Figure 1, the average vapor release direction is substantially perpendicular to the heating surface 102a of the porous body 102.

[0023] The cartridge 202 is provided with one or more air intake ports 222 formed in the cartridge housing 212 at positions along the length of the cartridge 202 corresponding to the position of the heating surface 102a of the heater assembly 100. The aerosol outlet 226 is located in the mouthpiece 210 at the mouth end 202b of the cartridge 202. The one or more air intake ports 222, by fluid communication with the aerosol outlet 226, define the airflow path 220 through the cartridge 202 of the aerosol generating system 200. The airflow path 220 flows through the airflow channel 223 from the one or more air intake ports 222 to the heater assembly 100. The heater assembly 100 is disposed within the airflow channel 223, in fluid communication with the airflow channel 220. Air flows in through one or more air intakes 222, as indicated by arrow I in Figure 4, and flows through the airflow channel 223, passing over the heater assembly 100 in the mean airflow direction. As can be seen from Figure 4, the heater assembly 100 and the airflow path 220 within the airflow channel 223 are arranged such that the angle between the mean vapor discharge direction F and the mean airflow direction I is approximately 90 degrees, that is, substantially perpendicular to the mean airflow direction I. Since the mean vapor discharge direction F has no velocity, or directional component, opposite to the mean airflow direction I, the momentum loss of the vapor is reduced. As a result, the tendency for vapor recirculation and turbulence to occur within the airflow path 220 is reduced, and the vapor is less likely to collide with the inner surface of the airflow channel 223.

[0024] In the example shown in Figure 4, the liquid storage section 218 has an annular cross-section and is arranged around a central sealed aerosol channel 224. When the airflow path 220 reaches the heater assembly 100, it is redirected upward around the side of the heater assembly 100 and flows through the aerosol channel 224 to the aerosol outlet 226. It will be understood that other arrangements of the liquid storage section and airflow path can be implemented, such as those described later with respect to Figures 5 and 6.

[0025] The aerosol generating system 200 is configured such that a user can inhale or smoke through the mouthpiece 210 of the cartridge 202, thereby drawing an aerosol into their mouth through the aerosol outlet 226. When the user inhales through the mouthpiece 210 during operation, air is drawn through one or more air intake ports 222, along the airflow path 220, through the airflow channel 223, around the heater assembly 100, and along the airflow path 220 through the aerosol channel 224 to the aerosol outlet 226. The control circuit 208 controls the supply of power from the battery 206 to the cartridge 202 when the system is started. This controls the amount and characteristics of the vapor produced by the heater assembly 100. The control circuit 208 may include an airflow sensor (not shown), and the control circuit 208 may supply power to the heater assembly 100 when the airflow sensor detects user inhalation. This type of control arrangement is well established in aerosol generating systems such as inhalers and e-cigarettes. When the user inhales vapor onto the mouthpiece 210 of the cartridge 202, the heater assembly 100 is activated, generating vapor, which is drawn into the airflow path 220. The vapor is cooled within the airflow path 220 to form an aerosol, which is then inhaled into the user's mouth through the aerosol outlet 226.

[0026] Figure 5 is a schematic cross-sectional view of a portion of an aerosol generating system 300 according to another example of the present disclosure, showing the arrangement of the heater assembly 100 with respect to the airflow path 320 inside the aerosol generating system 300. For simplification, other components of the aerosol generating system are omitted from Figure 5. The heater assembly 100 in Figure 5 is identical to the heater assembly 100 in Figures 2 and 3. The aerosol generating system 300 includes a liquid storage portion 322 that holds a liquid aerosol-forming substrate and is in contact with the liquid-absorbing surface 102b of the porous body 102. The liquid aerosol-forming substrate is transported from the liquid storage portion 322 through the porous body 102 to the heating surface 102a, as indicated by arrow E. The vaporized aerosol-forming substrate is released from the heating surface 102a through the porous heating element 104. As indicated by arrow F, the mean vapor release direction is substantially perpendicular to the heating surface 102a of the porous body 102.

[0027] In the example shown in Figure 5, the heater assembly 100 is positioned below or to one side of the airflow channel or airflow path 320, which is defined by the airflow channel wall 324. As seen in Figure 5, the left end of the visible portion of the airflow path 320 receives airflow from an air intake (not shown), and the right end of the visible portion of the airflow path delivers airflow to an aerosol outlet (not shown). The heating surface 102a of the porous body 102 is positioned parallel to the airflow path 320 and faces into the airflow path 320. The heater assembly 100 is in fluid communication with the airflow path such that the airflow in the airflow path flows through the heater assembly 100 in the mean airflow direction, as indicated by arrow G. The heater assembly 100 and the airflow path 320 are arranged such that the angle θ between the average steam discharge direction F and the average airflow direction G is approximately 90 degrees, i.e., substantially perpendicular to the average airflow direction G. Since the average steam discharge direction F has no velocity, i.e., no directional component opposite to the average airflow direction G, momentum loss of the airflow is reduced. As a result, the tendency for recirculation and turbulence to occur within the airflow path 320 is reduced, and the steam is less likely to collide with the inner surface of the airflow channel wall 324.

[0028] Figure 6 is a schematic cross-sectional view of a portion of an aerosol generating system 400 according to another example of the present disclosure, showing another arrangement of the heater assembly 100 with respect to the airflow path 420 within the aerosol generating system 400. For simplification, other components of the aerosol generating system are omitted from Figure 6. The heater assembly 100 in Figure 6 is identical to the heater assembly 100 in Figures 2 and 3. The aerosol generating system 400 includes a liquid storage portion 422 that holds a liquid aerosol-forming substrate and is in contact with the liquid-absorbing surface 102b of the porous body 102. The liquid aerosol-forming substrate is transported from the liquid storage portion 422 through the porous body 102 to the heating surface 102a, as indicated by arrow E. The vaporized aerosol-forming substrate is released from the heating surface 102a through the porous heating element 104. As indicated by arrow F, the average steam release direction is substantially perpendicular to the heating surface 102a of the porous body 102.

[0029] In the example shown in Figure 6, the airflow channel or airflow path 420 is divided into a first airflow path section 420a and a second airflow path section 420b, which pass on both sides of the heater assembly 100. The first and second airflow path sections 420a and 420b merge into a third airflow path section 420c downstream of the heater assembly 100. The first and second airflow path sections 420a and 420b receive airflow from one or more air intakes (not shown), and the third airflow path section 420c delivers airflow to an aerosol outlet (not shown). The airflow path 420 is defined by the airflow channel wall 424. The heating surface 102a of the porous body 102 is positioned substantially perpendicular to the airflow path 420 and faces downstream of the airflow path 420. The heater assembly 100 is in fluid communication with the airflow path such that the airflow in the airflow path passes through the heater assembly 100 in the mean airflow direction, as indicated by arrow G.

[0030] The heater assembly 100 and the airflow path 120 are arranged such that the angle θ between the average steam discharge direction F and the average airflow direction G is less than 90 degrees. Upstream of the heating surface 102a of the porous body 102, the average airflow direction G passing through the heater assembly 100 is substantially the same as the steam discharge direction F. Along the airflow path 420, at a point corresponding to the heating surface 102a, the airflow path 420 begins to narrow, i.e., it begins to taper inward, and at this point, the angle θ of the average airflow direction G passing through the heater assembly 100 with respect to the steam discharge direction F changes to approximately 45 degrees. Downstream of the heating surface 102a of the porous body 102, within the third airflow path section 420c, the average airflow direction G of the merged airflows is again substantially the same as the steam discharge direction F. It will be understood that the narrowing, i.e., the tapered shape of the airflow path 420 can be omitted. In that case, the average airflow direction G passing through the heater assembly 100 is substantially the same as the steam discharge direction F.

[0031] The cross-sectional areas of the airflow paths 220, 320, and 420 in the aerosol generator shown in Figures 4, 5, and 6 are designed so that sufficient vapor from the liquid aerosol-forming substrate is taken into the airflow after it is released from the heater assembly 100. The airflow velocity is preferably greater than the vapor release velocity of the vapor released from the heater assembly to ensure proper vapor intake into the airflow paths 320 and 420. For example, for a vapor release velocity of 0.1 m / s to 0.7 m / s, an airflow velocity of approximately 1 m / s is desirable. According to a standard Cholesta fume extraction profile, 55 milliliters (55 cm³) are absorbed over a duration of 3 seconds. 3 The smoke intake of the ) is 18.3 cm 3 This represents a volumetric flow rate of 1 meter / second. Since the airflow velocity is the ratio of the volumetric flow rate to the cross-sectional area, an airflow velocity of 1 meter / second corresponds to 18.3 mm 2 This is obtained through an airflow path having a cross-sectional area X. In the aerosol generator shown in Figure 5, it can be seen that this cross-sectional area X is divided into the cross-sectional areas of two airflow path sections, 420a and 420b.

[0032] 18.3cm 3 A volumetric flow rate of 1 meter / second has been found to be sufficient to provide a desired throughput of 2.5 milligrams / second of aerosol-forming substrate vapor or aerosol for a typical liquid aerosol-forming substrate containing 44 percent glycerol, 44 percent propylene glycol, 10 percent water, nicotine, and flavoring agents. Furthermore, an airflow velocity of 1 meter / second has been found to be sufficient to adequately entrain the vapor into the airflow, reducing the likelihood of the vapor colliding with the airflow channel walls 324, 424 and forming condensates. In addition, an airflow velocity of 1 meter / second has been found not to cause significant cooling of the heat-generating element 104, nor to result in a decrease in the quantity or quality of the aerosol produced.

[0033] Figures 7 and 8 show schematic diagrams of an exemplary heater assembly 500 for an aerosol generation system. The heater assembly 500 includes a heating element 510 and a porous body 520. The heating element 510 is configured to form an aerosol by vaporizing an aerosol-forming substrate, such as a liquid aerosol-forming substrate. The heating element 510 is configured to convert electrical energy into thermal energy through the material resistance of the heating element 510 to electric current.

[0034] The porous body 520 is configured to transport the liquid aerosol-forming substrate to the heating element 510. In other words, the porous body 520 supplies the liquid aerosol-forming substrate to the heating element 510. The porous body 520 has a first end face and a second end face located on the opposite side. The first end face is the liquid absorption surface 530, and the second end face is the heating surface 540. In this example, both the liquid absorption surface 530 and the heating surface 540 are substantially flat surfaces. The porous body 520 also has a number of sides extending between the liquid absorption surface 530 and the heating surface 540. In this example, as will be described in more detail below, the porous body 520 has a first side 550 located on the opposite side of the second side 560 and a third side 570 located on the opposite side of the fourth side 580.

[0035] The porous body 520 has multiple pores. These multiple pores are interconnected to provide a fluid passage for the liquid aerosol-forming substrate through the porous body 520 from the liquid absorption surface 530 to the heating surface 540. The porous body 520 is formed from a material that does not chemically interact with the liquid aerosol-forming substrate. In this example, the porous body 520 is a porous ceramic body, which may be formed from, for example, one of Ca2SiO3 and SiO2 (or both Ca2SiO3 and SiO2). In another example, the porous body 520 may be, for example, a porous glass body.

[0036] The heating element 510 is positioned on the heating surface 540 of the porous body 520. In the examples of Figures 7 and 8, the heating element 510 is a porous film extending substantially over the entire heating surface 540.

[0037] The liquid-absorbing surface 530 of the porous body 520 has a different area than the heating surface 540 of the porous body 520. Specifically, in the examples of Figures 7 and 8, the area of ​​the heating surface 540 is smaller than the area of ​​the liquid-absorbing surface 530.

[0038] In the examples of Figures 7 and 8, the heating surface 540 has a smaller area than the liquid absorption surface 530 because the length of the heating surface 540 is shorter than the length of the liquid absorption surface 530. Additionally or alternatively, in another example, the heating surface 540 may have a smaller area than the liquid absorption surface 530 because the width of the heating surface 540 is smaller than the width of the liquid absorption surface 530.

[0039] In the examples shown in Figures 7 and 8, the porous body 520 is formed as a trapezoidal prism. Because the porous body 520 has a trapezoidal prism shape, both the first side surface 550 and the second side surface 560 have a trapezoidal shape, specifically an isosceles trapezoid, both the third side surface 570 and the fourth side surface 580 have a rectangular shape, and both the liquid absorption surface 530 and the heating surface 540 have a rectangular shape. In another example, the liquid absorption surface 530 and the heating surface 540 may have a square shape.

[0040] The porous body 520 is tapered from the liquid absorption surface 530 towards the heating surface 540. In other words, the cross-sectional area of ​​the porous body 520 gradually decreases from the liquid absorption surface 530 towards the heating surface 540. In the examples in Figures 7 and 8, the length of the porous body 520 decreases from the liquid absorption surface 530 towards the heating surface 540, and therefore it has a tapered shape.

[0041] In one example, the porous body 520 is formed from a sintered ceramic such as silicon carbide. The porous body 520 contains open pores. The open pores are pores in the long axis direction that extend throughout the porous body 520 from the liquid absorption surface 530 to the heating surface 540. The pore diameter of the porous body 520 changes between the liquid absorption surface 530 and the heating surface 540.

[0042] The porous body 520 includes a heating end and a liquid absorption end, with the heating surface 540 located at the heating end and the liquid absorption surface 530 located at the liquid absorption end. The porous body 520 includes a first average pore diameter at the liquid absorption end and a second average pore diameter at the heating end. The first average pore diameter is larger than the second average pore diameter.

[0043] The first pore diameter at the liquid absorption end is approximately 150 micrometers. The second pore diameter at the heating end is approximately 20 micrometers. The pore diameter changes linearly between the first and second pore diameters, thereby providing a pore diameter gradient between the liquid absorption end and the heating end of the porous body 520.

[0044] The pore structure and pore diameter gradient of the porous body 520 are obtained by etching pores into a portion of the silicon carbide.

[0045] Figure 9 shows a schematic plan view of an exemplary heater assembly 600 for an aerosol generating system. The heater assembly 600 includes a heating element 610 and a porous body 620. The porous body 620 can be made from any suitable ceramic material, such as the materials described in the arbitrary examples above. The heating element 610 is positioned on the heating surface 612 of the porous body 620. In the example of Figure 9, the heating element 610 is serpentine in shape and positioned on the heating surface 612. Similar to the exemplary heater assembly 500 in Figures 7 and 8, the heater assembly 600 in Figure 9 has a tapered shape, and the area of ​​the heating surface 612 is smaller than the area of ​​the liquid absorption surface (not visible) located on the bottom surface of the porous body 620 in the diagram shown in Figure 9. Both the liquid absorption surface and the heating surface 612 are square. Thus, the porous body 620 of the heater assembly 600 has the shape of a truncated pyramid with a square base. Each of the four longitudinal surface 613 of the porous body 620 has a trapezoidal shape of equal size.

[0046] The porous body 620 of the heater assembly 600 further includes a plurality of airflow guides 614 to guide the airflow toward the heating surface 612. Each of the four longitudinal surfaces 613 includes an airflow guide in the form of longitudinal grooves or slits provided within the surface 613. Each of the airflow guides 614 extends from the liquid absorption surface (not visible) toward the heating surface 612. The airflow guides 614 help to improve the airflow efficiency in the area of ​​the heater assembly 600. This arrangement is particularly beneficial when the airflow is substantially aligned with the direction of vapor release of the vaporized aerosol-forming substrate from the heating surface 612.

[0047] Figure 10 shows a heater assembly 700 for use in an aerosol generation system. The heater assembly 700 comprises a heating element 710 for vaporizing a liquid aerosol-forming substrate. The heater assembly 700 also comprises a porous body 720 for transporting the liquid aerosol-forming substrate to the heating element 710. The porous body 720 has a liquid absorption surface 721 and a heating surface 722 located on the opposite side. The heating element 710 is positioned on the heating surface 722 of the porous body 720. The porous body 720 can be made from any suitable ceramic material, such as the material described in the arbitrary example above.

[0048] The heating surface 722 of the porous body 720 is curved. In particular, the heating surface 722 of the porous body 720 is curved in a convex shape in a single transverse direction (first transverse direction).

[0049] The porous body 720 has a prism shape. When viewed in a cross-section along the long axis perpendicular to the curvature direction of the porous body 720, the heated surface 722 of the porous body 720 is shown as a circular arc. The porous body 720 has two planes of symmetry along the long axis.

[0050] The heating surface 722 of the porous body 720 has a width 723 in the first transverse direction that is substantially the same as the width of the porous body 720 in the first transverse direction, and also substantially the same as the width of the heater assembly 700 in the first transverse direction. The heating surface 720 of the porous body 720 has a width of approximately 5 millimeters in the first transverse direction.

[0051] The heating surface 722 of the porous body 720 has a length or thickness 724 of approximately 1 millimeter. The porous body 720 has a length or thickness 725 of approximately 3 millimeters.

[0052] The heating surface 722 of the porous material has a curvature of approximately 3.6 millimeters. The heating surface 722 of the porous material has a surface area of ​​approximately 28 square millimeters.

[0053] The porous body 720 has four longitudinal axis surfaces, or side walls, extending from the liquid absorption surface 721 to the heating surface 722. The four side walls are substantially perpendicular to the substantially flat liquid absorption surface 721. The liquid absorption surface 721 is square in shape.

[0054] The heating element 710 is a resistance heating element 710 and is curved. In particular, the curvature of the heating element 710 is substantially the same as the curvature of the heating surface 722 of the porous body 720. Therefore, the heating element 710 is also curved convexly in a single transverse direction.

[0055] The heating element 710 is positioned directly on the heating surface 722 of the porous body 720. The heating element 710 extends over most of the heating surface 722 of the porous body 720. Substantially the entire heating element 710 is in contact with the heating surface 722 of the porous body 720.

[0056] Figure 11 shows a schematic cross-sectional view of a heater assembly 800 for an aerosol generation system. The heater assembly 800 comprises a heating element 810, an insulating layer 820, and a porous body 830. The porous body 830 is configured to supply a liquid aerosol-forming substrate to the heating element 810. Specifically, the porous body 830 is configured to transport the liquid aerosol-forming substrate from a liquid storage section (not shown) to the heating element 810. The porous body 830 is configured to store some liquid aerosol-forming substrate before aerosolization by the heating element 810.

[0057] The porous body 830 is a rectangular block having a first end face and a second end face located on the opposite side. The first end face is a liquid absorption surface 834, and the second end face is a heating surface 833. In this example, both the liquid absorption surface 834 and the heating surface 833 are substantially flat surfaces. The porous body 830 also has a plurality of sides extending between the liquid absorption surface 834 and the heating surface 833. The porous body 830 has a first side 831 located on the opposite side of the second side 832, and a third side (not shown) located on the opposite side of the fourth side (not shown). The porous body 830 has a defined thickness between the liquid absorption surface 834 and the heating surface 833.

[0058] The porous body 830 has a plurality of open pores. The plurality of open pores are interconnected to provide a fluid passage for the aerosol-forming liquid through the porous body 830. The heater assembly 800 may be configured so that the liquid can pass through the fluid passage of the porous body 830 to the heating element 810, as shown by arrow 870. The porous body 830 is configured so that the fluid 870 passes from the liquid absorption surface 834 to the heating surface 833. The porous body 830 may include a material that does not chemically interact with the liquid aerosol-forming substrate. The porous body 830 includes ceramics. The porous body 830 includes, but is not limited to, one or more porous ceramics such as Al2O3, ZrO2, Si3N4, SiC, Ti3AlC2, BN, AlN, SiO2, MgO, mica, diatomaceous earth, silicates, silicides, and borides. Alternatively, the porous body 830 may comprise porous glass. It will be understood that the porous body 830 may have a different shape or may contain different materials.

[0059] The heating element 810 is configured to heat the liquid aerosol-forming substrate to form an aerosol. The heating element 810 is configured to convert electrical energy into thermal energy through the material resistance of the heating element 810 to electric current.

[0060] The heating element 810 has tracks that define a path across the heating surface 823 of the insulation layer 820. The heating element 810 defines a meandering track shape or an electrically parallel track shape across the heating surface 823 of the insulation layer 820. Three cross-sections through a portion of the tracks of the heating element 810 are shown in Figure 11. The multiple track portions are arranged such that the distances 818, 819 between at least two of the multiple track portions are in the range of 200 to 300 micrometers. The track portions are arranged at equal intervals. It will be understood that the distances 818, 819 between at least two of the multiple track portions do not have to be equal.

[0061] The heating element 810 is elongated and made of metals such as stainless steel, Ni-Cr alloy, NiCrAlY alloy, FeCrAl alloy (e.g., Kanthal), FeCrAlY alloy, Fe3Al alloy, Ni3Al alloy, NiAl alloy, and CuNi alloy. It will be understood that the heating element 810 may have different shapes or may contain different materials.

[0062] The heating element 810 is arranged along the outer surface of the insulation layer 820. The heating element 810 is in direct contact with the insulation layer 820.

[0063] The insulation layer 820 is arranged to enhance the insulation between the heat-generating element 810 and the porous body 830. The insulation layer 820 is arranged to insulate the heat-generating element 810 from the porous body 830 by extending across at least a portion of the heat-generating element 810. The insulation layer 820 is configured to reduce heat dissipation through the porous body 830, thereby improving energy efficiency by reducing energy loss.

[0064] The thermal insulation layer 820 is planar and has a size and shape configured to extend across the electric heating element 810. The thermal insulation layer 820 is configured to extend across the entire surface formed by the heating element 810. The thermal insulation layer 820 is configured to substantially cover the porous body 830 below the thermal insulation layer 120.

[0065] The thermal insulation layer 820 has a first end face 824 and a second end face 823 located on the opposite side. In this example, both the first end face 824 and the second end face 823 are substantially flat surfaces. The first end face 824 of the thermal insulation layer 820 is in direct contact with the porous ceramic body 830. The second end face 823 of the thermal insulation layer 820 is in direct contact with the heating element 810.

[0066] The thermal insulation layer 820 has a defined thickness between the first end face 824 and the second end face 823. The thickness of the thermal insulation layer 820 is thinner than the thickness of the porous body 830. The thermal insulation layer 820 may have a thickness of 0.1 mm to 2 mm, preferably 0.5 mm to 1.5 mm.

[0067] The thermal insulation layer 820 contains a material having a low thermal conductivity. The thermal insulation layer 820 contains a material having a lower thermal conductivity than the porous ceramic body 830, or consists of a material having such a low thermal conductivity. The thermal insulation layer 820 may have a higher porosity than the porous ceramic body 830. The thermal insulation layer 820 may contain materials such as alumina, zirconia, magnesium oxide-containing zirconia, glass ceramic, quartz, and porous polymers. It will be understood that the thermal insulation layer 820 may have different shapes or contain different materials.

[0068] Figure 12 shows a schematic cross-sectional view of another exemplary heater assembly 801 for an aerosol generating system. The heater assembly 801 in Figure 12 is identical to the heater assembly 800 in Figure 11, except that the heating element 815 comprises a porous heating element. The porous ceramic body 830 and the insulation layer 820 are as described in relation to the heater assembly 800 in Figure 11, and similar reference numerals are used to indicate similar components.

[0069] The heating element 815 extends to cover the area of ​​the second end face 823 of the heat insulating layer 820. The heating element 815 has a liquid-absorbing surface 814 and a heating surface 813. In this example, both the liquid-absorbing surface 814 and the heating surface 813 of the heating element 815 are substantially flat surfaces. The liquid-absorbing surface 814 of the heating element 815 is in direct contact with the heat insulating layer 120.

[0070] Figures 13a to 13c show schematic diagrams of different heating elements 910a to 910c for an aerosol generation system. Each heating element 910a to 910c comprises multiple tracks or track sections 917 arranged electrically in parallel. By being arranged electrically in parallel, the current flow is divided into separate parallel channels. These channels then merge again.

[0071] In the heating elements 910a to 910c shown in Figures 13a to 13c, each heating element 910a to 910c is equipped with a first connection pad 913 and a second connection pad 914. The first connection pad 913 and the second connection pad 914 are configured to allow connection to an external circuit. The openings or multiple openings 915 of the heating elements 910a to 910c separate each track 917. Each heating element 910a to 910c is equipped with a branching section, in which the current is divided from the first connection pad 913 to each track 917 that defines each electrically parallel path. Each heating element 910a to 910c is equipped with a converging section, in which the current merges from each track 917 that defines each electrically parallel path to the second connection pad 914.

[0072] Figures 13a to 13c show three different arrangements relating to electrically parallel-arranged tracks or track sections. In Figure 13a, four electrically parallel paths are defined by separating four tracks 917 with three openings 915. In Figure 13b, two electrically parallel paths are defined by separating six track sections 917 with one opening 915. In Figure 13b, each electrically parallel path defines a meandering path between a first connection pad 913 and a second connection pad 914. In Figure 13c, four pairs of electrically parallel paths are defined by separating eight track sections 917 with four openings 915. Each pair of electrically parallel paths in Figure 13c is separated by an intermediate connection section 916, and three intermediate connection sections are shown in Figure 13c.

[0073] By having electrically parallel tracks or track sections, even if one track section is defective, the current can be redistributed and still flow through the heating elements 910a-910c, meaning the electrical connection between the first connection pad 913 and the second connection pad 914 is not broken. This has the advantage of increasing the number of fume extractions before the heater completely fails, potentially extending the heater's lifespan to the end of the device's life. In contrast, in a simple meandering heater that defines a single electrical path between the first connection pad 913 and the second connection pad 914, if a part of the meandering heating element is damaged, the heating element will stop operating based on the increased local resistance at the damaged or defective location. A defect in a simple meandering heater is that it causes an increase in local resistance. Increased local resistance causes increased power dissipation. Increased power dissipation increases the resistance until failure.

[0074] The inventors have also found that electrically parallel-arranged parallel tracks or parallel track sections, as described with reference to Figures 13a to 13c, have a surprising additional advantage. In this arrangement, even if one track section fails, the heating element will still operate, and for an initial transient period, the failure of one track or track section will result in a greater energy density on the remaining tracks or track sections, allowing it to operate in an advantageous manner. In such a case, throughput is improved because the same power is supplied but only a smaller area is operating. Although such failure will increase the current on the undamaged tracks or track sections and may ultimately degrade the user experience, the device or cartridge may include a mechanism to warn the user of the possibility of the heater assembly falling below optimal performance in the future.

[0075] Such a mechanism relies on the following principle: The total electrical resistance of the heating element depends on the following factors: 1) The number of parallel heating tracks (the more parallel tracks there are, the lower the total resistance), 2) The cross-sectional area of ​​the parallel heating tracks (either width or thickness (or both)) (the larger the cross-sectional area, the lower the resistance), 3) The length of the parallel heating tracks (the longer the tracks, the greater the resistance), 4) When the heating element is porous, adjust the porosity of the heating element (the larger the porosity, the greater the resistance). 5) A specific chemical or material composition (e.g., an alloy with doping).

[0076] The overall total heat resistance Rout for an arrangement Ri consisting of multiple heat sources or track portions (i) arranged in parallel such that the currents in at least two adjacent tracks or track portions flow in the same direction is given by Equation 1.

number

[0077] The behavior of a parallel track heating element when one heating element fails can be considered by referring to a heating element with four parallel heating tracks, as shown in Figure 13a. Each heating track has a resistance of 3 ohms. The total resistance of the heating element is 0.75 ohms, calculated using Equation 1.

[0078] When one heating track begins to fail, the resistance of the failed heating track increases. The total resistance of the heating element also begins to increase, following a linear relationship with the resistance of the failed heating track. However, as the resistance of the heating element continues to increase, it asymptotically approaches a constant resistance value. At this constant resistance value, the effect of the failed heating track on the resistance of the heating element is terminated. In this example, if each of the non-failed heating tracks has a resistance of 3 ohms, the total resistance of the heating element asymptotically approaches 1 ohm when the failed heating track can be considered an open circuit (i.e., no more current can flow through it). In this example, when one track fails, only three tracks remain to calculate the total resistance of the heating element.

[0079] To examine the behavior of such a heating element, we consider a supply voltage of 3.5 volts and a target power of 5.5 watts. In this example, the non-faulting parallel heating track remains with an initial resistance of 3 ohms. In the faulty track, the total maximum current decreases as the resistance increases. In the faulty track, after the failure, the current decreases to zero. The current flowing through the non-faulting parallel track remains substantially constant even as the resistance of the faulty track increases (ignoring resistance changes due to temperature rise).

[0080] Similar behavior is observed at maximum power. After a heating track fails, the total power decreases. However, in this example, the maximum power remains above the target of 5.5 watts despite the failure of one heating track.

[0081] In contrast to heat elements with a film, the increase in the overall heat resistance of a parallel track heat element can be monitored by control electronics. In a film heat element, the damaged area may expand over time until failure occurs because the current density across the film heat element (perpendicular to the flow of current) increases in the damaged area, generating more power and raising the local temperature. This locally increases the resistance of the film heat element, causing the temperature to rise further (i.e., positive feedback) until dielectric breakdown occurs. In contrast, in a parallel track heat element, the increase in the overall heat resistance can be monitored by control electronics. The aerosol generating system may be configured so that, when a predetermined threshold is reached, the device or system informs the user via a user interface that the heater assembly should be replaced.

[0082] The aerosol generation system may also be configured to extend the lifespan of the parallel track heating elements. The aerosol generation system may include a control circuit configured to adjust the power supplied to the heater after detecting a failure in a heating track, for example, by a feedback loop. The control circuit may be configured to supply a pulse-width modulation ("PWM") signal to control the power supplied to the heater. The control circuit may adjust the power supplied to the heater by adjusting the duty cycle of the pulse-width modulation signal. In one example, the control circuit may be configured so that the duty cycle is 33.7 percent when the heating tracks are in normal condition. The duty cycle may increase to 44.9 percent when one of the heating tracks fails. When one of the heating tracks fails, the power density (heating power generated by the surface area) increases, and the thermal efficiency of the heater body increases. Therefore, the proper operation of the heater is not impaired even if one heating track fails. Similar results are obtained when a second heating track fails. The control circuit may be configured so that the duty cycle increases further (to 67.4 percent in this example). Therefore, the heating element with four parallel heating tracks can still operate at the nominal condition of 5.5 watts even if two of these heating tracks fail, because the duty cycle remains below 100 percent.

[0083] The control circuit may be configured such that, after a parallel heating track fails, the control circuit can evaluate the condition of the heating elements (i.e., the number of failed heating tracks) based on the change in the nominal total resistance of the heating elements. The control circuit may also be configured such that, after a predetermined number of heating tracks have failed, the device can inform the user that the heater assembly should be replaced.

[0084] Figures 14a and 14b show schematic diagrams of current flow 909 around the corners of a heating element track. Figure 14a is a schematic diagram of current flow 909a around a known heating element, in which the track portion 917a defines a path with a bend, and the inner edge of the bend has an acute corner. Thus, in the track portion 917a, the current flow illustrated by arrow 909a becomes concentrated (i.e., the current density increases) in order to follow the path of least resistance. This concentration occurs at the inner edge of the corner. Current concentration can increase the local temperature and may lead to the presence of a hot spot at the corner. Hot spots are undesirable because they can negatively affect the efficiency and reliability of the heating element. Hot spots occur despite the fact that the local resistivity of the heater track material may increase based on the local temperature rise (which guides the current flow to the lower-resistance path).

[0085] Figure 14b is a schematic diagram of the current flow 909b around the heating element, in which the track portion 917b defines a path with a curved section, and the inner edge of the curved section is curved. In such a track portion 917b, the current flow 909b does not form localized hot spots.

[0086] In contrast to the track shape shown in Figure 14a, the current flow 909b in the more smoothly curved track section 917b, as shown in Figure 14b, remains more uniformly distributed across the heated track 917b, as illustrated by the dashed arrow 909b. The current flow 909b is induced to flow more evenly, avoiding current concentration at any particular point. This limits the occurrence of hot spots. The heated track 917b may have an electrical resistivity gradient perpendicular to the current flow within the corner, such that the electrical resistivity is higher in the inner part of the corner and lower in the outer part of the corner. Such a gradient is advantageous in offsetting localized high current densities and reducing the occurrence of hot spots.

[0087] For the purposes of this specification and the appended claims, unless otherwise indicated, all numerical values ​​representing quantities, amounts, percentages, etc., should be understood in all instances as being modified by the term “approximately.” Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges within them, which may or may not be specifically listed herein. Thus, in this context, number A is understood as A ± 5 percent (5%). In this context, number A may be considered to include numerical values ​​that fall within the general standard error of the measured value of the characteristic modified by number A. Number A may deviate by the percentages listed above, provided that in some cases, such as those used in the appended claims, the amount by which A deviates does not substantially affect the fundamental and novel characteristics of the claimed invention. Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges contained within them, whether or not they are specifically listed herein.

[0088] According to one example of the present disclosure, an aerosol generating system is provided which includes a heater assembly. The heater assembly comprises a heating element for vaporizing a liquid aerosol-forming substrate and a porous body for transporting the liquid aerosol-forming substrate to the heating element. The porous body has a liquid-absorbing surface and a heating surface. The heating element is positioned on the heating surface of the porous body. The heating element is fluid-permeable, so that when in use, vapor is released from the heater assembly in the mean vapor discharge direction. The aerosol generating system further comprises an air intake and an aerosol outlet. The air intake defines an airflow path through the aerosol generating system by fluid communication with the aerosol outlet. The heater assembly is positioned to fluidly communicate with the airflow path such that air flows through the heater assembly in the mean airflow direction. The heater assembly and the airflow path are positioned such that the angle between the mean vapor discharge direction and the mean airflow direction is less than 135 degrees.

[0089] As used herein, the term “placed on top of” includes arrangements in which the heating element is in direct contact with the heating surface of the porous body, and arrangements in which the heating element is indirectly placed on the heating surface of the porous body, i.e., arrangements in which another component or layer may be placed between the heating element and the heating surface.

[0090] As used herein, the term “angle between mean steam discharge direction and mean airflow direction” refers to the angle between the direction of steam discharge from the heater assembly and the direction of airflow within the airflow path. For example, an angle of zero degrees means that the airflow and steam discharge are moving in the same direction, while an angle of 180 degrees means that the direction of airflow and the direction of steam discharge are directly opposite each other.

[0091] Advantageously, by arranging the heater assembly and airflow path such that the angle between the average vapor discharge direction and the average airflow direction is less than 135 degrees, the average airflow direction does not directly face the average vapor discharge direction. Therefore, the momentum of the vapor and airflow does not decrease to the same extent as when the average airflow direction directly faces the average vapor discharge direction. This reduces the tendency for recirculation and turbulence to occur within the airflow path, and the vapor is less likely to collide with the inner surface of the aerosol generation system. Consequently, aerosol condensation inside the aerosol generation system is less likely to occur.

[0092] The average vapor discharge direction may be substantially perpendicular to the heating surface. As used herein, the term “substantially perpendicular” means 90 degrees plus or minus 10 degrees, preferably plus or minus 5 degrees.

[0093] The advantage of having the average vapor discharge direction substantially perpendicular to the heating surface is that, since the vapor is discharged substantially perpendicular to the heating surface of the porous material, it becomes easy to orient the average vapor discharge direction relative to the average airflow direction. Therefore, by appropriately orienting the heater assembly with respect to the airflow in the airflow path, or vice versa, a desired angle between the average vapor discharge direction and the average airflow direction can be achieved.

[0094] The heater assembly may be positioned along the airflow path. The heating surface of the heater assembly may be in fluid communication with the airflow path. The heating surface may be positioned substantially parallel to the airflow path. The heating surface may be positioned substantially parallel to the mean airflow direction. The heating surface may be positioned substantially perpendicular to the airflow path. The heating surface may be positioned substantially perpendicular to the mean airflow direction. The heating surface may face downstream of the airflow path. The heater assembly may be positioned on one side of the airflow path. The heater assembly may be positioned inside the airflow path. The airflow path may be a spit so that air flows through two or more surfaces of the heater assembly. The airflow path may include a first airflow channel positioned substantially parallel to the heating surface. The airflow path may include a second airflow channel positioned substantially perpendicular to the heating surface. The second airflow channel may start at the heating surface.

[0095] The heater assembly and the airflow path may be arranged such that the angle between the average steam discharge direction and the average airflow direction is less than 110 degrees, preferably less than 100 degrees.

[0096] The heater assembly and the airflow path may be arranged such that the angle between the mean vapor discharge direction and the mean airflow direction is approximately 90 degrees. This arrangement causes the vapor to be discharged at an angle substantially perpendicular to the mean airflow direction. Since the mean vapor discharge direction does not have a velocity, i.e., a directional component, opposite to the airflow direction, momentum loss of the airflow is reduced. This reduces the tendency for recirculation and turbulence to occur within the airflow path, and the vapor is less likely to collide with the inner surface of the aerosol generation system. Furthermore, the entrainment of vapor into the airflow is improved. Therefore, aerosol condensation inside the aerosol generation system is less likely to occur.

[0097] The heater assembly and the airflow path may be arranged such that the angle between the mean vapor discharge direction and the mean airflow direction is less than 90 degrees. In this arrangement, the mean vapor discharge direction does not have a velocity, i.e., a directional component opposite to the airflow direction, but actually has a velocity and directional component in the same direction as the mean airflow direction. Therefore, momentum loss of the airflow is further reduced. This reduces the tendency for recirculation and turbulence to occur in the airflow path, and vapor is less likely to collide with the inner surface of the aerosol generation system. Furthermore, the entrainment of vapor into the airflow is improved. Therefore, aerosol condensation inside the aerosol generation system is less likely to occur.

[0098] The heater assembly and the airflow path may be arranged such that the angle between the average steam discharge direction and the average airflow direction is approximately 45 degrees. Alternatively, the heater assembly and the airflow path may be arranged such that the angle between the average steam discharge direction and the average airflow direction is less than 45 degrees.

[0099] The heater assembly and the airflow path may be arranged such that the mean vapor discharge direction and the mean airflow direction are substantially the same. In this arrangement, since the mean vapor discharge direction and the mean airflow direction are the same, there is virtually no momentum loss in the airflow. This reduces the tendency for recirculation and turbulence to occur within the airflow path, and makes it less likely for vapor to collide with the inner surface of the aerosol generation system. Furthermore, the entrainment of vapor into the airflow is improved. Therefore, aerosol condensation inside the aerosol generation system becomes less likely.

[0100] The porous body may be provided with at least one airflow guide to direct the airflow toward the heating surface. Advantageously, this improves aerosol entrainment into the airflow by assisting in guiding the airflow toward the location where the vapor is released.

[0101] The air intake may be located distal to the heater assembly. The air intake may be located within the area of ​​the heater assembly; for example, the air intake may be positioned along the length of the aerosol generating system substantially corresponding to the position of the heater assembly.

[0102] The terms “distal,” “proximal,” “upstream,” and “downstream” are used herein to describe the relative positions of components or parts of components of an aerosol generating system. The aerosol generating system according to this disclosure has a proximal end from which aerosol is drawn out of an article or device for delivery to a user during use, and a distal end located on the opposite side. The proximal end of the aerosol generating system may also be referred to as the mouth end. During use, the user inhales the proximal end of the aerosol generating system to inhale the aerosol generated by the aerosol generating system. The terms upstream and downstream refer to the direction of airflow or aerosol movement through the aerosol generating system when the user inhales the proximal end of the aerosol generating system. The proximal end of the aerosol generating system is located downstream of the distal end of the aerosol generating system.

[0103] The cross-sectional area of ​​the airflow path in the heater assembly region may be configured such that, during use, the airflow velocity in the heater assembly region is 0.1 m / s to 2 m / s, preferably 0.5 m / s to 1.5 m / s, and more preferably about 1 m / s. The cross-sectional area of ​​the airflow path in the heater assembly region may be 9.15 square millimeters to 183 square millimeters. This range of cross-sectional area provides an airflow velocity in the heater assembly region of 0.1 m / s to 2 m / s with 55 milliliters (55 cubic centimeters) of smoke extraction over a duration of 3 seconds, based on a standard Cholesta smoke extraction profile. Such smoke extraction corresponds to a volumetric flow rate of 18.3 cubic centimeters / second through the airflow path. This range of airflow velocity has been shown to effectively entrain vapors released from heating elements of various configurations without excessively cooling the heating element.

[0104] A porous body may have multiple interconnected open pores. A porous material may have a porosity of 20% to 80%.

[0105] The porous body may have any suitable geometric shape. For example, the porous body may be cubic or rectangular, or disc or cylindrical, or a combination of the shapes described above. The heating surface of the porous body may be flat or curved. The liquid-absorbing surface of the porous body may be flat or curved. The liquid-absorbing surface of the porous body may have recesses or wells through which at least a portion of the liquid aerosol-forming substrate is absorbed.

[0106] The porous material may be substantially incompressible.

[0107] The porous body may be made from any suitable material. The porous body may be made from a material having a thermal conductivity of less than 150 W / mK, preferably less than 100 W / mK, and more preferably less than 60 W / mK. The porous body may be made from a non-electrically conductive material.

[0108] The porous body may comprise a porous ceramic body. The porous body may comprise a ceramic. The porous body may comprise any suitable inert ceramic or biocompatible ceramic. Examples of suitable ceramics, but not limited to, include Al2O3, ZrO2, Si3N4, SiC, Ti3AlC2, BN, AlN, SiO2, MgO, mica, diatomaceous earth, silicides, borides, glass, or combinations thereof. The advantage of using ceramic materials is that the heater assembly is thermally stable at its typical operating temperature and generally has a significantly higher thermal decomposition temperature than that of conventional wicks. This may help reduce the risk of unwanted byproducts being generated during heating.

[0109] The porous body may include a porous glass body.

[0110] Porous bodies may include capillary materials that transport liquids through the material by capillary action. Porous bodies may have a fibrous structure or a porous structure. Porous bodies may comprise bundles of capillaries. For example, a porous body may comprise a plurality of fibers or threads, or other microporous tubes. Porous bodies may comprise fibers or threads made of cotton, or treated cotton such as acetylated cotton. Other suitable materials can also be used, for example, ceramic or graphite-based fibrous materials, or materials made from spun, drawn, or extruded fibers such as fiberglass, cellulose acetate, or any suitable heat-resistant polymer.

[0111] The porous material may be composed of a monolithic material or a hybrid material.

[0112] The thickness of the porous body may be configured such that heat loss due to conduction to the liquid held by the liquid storage section is negligible. The thickness of the porous body may vary depending on the thermal properties of the material from which the porous body is made, and on the thermal properties of the liquid transported by the porous body. The porous body may have a thickness of 1 mm to 10 mm, preferably 2 mm to 8 mm, and more preferably 3 mm to 6 mm.

[0113] The heating element may be configured to have a vapor release rate in the range of 0.1 meters / second to 1 meter / second. While keeping factors such as the power supplied to the heating element constant, the vapor release rate can be adjusted by adjusting the shape of the heating element, as will be described later.

[0114] The heating element may consist of a non-porous heating element or a track. As mentioned above, a non-porous heating element accumulates vapor pressure below the heating element, which increases the vapor release rate.

[0115] The heating element may be porous. The heating element may have a porosity of 20% to 80%.

[0116] The heating element may comprise an electrical resistance heating element. The heating element may be made from any suitable conductive material. Suitable materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilide), carbon, graphite, metals, metal alloys, and composite materials made from ceramic and metallic materials. Such composite materials may include doped or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Suitable alloys include stainless steel, constantan, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel, iron, cobalt, and stainless steel-based superalloys, Timetal®, iron-aluminum alloys, and iron-manganese-aluminum alloys. Timetal® is a registered trademark of Titanium Metals Corporation.

[0117] In one example, the heating element may be made from a metal alloy selected from one or more of the following: Ni-Cr alloy, NiCrAlY alloy, FeCrAl alloy (e.g., Kanthal), FeCrAlY alloy, Fe3Al alloy, Ni3Al alloy, NiAl alloy, and CuNi alloy.

[0118] In another example, the heating element may be made from stainless steel, such as 300 series stainless steels like AISI 304, 316, 304L, or 316L.

[0119] In another example, the heating element may be made from electroceramics including, but not limited to, MoSi2, doped SiC, indium tin oxide (ITO), lanthanum-doped strontium titanate (SLT), yttrium-doped strontium titanate, or a combination thereof.

[0120] The heating element may comprise a doped portion of a porous material. The porous material may be doped such that the portion of the porous material that functions as a heating element is conductive. Doping the porous material may be advantageous in that it does not change the porosity of the porous material. This may be more preferable to other known techniques for forming heating elements, such as those involving the deposition of the heating element by thin-film or thick-film techniques, which can particularly reduce the porosity of the porous material. The doped portion may have a thickness of 5 to 100 micrometers. The thickness of the doped portion may be thicker if the cross-sectional area of ​​the heating element is smaller or if a greater heating resistance is required. The dopant used to dope the porous material may be an n-type dopant or a p-type dopant. The dopant may be nitrogen, phosphorus, aluminum, or boron, but is not limited to these. The interface between the heating element and the porous material may comprise a portion of the partially doped porous material.

[0121] The heating element may have a porous layer made of a conductive material. Advantageously, a heating element with a porous layer made of a conductive material allows electric current to flow through it, enabling resistance heating of the heating element. Furthermore, the pores in its porous structure allow steam to permeate and move through the heating element. Thus, steam is released through the porous heating element. This prevents an increase in steam pressure below the heating element and prevents high-speed steam release at the sides of the heating element. The inventors have found that this configuration generates steam throughout the entire heating element and achieves a low steam release velocity of approximately 0.1 meters / second. Such a low steam release velocity means that the steam is easily carried by the airflow, thus reducing steam collisions with the inner wall of the aerosol generation system.

[0122] The heating element may include a porous metal film. The porous metal film may be a thick film, that is, the porous metal film may have a thickness of 5 μm to 50 μm, preferably 10 μm to 30 μm, and more preferably 15 μm to 25 μm. The porous metal film may be a thin film, that is, the porous metal film may have a thickness of less than 5 μm, preferably less than 3 μm, and more preferably less than 2 μm.

[0123] The heating element may include a metal foam. The metal foam may have a thickness of less than 100 μm, preferably less than 50 μm, and more preferably less than 30 μm.

[0124] The heating element may define a heating area. The heating area may cover at least a portion of the heating surface. The heating area may cover substantially the entire heating surface. The heating area may be any suitable shape. The heating area may be square or rectangular, or it may be circular or elliptical. The heating area may be 30 mm 2 Less than 20 mm, preferably 20 mm 2 Less than, more preferably 15 mm 2 Less than 10 mm, more preferably 10 mm2 Less than, or may be.

[0125] The heating element is 0.3 W / mm 2 ~2 W / mm 2 Preferably 0.5 W / mm 2 ~1.5 W / mm 2 It may be configured to provide a power density of. The heating element is at least 0.5 W / mm 2 Preferably at least 1 W / mm 2 It may be configured to provide a power density of.

[0126] The inventors have advantageously found that the power density supplied to the heating element is a more important factor in determining the amount of aerosol generated compared to the power itself supplied to the heating element. As used herein, the term "power density" refers to the amount of power supplied to the heating element per unit area being heated.

[0127] The first dimension of the heating region of the heating element may be in the range of 2 mm to 10 mm. The second dimension of the heating region of the heating element may be in the range of 2 mm to 10 mm. The dimensions of the heating region of the heating element, i.e., the heating surface, may be, for example, 5 mm × 6 mm, or 5 mm × 4 mm, or 5 mm × 3 mm, or 5 mm × 2 mm.

[0128] The heating element may have an electrical resistance at room temperature of 0.5 Ω to 1.5 Ω, 0.7 Ω to 1.3 Ω, or preferably about 1 Ω.

[0129] The electric heating element may comprise discrete, solid, pre-formed components. The electric heating element may have any suitable shape or form. Examples of suitable shapes and forms include, but are not limited to, strips, flakes, filaments, wires, meshes, flat spiral coils, fibers, or fabrics.

[0130] The electric heating element may be formed from a conductive material deposited onto the heating surface. As used herein, the term "conductive material" refers to 1×10-2 This refers to a material having a resistivity of Ωm or less. As used herein, the term “deposited” means applied as a layer or coating by a physical or chemical process, for example, in the form of a liquid, plasma, or vapor, in which case the layer or coating is not simply laid on or fixed to a porous body as a pre-formed solid component, but subsequently condenses or aggregates to form an electrically heating element. The heating element may be deposited or patterned by thick-film techniques such as screen printing, inkjet printing, aerosol jet printing, or LDS (Laser Direct Structuring). A template may be added to the heating element material, which will be removed during sintering, thereby forming a porous structure that enhances liquid vaporization and reduces vapor release rate. The heating element may be deposited or patterned by thin-film techniques such as PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), or similar methods, such as vapor deposition or sputtering.

[0131] The heater assembly may further include a first electrical contact and a second electrical contact connected to the heating element. Each electrical contact may be located on both sides of the heating surface. The heating element may extend between the electrical contacts. The heating element may form an electrical connection between the electrical contacts.

[0132] Electrical contacts may be formed from any suitable material. Examples of suitable materials for electrical contacts include, but are not limited to, copper, zinc, and gold.

[0133] In one example, the first and second electrical contacts may be formed from a conductive material deposited directly onto the heated surface of a porous body.

[0134] The heating element and the porous body may be formed integrally. By forming the heating element integrally with the porous body, a stronger and more reliable connection between the heating element and the porous body may be advantageously provided. This may also advantageously assist in improving heat transfer between the heating element and the porous body.

[0135] Integrating the heating element with the porous body also offers the advantage of providing a heating element that is easier to manufacture with greater reliability, which may result in a more energy-efficient heating element that can generate aerosols more stably. This may provide users of the aerosol generation system with an improved and more enjoyable experience. This arrangement may also help reduce the likelihood of users experiencing dry heating or dry fumes.

[0136] The advantage of integrally forming the heating element with the porous body is that it helps mitigate manufacturing tolerance issues, such as those encountered in core heaters and coil heaters, as well as in other configurations where the heating element is detached from the liquid transport element. Because the dimensions and placement of the heating element relative to the porous body are fixed, more stable aerosol generation is facilitated. This is because the fixed position of the heating element relative to the porous body facilitates the supply of the liquid aerosol-forming substrate to the heating element. This also helps prevent unnecessary heat loss and contributes to improved energy efficiency.

[0137] By integrally forming the heating element with the porous body, the resulting aerosol generation system may benefit from reduced material requirements. This is because the need for intermediate components to fix the heating element to the porous body can be reduced or completely eliminated. Material savings can lead to overall cost savings for the aerosol generation system. An additional benefit of reduced material requirements in the overall aerosol generation system is the provision of a more sustainable and environmentally friendly solution.

[0138] Because the heating element is integrally formed with the porous body, the heating surface of the porous body does not need to be a clearly defined surface. The porous body and the heating element may be made from a single monolithic portion of the porous material. In this case, the heating element may be a portion of the porous material configured to generate heat. As will be described in more detail below, this may be achieved, for example, by doping a portion of the porous material or by diffusing a conductive material into the porous material. Therefore, the heating surface of the porous body may represent the interface between the porous material configured to transport the liquid aerosol-forming substrate and the porous material configured to generate heat. Depending on the method by which the heating element is formed, the heating surface of the porous body may be a gradual interface between the porous material configured to transport the liquid aerosol-forming substrate and the porous material configured to generate heat.

[0139] Alternatively, the porous body and the heating element may be formed as two separate components assembled together.

[0140] The heating element may be bonded to the heating surface of the porous body. An advantage of providing a heater assembly in which the heating element is bonded to the heating surface of the porous ceramic body is that a robust and reliable connection can be established between the heating element and the porous ceramic body. This may, advantageously, help improve heat transfer between the heating element and the porous ceramic body.

[0141] The heating element may have a tapered cross-sectional shape. The heating element may be tapered in the direction from the liquid absorption surface to the heating surface.

[0142] The liquid-absorbing surface of the porous material may have a different area from the heating surface of the porous material.

[0143] A heater assembly with a heating surface having the same area as the liquid absorption surface may be inefficient because the heat generated by the heater is not used to vaporize the aerosol-forming substrate. Inefficient heater assemblies lead to a decrease in aerosol throughput.

[0144] Advantageously, by providing a porous body in which the heating surface and the liquid absorption surface have different areas, the throughput of aerosols that can be generated by the heater assembly may be improved compared to a heater assembly in which the heating surface has the same area as the liquid absorption surface.

[0145] For example, in a heater assembly where the heating surface area of ​​the porous material is smaller than the liquid absorption surface area of ​​the porous material, the conduction of heat from the heating element to the liquid absorption surface and further to the liquid storage area may be reduced. A relatively small heating surface provides only a small heat transfer area for conducting heat from the heating element to the porous material and further to the liquid absorption surface.

[0146] By reducing heat loss from the heating element to the majority of the porous material, heating efficiency can be increased because, as a result, much of the thermal energy provided by the heating element can be used to vaporize the aerosol-forming substrate. Consequently, a porous material shaped so that the heating surface has a smaller area than the liquid-absorbing surface can increase the throughput of aerosols generated by the heater assembly.

[0147] For example, in a heater assembly where the area of ​​the porous liquid absorption surface is smaller than the area of ​​the porous heating surface, the smaller area of ​​the liquid absorption surface may reduce the heat flow through the aerosol-forming substrate via heat conduction from the heating element to the liquid absorption surface.

[0148] By reducing the heat flow from the heating element to the liquid absorption surface, heating efficiency may be increased, as a result, more of the thermal energy provided by the heating element can be used to vaporize the liquid aerosol-forming substrate. Consequently, a porous body shaped such that the liquid absorption surface has a smaller area than the heating surface may provide increased heating efficiency, which may increase the throughput of the aerosol generated by the heater assembly.

[0149] Increased heating efficiency may reduce power consumption when using the heater assembly.

[0150] The heating surface area of ​​the porous material may be smaller than the liquid-absorbing surface area of ​​the porous material. Alternatively, the liquid-absorbing surface area of ​​the porous material may be larger than the heating surface area of ​​the porous material.

[0151] Advantageously, when the porous body is shaped such that the heating surface has a smaller area than the liquid absorption surface, the conduction of heat from the heating element to the liquid absorption surface and further to the liquid storage portion may be reduced. The relatively small heating surface provides a small heat transfer area for conducting heat from the heating element to the porous body and further to the liquid absorption surface.

[0152] By reducing heat loss from the heating element to the majority of the porous material, heating efficiency may be increased, as a result, more of the thermal energy provided by the heating element can be used to vaporize the aerosol-forming substrate. Consequently, a porous material shaped so that the heating surface has a smaller area than the liquid-absorbing surface can increase the throughput of the aerosol generated by the heater assembly.

[0153] Advantageously, a porous body shaped such that the heating surface has a smaller area than the liquid absorption surface may reduce the area of ​​the heating surface that is not sufficiently far from the heating element in order to allow the aerosol-forming substrate being transported to the heating surface to be vaporized. In other words, the size and shape of the heating surface may more closely match the size and shape of the heating element. As a result, more of the liquid aerosol-forming substrate may be transported from the liquid absorption surface to the heating surface region closer to the heating element, thereby allowing more of the liquid aerosol-forming substrate on the heating surface to be vaporized. More vaporized liquid aerosol-forming substrate may increase the aerosol throughput generated by the heater assembly. Furthermore, this arrangement may allow for maximization of the power density at the heating surface, which also improves heating efficiency.

[0154] Advantageously, a liquid absorption surface having a larger area than the heating surface may allow the liquid absorption surface to receive a larger volume of liquid aerosol substrate from the liquid storage portion. As a result of the relatively small area of ​​the heating surface, the flow rate of the liquid aerosol-forming substrate to the heating element may be greater than that of a typical heater assembly when the liquid aerosol-forming substrate is transported through the porous material toward the heating surface. The higher flow rate of the liquid aerosol-forming substrate at the heating element may increase the throughput of the aerosol generated by the heater assembly.

[0155] The ratio of the heating surface area of ​​the porous material to the liquid-absorbing surface area may be 0.9 or less. The ratio of the heating surface area of ​​the porous material to the liquid-absorbing surface area may be at least 0.1. The ratio of the heating surface area of ​​the porous material to the liquid-absorbing surface area may be between 0.1 and 0.9.

[0156] The heating surface area of ​​the porous material may be larger than the liquid-absorbing surface area of ​​the porous material. Alternatively, the liquid-absorbing surface area of ​​the porous material may be smaller than the heating surface area of ​​the porous material.

[0157] Advantageously, when the porous material is shaped such that the liquid absorption surface has a smaller area than the heating surface, the smaller area of ​​the liquid absorption surface may reduce the flow of heat through the aerosol-forming substrate via heat conduction from the heating element to the liquid absorption surface. By reducing the flow of heat from the heating surface to the liquid absorption surface, more of the thermal energy provided by the heating element can be used to vaporize the liquid aerosol-forming substrate, which may result in increased thermal efficiency. Consequently, a porous material shaped such that the liquid absorption surface has a smaller area than the heating surface may provide increased heating efficiency, which may increase the throughput of aerosols generated by the heater assembly.

[0158] Advantageously, a porous body shaped such that the heating surface has a smaller area than the liquid absorption surface may reduce the area of ​​the heating surface that is not sufficiently far from the heating element in order to allow the aerosol-forming substrate being transported to the heating surface to be vaporized. In other words, the size and shape of the heating surface may more closely match the size and shape of the heating element. As a result, more of the liquid aerosol-forming substrate may be transported from the liquid absorption surface to the heating surface region closer to the heating element, thereby allowing more of the liquid aerosol-forming substrate on the heating surface to be vaporized. More vaporized liquid aerosol-forming substrate may increase the throughput of aerosols generated by the heater assembly.

[0159] The heating surface of the porous body may be convex in one or both of the first and second transverse directions. The first transverse direction may be perpendicular to the second transverse direction.

[0160] Advantageously, by providing a porous body having a heating surface that is convex in one or both of the first and second transverse directions, it may be possible to increase the surface area of ​​the heating surface without increasing the width of the heating surface. This may increase the efficiency of the aerosol generating system when vaporizing the liquid aerosol-forming substrate, while helping to avoid the need to redesign other components of the aerosol generating system to accommodate the porous ceramic body.

[0161] By providing a convex heating surface along one or both of the first and second transverse directions, it may be possible to help avoid or minimize the recirculation of the airflow adjacent to the heater assembly. In particular, the convex heating surface may help avoid or minimize the recirculation of the airflow adjacent to the central region of the heater assembly. This may reduce the level of turbulence in the airflow adjacent to the heater assembly. As described above, by reducing the level of turbulence in the airflow adjacent to the heater assembly, the entrainment of vapor from the aerosol-forming substrate into the airflow may be improved. This may improve the quality of the aerosols generated by the aerosol generation system.

[0162] By improving the entrainment of vapor into the airflow passing through the aerosol generation system, it may be possible to avoid or reduce the condensation of vapor into large droplets of liquid aerosol-forming substrate. This may help to avoid an unpleasant and undesirable user experience.

[0163] By improving the entrainment of vapor into the airflow passing through the aerosol generating system, condensation of vapor on the internal surface of the aerosol generating system may be avoided or reduced. This may help avoid or minimize damage to the aerosol generating system and enable the aerosol generating system to function optimally.

[0164] The heating surface of the porous material may be convex in a single transverse direction.

[0165] The heating surface of the porous material may be convex in both the first transverse direction and the second transverse direction.

[0166] The heating surface of the porous material may be convex in one or both of the first and second transverse directions, based on the configuration of the heater assembly with respect to one or more airflow paths in the aerosol generation system. The heater assembly may be configured to minimize the level of turbulence in the airflow adjacent to the heater assembly. For example, it may be advantageous for the heater assembly to be positioned within the aerosol generation system such that the air drawn into the aerosol generation system follows a curved path along at least a portion of the curved surface of the heater assembly.

[0167] The heating element may be convex in one or both of the first and second transverse directions.

[0168] The curvature of the heating element in the first transverse direction may be directly the same as the curvature of the heating surface of the porous body in the first transverse direction. The curvature of the heating element in the second transverse direction may be substantially the same as the curvature of the heating surface of the porous body in the second transverse direction. The curvature of the heating element in both the first and second transverse directions may be substantially the same as the curvature of the heating surface of the porous body in both the first and second transverse directions, respectively.

[0169] The heater assembly may include an insulating layer. The insulating layer may have a lower thermal conductivity than the porous material. The insulating layer may be deposited between the porous material and the heating element. The insulating layer may be in contact with both the porous material and the heating element. The insulating layer may be configured to reduce heat transfer from the heating element to the porous material.

[0170] Advantageously, by providing an insulating layer between the porous body and the heating element, heat loss from the heating element to the porous body and further to the liquid within the porous body is reduced. This provides a more efficient heater assembly that can increase the amount and number of times the device can be used by the user before the device power source, such as a battery, is depleted. The inventors estimate that in known devices, about one-third of the energy from the heating element is lost by conduction within the porous body and by conduction within the liquid within the porous body. The remaining two-thirds are used to generate aerosols by heating the liquid aerosol-forming substrate. In the arrangement described herein, these energy losses are reduced. Specifically, the insulating layer reduces heat propagation or conduction from the heating element to or through the porous body. This reduction in conduction allows heat to be concentrated on the heating surface of the porous body, thereby minimizing heat dissipation and increasing the heating efficiency of the heater assembly.

[0171] The insulating layer may include an insulating material. The insulating material may have a lower thermal conductivity than the porous material. The insulating material may also have a higher porosity than the porous material. This has the advantage of providing an insulating layer that is particularly effective in reducing energy loss while facilitating manufacturing.

[0172] The insulating layer may include a material having a thermal conductivity of less than 40 watts / meter Kelvin. This has the advantage of providing an effective insulating layer in reducing energy loss through the porous material. The insulating layer may include a material having a thermal conductivity of less than 10 watts / meter Kelvin. This has the advantage of providing a particularly effective insulating layer in reducing energy loss through the porous material.

[0173] The insulating layer may extend throughout the space between the porous material and the heat-generating element. This has the advantage of more effectively creating a barrier between the heat-generating element and the porous material, which is particularly effective in reducing energy loss through the porous material.

[0174] The insulating layer may contain one or more of the following: alumina, zirconia, magnesium oxide-containing zirconia, glass ceramic, quartz, or porous polymer. The porous polymer may be polyimide.

[0175] The insulating layer may contain alumina having a thermal conductivity of 20 watts / meter Kelvin to 40 watts / meter Kelvin. The insulating layer may also contain materials having a thermal conductivity of less than 10 watts / meter Kelvin, such as magnesium oxide-containing zirconia, magnesium oxide-free zirconia, glass ceramics, and quartz. The use of alumina, magnesium oxide-containing zirconia, magnesium oxide-free zirconia, glass ceramics, and quartz is advantageous because these materials are suitable for manufacturing processes involving sintering, and therefore heater assemblies having an insulating layer made of one of these materials can be manufactured more easily.

[0176] The insulation layer may have a thickness of 0.1 mm to 2 mm. An insulation layer with such a thickness is particularly suitable for reducing energy loss from the heat-generating element to the porous body. Preferably, the insulation layer has a thickness of 0.5 mm to 1.5 mm. An insulation layer with such a thickness is even more suitable for reducing energy loss from the heat-generating element to the porous body.

[0177] The average pore size of the porous material may differ between the liquid absorption surface and the heating surface.

[0178] Providing a porous body that includes a change in pore size between the liquid absorption surface and the heating surface is advantageous because it can help control the transport of the liquid aerosol-forming substrate from the storage portion to the heating element. Specifically, by changing the pore size between the liquid absorption surface and the heating surface, the porous body may be able to consistently supply the aerosol-forming substrate to the heating surface. This can advantageously avoid undesirable "dry heating". In addition, the porous body of the present invention can advantageously prevent leakage of the liquid aerosol-forming substrate from the heating surface of the porous body.

[0179] The average pore size of the porous material may vary between the liquid absorption surface and the heating surface. The average pore size may change from relatively large pores on the liquid absorption surface to relatively small pores on the heating surface.

[0180] By providing a porous body having a larger average pore diameter at the liquid absorption end and a smaller average pore diameter at the heating end, the efficient transfer of the liquid aerosol-forming substrate from the liquid absorption end to the heating end of the porous body can be facilitated without allowing leakage. In particular, the inventors of the present invention have confirmed that the liquid aerosol-forming substrate is transferred from the liquid absorption end to the heating end of the porous body by capillary action. The speed at which the liquid aerosol-forming substrate moves through the porous body depends on many factors, including, but are not limited, the shape of the pores, the surface tension between the liquid aerosol-forming substrate and the porous body, the viscosity of the liquid aerosol-forming substrate, and the surface tension of the liquid aerosol-forming substrate. The inventors of the present invention have confirmed the need to balance these factors in order to provide efficient transfer of the liquid aerosol-forming substrate to the heating surface of the porous body while preventing leakage of the liquid aerosol-forming substrate.

[0181] Firstly, in order to provide efficient capillary flow of liquid through a porous material, the capillary pressure must overcome the viscous drag pressure. Secondly, in order to prevent leakage, the inertial force must not overcome the capillary pressure. These two requirements are met by providing a porous material that has larger pores at the liquid absorption end and smaller pores at the heating end.

[0182] In particular, the inventors of this invention noticed that the viscosity of the liquid aerosol-forming substrate changes with temperature. Specifically, the viscosity of the liquid aerosol-forming substrate decreases as its temperature rises. As a result, the viscosity of the liquid aerosol-forming substrate decreases as it moves through the porous material from the liquid absorption surface to the heating surface. As the liquid aerosol-forming substrate is transported through the porous material by capillary forces, these capillary forces must overcome the viscous resistance of the liquid. Viscous resistance decreases as viscosity decreases. As a result, the capillary forces required to move the liquid aerosol-forming substrate can be reduced toward the heating surface of the porous material while maintaining the same flow rate. Consequently, the average pore size of the porous material can be reduced toward the heating surface without reducing the flow of the liquid aerosol-forming substrate through the porous material.

[0183] The heating element may comprise multiple tracks or track sections arranged electrically in parallel. The resistance of the heating element at room temperature may be 0.5 ohms to 1.5 ohms, preferably 0.7 ohms to 1.3 ohms, and more preferably 1 ohm. The resistance of the heating element may match the requirements of the control electronic equipment.

[0184] At least two electrically parallel heating tracks may have similar resistances to each other, or they may have the same resistance to each other. Preferably, all electrically parallel heating tracks have similar or identical resistances to each other. Electrically parallel heating tracks may have different resistances, which is particularly beneficial in heater assemblies where it is advantageous for each zone of the heating element to operate at different power levels. This may be, for example, to compensate for higher heat loss in the outer portion of the heating element. Thus, heating tracks on or on the outer portion of the heating element may be designed to have lower resistances (and thus generate more heat) compared to the central heating track of the heating element.

[0185] The heating element may have multiple tracks or track sections. The multiple tracks or track sections may be electrically arranged in parallel. By being electrically arranged in parallel, the current flow is divided into separate parallel channels, which then merge again.

[0186] The heating element may include a first connection pad and a second connection pad. One of the first and second connection pads (or both) may be configured to allow connection to an external circuit. Openings or multiple openings in the heating element may separate each track or each track portion. The heating element may include at least one branching section where the current is divided from the first connection pad to each track portion. The track portions define electrically parallel paths. The heating element may include a converging section where the current merges from each track portion defining each electrically parallel path to the second connection pad.

[0187] With respect to electrically parallel-arranged tracks or track sections, various different arrangements are possible. The heating element may comprise two, three, four, or more track sections, each defining an electrically parallel path.

[0188] Advantageously, by providing electrically parallel tracks or track sections, even if one track section is defective, the current can be redistributed and still flow through the heating element; that is, the electrical connection between the first and second connection pads is not broken. In contrast, in a simple meandering heater that defines a single electrical path between the first and second connection pads, if part of the meandering heating element is damaged or defective, it causes an increase in local resistance, leading to increased power dissipation, and ultimately, continued increase in resistance that results in failure.

[0189] The inventors have also confirmed that electrically parallel tracks or track sections have a surprising additional advantage. In this arrangement, even if one track section fails, the heating element will still operate, and for an initial transient period, the failure of one track or track section will result in a greater energy density on the remaining tracks or track sections, allowing it to operate in a favorable manner. In such a case, the throughput of the aerosol-forming substrate is improved because the same power is supplied but only a smaller area is operating. Such failure increases the current in the undamaged tracks or track sections, which can ultimately affect the user experience. This can be mitigated by a mechanism that warns the user of the possibility of the heater assembly falling below optimal performance in the future. Electrically parallel tracks have the advantage of increasing the number of fume extractions before the heater completely fails, potentially extending the heater's lifespan to the end of the device's life.

[0190] The heating element may comprise multiple tracks or track sections that define a path having at least one bend. The inner edges of the bends may be curved.

[0191] The curvature of the inner edge of a bend has the advantage of guiding the current in a more evenly distributed manner around at least one bend. This reduces current concentration and limits the occurrence of hot spots.

[0192] The heating element may have multiple tracks or track sections having an electrical resistivity gradient perpendicular to the current flow at a corner or at multiple corners, so that the electrical resistivity is higher on the inside of the corner and lower on the outside of the corner. Such a gradient is beneficial in counteracting localized high current densities and in reducing the occurrence of hot spots.

[0193] The aerosol generation system may comprise an aerosol generator and a cartridge. The cartridge may be detachably coupled to the aerosol generator. The cartridge may comprise any of the exemplary heater assemblies described above. The cartridge may comprise a liquid storage portion, i.e., a liquid storage section, configured to hold a liquid aerosol-forming substrate. The liquid storage portion may be located on the side opposite to the heating surface of the heater assembly. Alternatively, the aerosol generator may comprise any of the exemplary heater assemblies described above.

[0194] As used herein, the term "aerosol-forming substrate" refers to a substrate capable of releasing volatile compounds that can form aerosols. The volatile compounds may be released by heating the liquid aerosol-forming substrate.

[0195] The aerosol-forming substrate may be liquid at room temperature. The aerosol-forming substrate may comprise both a liquid component and a solid component. The liquid aerosol-forming substrate may contain nicotine. The nicotine-containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may contain plant-derived materials. The liquid aerosol-forming substrate may contain tobacco. The liquid aerosol-forming substrate may contain tobacco-containing materials that contain volatile tobacco-flavored compounds released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may contain homogenized tobacco materials. The liquid aerosol-forming substrate may contain non-tobacco-containing materials. The liquid aerosol-forming substrate may contain homogenized plant-derived materials.

[0196] The liquid aerosol-forming substrate may contain one or more aerosol-forming compounds. The aerosol-forming compounds are any suitable known compounds or mixtures of compounds that facilitate the formation of a high-density, stable aerosol during use and are substantially resistant to thermal decomposition at the system's operating temperature. Examples of suitable aerosol-forming compounds include glycerin and propylene glycol. Suitable aerosol-forming compounds are well known in the art and include, but are not limited to, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, glycerin), esters of polyhydric alcohols (e.g., glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (e.g., dimethyl dodecanediol, dimethyl tetradecanediol). The liquid aerosol-forming substrate may also contain water, a solvent, ethanol, plant extracts, and natural or artificial flavorings.

[0197] The liquid aerosol-forming substrate may contain nicotine and at least one aerosol-forming agent. The aerosol-forming agent may be glycerin or propylene glycol. The aerosol-forming agent may contain both glycerin and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of about 0.5% to about 10%, for example, about 2%.

[0198] The airflow path may pass through the liquid storage section. For example, the liquid storage section may have an annular cross-section defining an internal passage or aerosol channel, and the airflow path may extend through the internal passage or aerosol channel of the liquid storage section.

[0199] The cartridge may include a cartridge housing. The cartridge housing may be formed from a durable material. The cartridge housing may be formed from a liquid-impermeable material. The cartridge housing may be formed from a moldable plastic material such as polypropylene (PP) or polyethylene terephthalate (PET), or from a copolymer such as Tritan® made from three monomers, namely dimethyl terephthalate (DMT), cyclohexanedimethanol (CHDM), and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). The cartridge housing of the cartridge may define a liquid storage portion, i.e., a part of the liquid storage section. The cartridge housing may define the liquid storage section. The cartridge housing and the liquid storage section may be formed integrally. Alternatively, the liquid storage section may be formed separately from the outer housing or disposed within the outer housing.

[0200] The aerosol generator may include a power supply for supplying power to the heater assembly. The aerosol generator may also include a control circuit for controlling the power supply from the power supply to the heater assembly. The cartridge may be detachably coupled to the aerosol generator.

[0201] The aerosol generator may include a housing. The housing may be elongated. The housing may contain any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials containing one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and not brittle.

[0202] The aerosol generator housing may define a cavity for receiving a portion of the cartridge. The aerosol generator may have a connecting terminal configured to connect the aerosol generator to the cartridge. The connecting terminal may include a cavity for receiving the cartridge.

[0203] The power source may be any suitable power source. Preferably, the power source is a DC power source. The power source may be a battery. The battery may be a lithium-based battery, for example, a lithium cobalt battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium polymer battery. The battery may be a nickel-metal hydride battery or a nickel-cadmium battery. The power source may be another form of charge storage device, such as a capacitor. The power source may be rechargeable and may be configured for numerous charge and discharge cycles. The power source may have a capacity that allows for sufficient energy storage for one or more user experiences of the aerosol generating system. For example, the power source may have a capacity that allows for continuous aerosol generation for about six minutes, corresponding to the typical time it takes to smoke one conventional cigarette, or for a time that is a multiple of six minutes. In another example, the power source may have a capacity that allows for a predetermined number of smoking sessions or for intermittent startup of the aerosol generating system.

[0204] The control circuit may include any suitable controller or electrical component. The controller may include memory. Information for carrying out the method described above may be stored in memory. The control circuit may include a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), or other electronic circuit capable of providing control. The control circuit may be configured to supply power to the heating element continuously after the device is started, or to supply power intermittently, such as with each smoke extraction. Power may be supplied to the heating element in the form of current pulses, for example by pulse width modulation (PWM).

[0205] Each feature described in relation to one of the above examples may be equally applicable to other examples of this disclosure. [Examples]

[0206] The present invention is defined in the claims. However, a non-exclusive list of non-limiting embodiments is provided below. Any one or more features of each feature in these embodiments may be combined with any one or more features of other embodiments, other forms, or other aspects described herein.

[0207] Example 1: A heater assembly comprising a heating element for vaporizing a liquid aerosol-forming substrate and a porous body for transporting the liquid aerosol-forming substrate to the heating element. Example 2: The porous body is the heater assembly described in Example 1, which includes a liquid absorption surface and a heating surface. Example 3: The heating element is a heater assembly as described in Example 1 or Example 2, which is placed on the heating surface of a porous body. Example 4: The heating element is a heater assembly described in any of Examples 1 to 3, which is fluid permeable. Example 5: The heater assembly according to any one of Examples 1 to 4, wherein the porous body comprises at least one airflow guide for guiding airflow toward a heating element. Example 6: The heating element is porous, as described in any of Examples 1 to 5. Example 7: The heating element is the heater assembly described in Example 6, having a porosity of 20% to 80%. Example 8: The heating element is a heater assembly according to Example 6 or Example 7, comprising a porous layer of conductive material. Example 9: The heating element is the heater assembly described in Example 8, which includes a porous metal film. Example 10: The heating element is the heater assembly described in Example 8, which includes a metal foam. Example 11: A heater assembly according to any of Examples 1 to 10, wherein the heating element and the porous body are integrally formed. Example 12: The heating element is a heater assembly according to any one of Examples 1 to 11, including a doped portion of a porous material. Example 13: A heater assembly according to any of Examples 1 to 10, wherein the porous body and the heating element are formed as two separate components assembled together. Example 14: The heating element is bonded to the heating surface of the porous body, as described in Example 13. Example 15: The heating element is a heater assembly as described in any of Examples 1 to 14, having a tapered cross-sectional shape. Example 16: The heater assembly described in Example 15 has a tapered shape in the direction from the liquid absorption surface to the heating surface. Example 17: The heater assembly according to Example 15 or Example 16, wherein the liquid absorption surface of the porous material has a different area from the heating surface of the porous material. Example 18: The heater assembly described in Example 17, wherein the heating surface area of ​​the porous material is smaller than the liquid absorption surface area of ​​the porous material. Example 19: The heater assembly described in Example 17, wherein the heating surface area of ​​the porous material is larger than the liquid absorption surface area of ​​the porous material. Example 20: The heating surface of the porous body is convex in one or both of the first and second transverse directions, and the first transverse direction is perpendicular to the second transverse direction, as described in any of Examples 1 to 19. Example 21: The heater assembly according to any one of Examples 1 to 20, further comprising an insulating layer configured to reduce heat transfer from the heating element to the porous body. Example 22: The heater assembly described in Example 21, wherein the insulating layer has a lower thermal conductivity than the porous material. Example 23: The insulating layer is deposited between the porous body and the heating element in the heater assembly described in Example 21 or Example 22. Example 24: The heater assembly according to Example 21 or Example 22, wherein the insulating layer is in contact with the porous body and the heating element, respectively. Example 25: The average pore size of the porous material varies between the liquid absorption surface and the heating surface, as described in any of Examples 1 to 24. Example 26: The heater assembly described in Example 25 has an average pore size that changes from relatively large pores on the liquid absorption surface to relatively small pores on the heating surface. Example 27: The heating element is a heater assembly according to any one of Examples 1 to 26, comprising multiple tracks or track sections electrically arranged in parallel. Example 28: A heater assembly according to any of Examples 1 to 27, wherein the heating element includes a plurality of tracks or track portions defining a path having at least one bend, and the inner edge of the bend is curved. Example 29: An aerosol generating system comprising a heater assembly described in any one of Examples 1 to 28. Example 30: The aerosol generating system according to Example 29, wherein when in use, steam is released from the heater assembly in the average steam discharge direction. Example 31: The aerosol generating system according to Example 29 or Example 30, further comprising an air intake and an aerosol outlet, wherein the air intake is in fluid communication with the aerosol outlet, thereby defining an airflow path through the aerosol generating system. Example 32: The aerosol generating system according to Example 31, wherein the heater assembly is arranged in fluid communication with the airflow path so that air flows through the heater assembly in the mean airflow direction. Example 33: The aerosol generating system according to Example 32, wherein the heater assembly and airflow path are arranged such that the angle between the mean vapor discharge direction and the mean airflow direction is less than 135 degrees. Example 34: The aerosol generating system according to any one of Examples 30 to 33, wherein the average vapor emission direction is substantially perpendicular to the heating surface. Example 35: The aerosol generating system according to Example 33 or Example 34, wherein the heater assembly and airflow path are arranged such that the angle between the average vapor discharge direction and the average airflow direction is approximately 90 degrees. Example 36: The aerosol generating system according to Example 33 or Example 34, wherein the heater assembly and airflow path are arranged such that the angle between the mean vapor discharge direction and the mean airflow direction is less than 90 degrees. Example 37: The aerosol generating system according to Example 36, wherein the heater assembly and airflow path are arranged such that the mean vapor discharge direction and the mean airflow direction are substantially the same. Example 38: The aerosol generating system according to any of Examples 31 to 37, wherein the air intake is located distal to the heater assembly. Example 39: The aerosol generating system according to any one of Examples 31 to 38, wherein the cross-sectional area of ​​the airflow path in the heater assembly region is configured such that the airflow velocity is 0.1 meters / second to 2 meters / second during use. Example 40: A method for manufacturing a heater assembly for an aerosol generating system, comprising forming a porous ceramic body for transporting a liquid aerosol forming substrate, wherein the porous ceramic body has a liquid absorption surface and a heating surface; and providing a heating element for vaporizing the liquid aerosol forming substrate, wherein the heating element is positioned on the heating surface of the porous ceramic body. Example 41: The heating element is bonded to the heating surface of the porous body, as described in Example 40. Example 42: The method according to Example 40, wherein the step of providing a heating element includes depositing a porous layer of conductive material on the heating surface of a porous ceramic body. Example 43: The heating element is deposited or patterned by a thick-film technique selected from one or more of the following: screen printing, inkjet printing, aerosol jet printing, and laser direct structuring (LDS), as described in Example 42. Example 44: The heating element is deposited or patterned by a thin-film technique selected from one or more physical vapor deposition (PVD) techniques such as vapor deposition or sputtering, and chemical vapor deposition (CVD), as described in Example 42. Example 45: The method according to Example 40, wherein the heating element and the porous body are formed integrally. Example 46: The method according to Example 45, wherein the step of providing the heating element includes doping a portion of a porous ceramic body to form a heating portion for vaporizing a liquid aerosol generating substrate.

Claims

1. an aerosol generation system, A heat-generating element for vaporizing a liquid aerosol-forming substrate, and The heating element comprises a porous body for transporting the liquid aerosol forming substrate, wherein the porous body includes a liquid absorption surface and a heating surface, and the heating element includes a heater assembly comprising a porous body disposed on the heating surface of the porous body. The heating element is fluid-permeable so that when in use, steam is released from the heater assembly in the average steam discharge direction. The aerosol generating system further comprises an air intake and an aerosol outlet, and the air intake is in fluid communication with the aerosol outlet, thereby defining the airflow path through the aerosol generating system. An aerosol generating system in which the heater assembly is arranged in fluid communication with the airflow path such that air flows through the heater assembly in the mean airflow direction, and the heater assembly and the airflow path are arranged such that the angle between the mean vapor discharge direction and the mean airflow direction is less than 90 degrees.

2. The aerosol generating system according to claim 1, wherein the average vapor discharge direction is substantially perpendicular to the heating surface.

3. The aerosol generating system according to claim 1 or 2, wherein the heater assembly and the airflow path are arranged such that the average vapor discharge direction and the average airflow direction are substantially the same.

4. The aerosol generating system according to any one of claims 1 to 3, wherein the porous body comprises at least one airflow guide for guiding the airflow toward the heating element.

5. The aerosol generating system according to any one of claims 1 to 4, wherein the air intake is located distal to the heater assembly.

6. The aerosol generating system according to any one of claims 1 to 5, wherein the cross-sectional area of ​​the airflow path in the region of the heater assembly is 9.15 square millimeters to 183 square millimeters.

7. The aerosol generating system according to any one of claims 1 to 6, wherein the heating element includes a porous layer of a conductive material.

8. The aerosol generating system according to any one of claims 1 to 7, wherein the heating element and the porous body are integrally formed.

9. The aerosol generating system according to any one of claims 1 to 7, wherein the heating element is bonded to the heating surface of the porous body.

10. The aerosol generating system according to any one of claims 1 to 9, wherein the heating element has a tapered cross-sectional shape.

11. The aerosol generating system according to any one of claims 1 to 10, wherein the heating surface of the porous body is convex in one or both of the first transverse direction and the second transverse direction, and the first transverse direction is perpendicular to the second transverse direction.

12. The aerosol generating system according to any one of claims 1 to 11, wherein the heater assembly further includes an insulating layer having a lower thermal conductivity than the porous body, the insulating layer is deposited between the porous body and the heating element and is in contact with the porous body and the heating element respectively, and the insulating layer is configured to reduce heat transfer from the heating element to the porous body.

13. The aerosol generating system according to any one of claims 1 to 12, wherein the heating element includes a doped portion of the porous body.

14. The aerosol generating system according to any one of claims 1 to 13, wherein the average pore diameter of the porous body varies between the liquid absorption surface and the heating surface.

15. The aerosol generating system according to any one of claims 1 to 14, wherein the heating element includes a plurality of tracks or track portions arranged electrically in parallel.

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