Aerosol generation system and method for guiding airflow inside an electrically heated aerosol generation system

Abstract

To provide an electrically heated aerosol-generating system such as an electrically heated smoking system, and especially a method for guiding an airflow inside the system.SOLUTION: An aerosol-generating system 8 comprises a liquid storage portion including a container holding a liquid aerosol-forming substrate 41 and defining an opening, and a heater assembly 30 which extends across the opening along a transverse plane. The heater assembly includes at least one electrically operated heating element, and a first channel defining a first flow route which brings ambient air into impingement against the heater assembly. In an embodiment, a portion of the first channel is arranged orthogonally to the transverse plane such that the at least a portion of the first channel directs ambient air from outside the system to impinge perpendicularly onto a surface portion of the heating element before conveying the ambient air to a downstream end.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to an electrically heated aerosol generation system such as an electrically heated smoking system, and a method for guiding an air flow inside such a system.

Background Art

[0002] Some aerosol generation systems can include a battery and a control electronic circuit, a cartridge containing an aerosol-forming substrate source, and an electrically operated vaporizer. The substance is vaporized from the aerosol-forming substrate, for example, by a heater. During inhalation (e.g., smoking) by the user at the mouth-side end, the air flow passes through the heater, mixes with the vaporized liquid, and guides it through the mouthpiece to the mouth-side end of the mouthpiece.

Summary of the Invention

Problems to be Solved by the Invention

[0003] It is desirable to manipulate the air flow so that as much of the liquid vaporized by the heater as possible is conveyed away from the heating zone for each inhalation during smoking. It is further desirable to manipulate the flow to minimize the formation of droplets outside the desired inhalable range.

Means for Solving the Problems

[0004] According to a first aspect, an electrically heated smoking system for generating an aerosol is provided. The smoking system to be heated utilizes a heater positioned relative to an airflow system having one or more channels for drawing in downstream air and ambient air. Each of the one or more channels defines a respective flow path. The first flow path defined by the first channel is oriented such that air from outside the system impinges on one or more electrical heating elements of the heater before carrying the ambient air to the downstream end. The air conveyed along each first flow path may be oriented towards the heater as un-preheated ambient air, or may be subjected to a preheating step before impinging on and along the heater.

[0005] In some embodiments, the first flow path causes the air to first impinge along a path that is substantially orthogonal to the plane in which the electrical heating element(s) of the heater are disposed. Such an arrangement is advantageous because it has been found to promote efficient mixing of the vapor when the angle of impingement is perpendicular and oriented towards the geometric center of the heater. When multiple channels are used, the respective flows may merge before or at some point along a common orthogonal path. Alternatively, one or more flows may be made to impinge on the heater assembly at any angle, such that the flows impinge on and along a common plane passing through one or more heating element(s).

[0006] The vapor within the heater zone is collected by the air flowing within the one or more channels and conveyed to the downstream end of the airflow system. When the vapor condenses within the flowing air, droplets are formed, thereby generating an aerosol. It has been found that ambient airflow impinging at a 90-degree angle on the heating element efficiently and effectively mixes the vapor so that it can be guided to the end of the "mouth" downstream of the system. The greater the ambient airflow hitting the heating element, the greater the efficiency of vapor mixing and discharge. In particular, when the ambient air impinges at an angle orthogonal to its geometric center on the surface of the heating assembly, a homogeneous airflow across the heating element may be provided radially outwards.

[0007] The volume of ambient air passing through the first and any additional channels and impinging at a right angle to the heating element(s) may vary, for example, to be adapted to the type of heating element applied or the amount of vaporized liquid available. For example, the volume of ambient air impinging on the heating element may be adapted to the total area effectively heated by the heating element.

[0008] In embodiments, the heated vapor-containing air leaving the heater zone passes along a transverse cooling zone adjacent where the aerosol-forming substrate is stored in the cartridge. In this zone, the temperature of the surface of the cartridge is lower than the temperature of the vapor-containing air, so such a vicinity has a significant cooling effect. This effect is particularly pronounced when air passes through narrow channels sized and arranged to maximize the flow interaction within the surface of the cartridge. The resulting rapid cooling causes supersaturation of the air with the vaporized liquid, which promotes the formation of smaller aerosol droplets as a result. In some embodiments, it is preferred to maintain the droplet size in the inhalable range of 0.5 to 1 micrometer during vapor condensation.

[0009] In some embodiments, a sharp bend (e.g., about 90 degrees) in the aerosol flow around a portion of the cartridge housing containing the liquid substrate performs a complementary droplet filtering function, and droplets beyond the inhalable range condense at the corner(s) of the flow path so as not to be delivered to the downstream end.

[0010] In principle, whenever the term "about" is used throughout this specification in relation to a particular value, it is understood that the value following the term "about" need not have that particular value precisely and exactly for technical considerations. However, the term "about" used in relation to a particular value is always understood to include and be inclusive of the particular value following the term "about".

[0011] Regarding the direction and position of the heater with respect to the opening in the container containing the liquid that generates the aerosol, the term "transverse" is intended to mean an arrangement in which one or more heating elements that pass through a common plane (e.g., the plane transects the container opening) are positioned over or across at least a portion of the opening. In some embodiments, for example, the heater may completely cover the opening of the container, while in other embodiments, the heater may only partially cover the opening of the container. In yet another embodiment, the heater may be positioned within the opening so as to extend across the entire opening on all sides, while in yet another embodiment, the heater may be positioned to extend across a first pair of opposite portions of the opening and not across a second pair of opposite portions of the opening.

[0012] As used herein, the terms "upstream" and "downstream" are used from the perspective of the direction of the airflow within the system. The upstream and downstream ends of the system are defined with respect to the airflow when the user inhales at the proximal or mouth-side end of the aerosol-generating smoking article. Air is drawn into the system at the upstream end, passes through the system downstream, and exits the system at the proximal or downstream end. As used herein, the terms "proximal" and "distal" mean the position of an element with respect to the direction towards or away from the consumer. Therefore, the proximal end of the mouthpiece of the aerosol-generating system corresponds to the mouth-side end of the mouthpiece. The distal opening of the cartridge housing therefore corresponds to the position of the opening disposed within the cartridge housing that faces away from the consumer.

[0013] A heater used in a smoking system consistent with embodiments of the present disclosure may be, for example, a fluid-permeable heating assembly comprising one or more conductive heating elements. The one or more conductive heating elements are sized to generate heat when an electric current is applied thereto and are arranged to generate heat. The fluid-permeable heating assembly is suitable for the vaporization of different types of cartridge liquids. For example, as a liquid aerosol-forming substrate, the cartridge may include a liquid or a carrier material containing a liquid (such as a capillary material, etc.). Such carrier materials and capillary materials preferably actively carry the liquid and are directed within the cartridge to carry the liquid to the heating element. In an embodiment, the one or more conductive heating elements, which are heat-generating filaments, are arranged near a liquid or a capillary material containing a liquid such that the heat generated by the heating element vaporizes the liquid. The filament and the aerosol-forming substrate are preferably arranged such that the liquid can flow into the gaps of the filament arrangement by capillary action. The filament arrangement may also be in physical contact with the capillary material.

[0014] In an embodiment, the fluid-permeable heating assembly comprises one or more heating elements through which a common plane passes such that the heater is in a substantially flat orientation. Such a heating element may be, for example, a flat coil embedded in a porous ceramic or a mesh heater, and the mesh or another filament arrangement is arranged across the opening of the heater. The fluid-permeable heating assembly may comprise, for example, a conductive mesh or coil pattern printed on a heat-resistant support component. The support component may be a ceramic, polyetheretherketone (PEEK), or other heat-resistant ceramic and polymer that does not thermally decompose and does not release volatile elements at a temperature below 200 °C, preferably below 150 °C.

[0015] The heater vaporizes liquid from a cartridge or cartridge housing containing an aerosol-forming substrate. The aerosol-forming substrate is a substrate having the ability to release volatile compounds capable of forming an aerosol. The volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate may include plant-derived materials. The aerosol-forming substrate may include tobacco. The aerosol-forming substrate may include a tobacco-containing material containing volatile tobacco flavor compounds released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may include a non-tobacco-containing material. The aerosol-forming substrate may include a homogenized plant-derived material. The aerosol-forming substrate may include a homogenized tobacco material. The aerosol-forming substrate may include at least one aerosol former. The aerosol former is any suitable known compound or mixture of compounds that facilitates the formation of a dense and stable aerosol in use and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerol), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Preferred aerosol formers are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerol (most preferred)). The aerosol-forming substrate may include other additives and components (such as flavorants).

[0016] The aerosol-forming substrate may be carried to the heater(s) via a capillary material that contacts or is adjacent to the heater(s). The capillary material may have a fibrous or spongy structure. The capillary material preferably comprises a bundle of capillaries. For example, the capillary material may comprise a plurality of fibers or threads, or other fine tubes. The fibers or threads may generally be aligned to carry liquid to the heater. Alternatively, the capillary material may comprise a sponge-like or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which liquid can be transported by capillary action. The capillary material can comprise any suitable material or combination of materials. Examples of suitable materials include sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metal or plastic materials, for example fibrous materials made of spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics). The capillary material may have any suitable capillary and porosity to be used with different liquid physical properties. The liquid has physical properties including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure that allow it to be transported through the capillary device by capillary action.

[0017] The capillary material may contact the conductive filament of the heater. The capillary material may extend into the gaps between the filaments. The heater may draw the liquid aerosol-forming substrate into the gaps by capillary action. The capillary material may contact the conductive filament substantially over the entire length of the opening of the heater.

[0018] The heating element(s) can be provided within a heating assembly that includes a support element. The heating assembly can include two or more different capillary materials, where the first capillary material in contact with the heating element has a higher thermal decomposition temperature, and the second capillary material in contact with the first capillary material but not in contact with the heating element has a lower thermal decomposition temperature. The first capillary material effectively serves as a spacer that separates the heating element from the second capillary material so that the second capillary material is not exposed to a temperature above its thermal decomposition temperature. As used herein, "thermal decomposition temperature" means the temperature at which a material begins to decompose and loses mass by generating gaseous by-products. The second capillary material can advantageously occupy a larger volume than the first capillary material, but can also hold more aerosol-forming substrate than the first capillary material. The second capillary material can have better wicking performance than the first capillary material. The second capillary material can be less expensive than the first capillary material or can have a high filling capacity. The second capillary material can be polypropylene.

[0019] The flow path(s) can be selected to achieve a desired result, for example, such that a predetermined air volume passes through one or more channels and impinges on the heater surface(s). For example, the length or diameter of the channels can be varied to achieve, for example, a predetermined draw resistance (RTD). The flow path(s) can be selected according to the setup of the aerosol-generating smoking system and also according to the arrangement and characteristics of the individual components of the smoking system. For example, the aerosol can be generated at the proximal or distal end of a cartridge housing containing the aerosol-forming substrate. Depending on the orientation of the cartridge within the aerosol-generating smoking system, the open end of the cartridge housing is arranged facing the mouthpiece or in a direction away from the mouthpiece. Thus, the heating element for heating the aerosol-forming substrate is arranged at the proximal or distal end of the housing. It is preferred that the liquid is vaporized at the open distal end of the mouthpiece and the heating element is arranged between the cartridge and the mouthpiece.

[0020] In some embodiments, one or more heating elements are disposed at the open proximal end of the cartridge housing, for example, arranged to cover the proximal end of the cartridge (upper version). In such embodiments, the first flow path and the first channel may be entirely disposed within the mouthpiece of the smoking system, the first air inlet is disposed within the sidewall of the mouthpiece, and one or some of the outlets of the first channel are disposed at the proximal end or the mouth-side end of the mouthpiece. Optionally, additional flow paths and channels are defined within the mouthpiece. The first and any additional channels are arranged depending on the location of the heating element(s) of the smoking system. For example, in an embodiment where the heating element is disposed at the open proximal end of the cartridge housing, for example, to cover the proximal end of the cartridge (upper version), the channel(s) may be entirely disposed within the mouthpiece.

[0021] In an alternative embodiment where one or more heating elements are disposed at the open distal end of the cartridge housing, the flow path(s) typically starts at a further distal location within the smoking system, for example, in the distal end region of the cartridge housing. For this purpose, the air inlet(s) and the first portion of each channel may be disposed within the main section of the smoking system to define a first channel portion in fluid communication with a corresponding channel portion defined within the mouthpiece. Next, ambient air is directed into the system, passes through the heating element at the distal end of the cartridge, and mixes with the vapor generated by heating the aerosol-forming substrate within the cartridge. Next, the aerosol containing air may be guided along the cartridge between the cartridge housing and the main housing towards the downstream end of the system, where it is mixed with the ambient air from the first flow path (either before or upon reaching the downstream end).

[0022] A single channel may branch into several channel portions downstream of the heating element(s), and several channel portions upstream of the heating element(s) may merge into a single channel before colliding orthogonally with respect to the geometric center of the heater. Further, the first channel may consist of several first partial channels, and the second channel may consist of several second partial channels.

[0023] The flow path may provide numerous variations that supply ambient air to the heating element and convey the aerosol away from the heating element to the downstream end of the system. For example, the supply of ambient air in the radial direction is preferably combined with a large central extraction. The supply of ambient air in the center is preferably combined with a radial air distribution across the entire surface of the heating element so that the air containing the aerosol is carried from the periphery to the downstream end. In such an embodiment, the flow path is integrated to direct ambient air to the heating element, for example, at a right angle to the heating element, preferably oriented to collide with the center of the heating element.

[0024] An air flow oriented at a right angle to the central portion of the heating element shows an improvement in aerosolization in that there are smaller particle sizes and a greater amount of total particulate matter particles in the aerosol stream when compared to an air flow that collides with the surface at an angle greater than 0 degrees and less than 90 degrees. This is due to a lower level of air flow vortices generated at the heater element and the air flow interface, an improvement in aerosol generation by maximizing the entire heater (e.g., portions other than the central portion of the heater element contribute to the addition or increase of the aerosol), or an increase in the suction effect based on an increase in the amount of air crossing the heating element.

[0025] A method for guiding the air flow in an electrically heated smoking system to generate an aerosol includes directing ambient air from outside the system at a right angle to the heating element and carrying the air containing the heated vapor to promote supersaturation of the vapor generated by heating the liquid.

[0026] The present invention will be further described with respect to embodiments, which will be illustrated by the following charts and diagrams.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9a

Figure 9b

[0028] In FIG. 1, an embodiment of a cartridge 4 and a mouthpiece 1 for an aerosol-generating smoking system is shown. The elongated main housing 5 houses the cartridge together with an aerosol-forming substrate, for example, a tubular container 4 containing a capillary material 41 containing a liquid. The container 4 has an open proximal end 42. The heater 30 is arranged to cover the open proximal end of the container 4. In some embodiments, the heater 30 is a fluid-permeable heater having a substantially flat cross-section. In one embodiment, the heater 30 is a substantially flat mesh arrangement of electrically heated filaments. The filaments or other heating element(s) of the heater 30 may or may not be in physical direct contact with the aerosol-forming substrate 41. The mouthpiece 1 having a substantially tubular elongated body 15 is aligned with the main housing, the container 4, and the heater 30. The elongated body 15 has an open distal end facing the heater 30.

[0029] The embodiment shown in FIG. 1 includes a first channel 10 that defines a first flow path into the mouthpiece 1. The incoming ambient air 20 enters the first flow path via the inlet 100 and proceeds through the flow path defined by the first channel 10. This flow path causes the ambient air to impinge on the center of the heater 30. The impingement preferably occurs at the geometric center of the heater and at an angle of 90 degrees or nearly 90 degrees (i.e., the flow is substantially orthogonal to the plane containing the heating surface(s) of the heater 30). The vaporized liquid generated by the heater 30 is entrained by the air flow 20 as an aerosol and delivered therefrom to the outlet 12 at the proximal or mouth-side end of the mouthpiece 1 so that it is inhaled when the consumer smokes. In some embodiments, a single channel as the first channel 10 may be sufficient alone to draw in a desired amount of ambient air for each puff. In other embodiments, it may be desirable to include two or more inlets and associated channels. For example, a second channel (not shown) may be provided to draw in additional air such that the ambient air flows merge before impinging on the heater 30.

[0030] In the embodiment of FIG. 1, the inlet 100 to the first flow path is an opening or perforation located within the mouthpiece 1, in the distal half of the elongate body 15 of the mouthpiece 1. The first flow path within the upstream second channel portion 101 flows through the elongate body parallel to the perimeter of the elongate body towards the proximal end of the mouthpiece. In the radially inwardly oriented portion 102 of the first channel 10, the first air stream 20 is oriented towards the center of the elongate body, and in the portion 103 disposed at the center of the first channel, the first air stream 20 is oriented towards the heater 30 so as to impinge on the central portion 31 of the heater 30. The first air stream 20 passes over the heater 30 and diffuses radially outwards towards some of the longitudinal ends 104 of the first channel 10. The longitudinal ends 104 are regularly arranged along the perimeter within the elongate body.

[0031] In this embodiment, the flow path and corresponding channels are disposed entirely within the mouthpiece 1 of the aerosol generating system. For example, one or more additional flow paths defined by symmetrically disposed channels may be defined within the mouthpiece such that the flows integrate by the time the ambient air reaches the centrally disposed portion 103.

[0032] FIG. 2 illustrates an embodiment of a cartridge 4 including a heater 30 disposed at the bottom of the cartridge and covering the open distal end 43 of the container 41. In this embodiment, the first inlet 100A is disposed within the main housing 5, and ambient air 20A is directed directly from within the radially inwardly oriented portion 102A of the first channel toward the center of the main housing. Further, the second inlet 100B is disposed within the main housing 5, and ambient air 20B is directed directly from within the second radially inwardly oriented channel 102B toward the center of the main housing 5. The first and second channels are integrated to form a single flow within the portion 103 disposed at the center of the first channel, and the integrated air stream is oriented to impinge perpendicularly onto the heater 30. Next, the air passes through the heater 30 and mixes with the aerosol produced by heating the liquid within the aerosol-forming substrate 41 by the heater 30. The aerosol-containing air enters one of several elongated longitudinally oriented portions 105 of the first channel 10 disposed between and along the inner surfaces of the cartridge 4 and the main housing 5, and after a 90-degree bend, is directed toward the proximal end of the cartridge 4.

[0033] Thus, the aerosol-containing air stream is directed to a single opening 52 disposed at the center within the main housing 5 and is guided to exit therefrom. A mouthpiece (not shown) may be disposed adjacent to and aligned with the main housing. Next, the mouthpiece preferably also has a centrally disposed opening and an end 104 of the first channel 10 for receiving the aerosol-containing air stream and guiding it to a single outlet opening 12 within the proximal end of the mouthpiece 1.

[0034] Figures 3A and 3B illustrate an additional embodiment of a system 8 that includes a cartridge 4 having a heater 30 disposed at the bottom of the cartridge and covering the open distal end 43 of the cartridge housing 41. In this embodiment, a first inlet 100A is disposed within the main housing 5, and ambient air 20A is directed directly from within the radially inwardly oriented portion 102A of the first channel toward the center of the main housing. Further, a second inlet 100B is disposed within the main housing 5, and ambient air 20B is directed directly from within the radially inwardly oriented second channel 102B toward the center of the main housing 5. The first channel and the second channel are integrated to form a single flow within the portion 103 disposed at the center of the first channel, and the integrated air flow is oriented to impinge perpendicularly onto the heater 30. A conductive contact 60 that is electrically coupled to a power source (not shown) located within the main housing 5 makes electrical contact with a corresponding contact of the heater 30 to supply current to the heater.

[0035] The air arriving via the first channel portion 103 passes through the heater 30 and mixes with the vapor and condensed droplets generated by heating the liquid within the aerosol-forming substrate 41 through the heater 30. The aerosol thus generated enters a 90-degree bend 45a, 45b in one of several elongated longitudinal portions 105 of the first channel 10 disposed between and along the cartridge 4 and is then directed toward the proximal end of the cartridge 4. Thereafter, the aerosol is guided to an outlet opening 12 disposed at the center within the proximal end of the mouthpiece 1 and exits therefrom.

[0036] Figure 3B is an exploded view for showing the system 8 in detail. It can be seen that a cartridge housing 4 with cross-sections 4A and 4B functions as a liquid reservoir and receives a liquid containing a high retention material or a high release material (HRM) 41 that orients the liquid towards the heater 30 for evaporation at the heater. A capillary disk 44, for example, a fibrous disk, is disposed between the HRM 41 and the heater 30. The material of the capillary disk 44 may be more heat resistant than the HRM 41 due to its proximity to the heater 30 in order to provide protection from thermal separation and decomposition of the HRM itself. When the heater is activated, the capillary disk 44 is kept in a wet state by the aerosol-forming liquid of the HRM to ensure the provision of liquid for vaporization.

[0037] The data shown in FIG. 4 demonstrates the relationship between air flow velocity and the cooling of the mesh heater. The cooling rate was measured using different mesh heaters (Reking (45 micrometers / 180 per inch), Haver (25 micrometers / 200 per inch) and 3-slice Warrington (25 micrometers / 250 per inch)). The measurement data for the Reking heater is indicated by crosshairs, the measurement data for the Haver heater is indicated by circles, and the measurement data for the 3-slice Warrington heater is indicated by triangles. All heaters were operated at 3 watts. The temperature was measured with a thermocouple coupled to the heater. As the flow rate, displayed in units of liters per minute [L / min] on the x-axis, was increased, the temperature measured at the mesh heater decreased. The typical size of the air flow within the aerosol generation system can be made close to standard smoking methods, such as the Health Canada smoking method, which results in significant cooling of the heater. Exemplary smoking methods, such as those of Health Canada, draw 55 mL of a mixture of air and vapor over a period of 2 seconds. An alternative method draws 55 mL over a period of 3 seconds. Neither exemplary smoking method can precisely mimic the behavior, but instead serves as a substitute for what an average user would inhale. To compensate for the higher cooling rate associated with the high velocity of the air flow and the perpendicular impingement of the air on the surface(s) of the heater 30, an increase in the supply of the current level to the heating element(s) may be required.

[0038] In the graph of FIG. 5, the average temperature of the heater versus time during a single puff is shown. Curve 60 represents the reference temperature data for the heater, where the total air flow is directed towards the heater. For the reference data, the heater is heated at 5 watts.

[0039] Figure 6 shows the effect of directing a vapor-mixed airflow along a portion of the cartridge housing 4 containing the liquid storage portion 41 on the temperature of the airflow transporting the aerosol at the mouthpiece outlet during a single puff. The data, as shown in FIGS. 2 and 3A, means that the ambient airflow enters through the outlet of the main housing and impinges perpendicular to the surface of a substantially flat heater disposed within a cross-section across the cartridge opening distal to the inhaled end of the mouthpiece, and the periphery of the downstream flow channel is curved to convey the airflow toward the inhaled end of the mouthpiece. The temperature curve 61 represents the temperature of the outlet air for a heater powered at 5 watts where the entire airflow impinges on and exits from the heater as arranged in FIG. 1. The temperature curve 71 also represents the temperature of the outlet air for a heater powered at 5 watts, but here the airflow passes close to the liquid storage portion to promote cooling, as shown in FIGS. 2 and 3A. In the arrangement of FIGS. 2 and 3A, due to heat transfer to the zone of the cartridge housing near the liquid storage portion, the temperature of the aerosol-transporting airflow at the proximal outlets of the main housing 5 and the mouthpiece 1 is significantly lower. Typically, the "fresh" air mixed into the airflow transporting the aerosol is at room temperature.

[0040] During a single puff, there may also be a significant difference in the ratio (Pvapor / Psaturation) of the vapor pressure to the saturation pressure of the glycerol solution at the outlet of the mouthpiece. This ratio is shown in Figure 7. Curve 72 represents the pressure data at the outlet of a 5-watt heater with all the airflow oriented towards the heater according to the arrangements of Figures 2 and 3A. Curve 62 represents the pressure data at the outlet of a 5-watt heater with all the airflow colliding with the heater according to the arrangement of Figure 1. This indicates a high degree of supersaturation of the glycerol solution, which is beneficial for the aerosolization of smaller droplets. In simulations, smaller droplet sizes are clearly predicted for the cooler vapor of the split airflow embodiment compared to the vapor of the non-split or all-airflow embodiments. These simulation data 67 are shown in Figure 8 for a single puff at the outlet of the mouthpiece. The Y-axis represents the diameter ratio of the droplets to the total airflow system of the split airflow. This ratio is calculated and displayed as d_split / d_ref = T*Ln(S)ref / T*Ln(S)split vs. time (in seconds) during a single puff in the aerosol generation system, where T is the temperature expressed in Kelvin and S is the saturation ratio which is a function of Pv and P ∞ (T).

[0041] Figure 9a illustrates the first heater 30. The heater 30 is a fluid-permeable assembly of heating elements and includes a mesh 36 formed from 304L stainless steel, with a mesh size of approximately 400 mesh US (about 400 filaments per inch). The diameter of the filaments is approximately 16 micrometers. The mesh is connected to electrical contacts 32 separated from each other by a gap 33 and is formed of a copper foil or tin foil with a thickness of about 30 micrometers. The electrical contacts 32 are provided on a polyimide substrate 34 with a thickness of about 120 micrometers. The filaments forming the mesh define the gaps between the filaments. In this example, the width of the gap is approximately 37 micrometers, although larger or smaller gaps may be used. By using a mesh of these approximate dimensions, a meniscus of the aerosol-forming substrate can be formed within the gap, and the mesh of the heating element can draw out the aerosol-forming substrate by capillary action. The ratio of the area of the open portion of the mesh, i.e., the area of the gap, to the total area of the mesh is advantageously 25 - 56%. The total resistance of the heating element is approximately 1 ohm. The mesh provides most of this resistance so that most of the heat is generated by the mesh. In this example, the electrical resistance of the mesh is more than 100 times higher than that of the electrical contacts 32.

[0042] The substrate 34 is electrically insulated and, in this example, is formed from a polyimide sheet with a thickness of about 120 micrometers. The substrate is circular with a diameter of 8 millimeters. The mesh is rectangular with side lengths of 5 millimeters and 2 millimeters. These dimensions enable the fabrication of a complete system with dimensions and shape similar to those of a conventional cigarette or cigar. Another example of dimensions that have been found to be effective is a circular substrate with a diameter of 5 millimeters and a rectangular mesh of 1 millimeter × 4 millimeters.

[0043] Figure 9b illustrates an alternative heater assembly. In the heating element of Figure 8b, the conductive heat-generating filament 37 is directly coupled to the substrate 34, and then the contacts 32 are coupled to the filament. The contacts 32 are separated from each other by an insulating gap 33 as before and are formed from a copper foil having a thickness of about 30 micrometers. As shown in Figure 8a, the same arrangement of substrate filaments and contacts can also be used for the mesh type heater. Having the contacts as the outermost layer can be beneficial in providing a reliable electrical contact with the power source.

[0044] Returning to Figures 1 - 3B, advantageously, the capillary material 41 is oriented to carry liquid within the housing 4 to the heater 30. When the cartridge is assembled, the heater filaments 36, 37, 38 may contact the capillary material 41, and the aerosol-forming substrate can be carried directly to the mesh heater.

[0045] In use, the heating element operates by resistive heating. Current passes through filaments 36, 37, 38 based on the control of a control electronics circuit (not shown) to heat the filaments within a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32, 35 and electrical connectors (not shown) such that a high temperature is localized to the filaments. The system may be configured to generate heat by providing current to the heating element in response to the user's puffing, or may be configured to continuously generate heat while the device is in the "on" state.

[0046] Different materials for the filaments may be appropriate for different systems. For example, in a continuous heating system, graphite filaments are appropriate because they have a relatively low specific heat capacity and are compatible with low current heating. In a system that operates by puffing where heat is generated in short bursts using high current pulses, stainless steel filaments having a high specific heat capacity may be more appropriate.

[0047] In the above-described cartridge system explained with reference to FIGS. 1 to 3B, the cartridge housing 4 may be, for example, a separate cartridge container in addition to the cartridge housing explained with reference to FIG. 1. In particular, a cartridge containing a liquid is a pre-manufactured product, and may be inserted into a cartridge housing provided in an aerosol generating system in order to receive the pre-manufactured cartridge.

[0048] 1. An aerosol generating system, comprising: a liquid storage portion that holds a liquid aerosol generating substrate and includes a container for defining an opening; a heater assembly that extends across the opening along a cross-section and includes at least one electrically operating heating element; a first channel that defines a first flow path, a portion of the first channel being disposed with respect to the cross-section such that at least a portion of the first channel is oriented to direct air coming from outside the system to impinge on and cross a surface portion of the at least one heating element. 2. The aerosol generating system according to 1, further comprising a second channel that defines a second flow path, the first flow path and the second flow path merging before or along a portion of the first channel that is oriented to direct air to impinge on and cross the surface portion of the at least one heating element. 3. The aerosol generating system according to 1 or 2, wherein the portion of the first channel that is oriented to direct air to impinge on and cross the surface portion of the at least one heating element is orthogonal to the cross-section. 4. The aerosol generating system according to any one of 1 to 3, wherein the heater assembly includes a plurality of heating elements through which a common plane passes. 5. The aerosol generation system according to any one of 1 to 4, further comprising a capillary medium aligned with the opening and in contact with the heating assembly, wherein the liquid aerosol generation substrate is drawn to the at least one electrically operating heating element via the capillary medium. 6. The aerosol generation system according to 5, wherein the at least one electrically operating heating element comprises a plurality of conductive filaments. 7. The aerosol generation system according to any one of 1 to 6, comprising a main unit and a cartridge removably coupled to the main unit, wherein the liquid storage portion and the heater assembly are provided within the cartridge, and the main unit comprises a power source. 8. The aerosol generation system according to 7, wherein the main unit further defines at least one inlet for drawing ambient air from outside the system and at least a first portion of the first channel corresponding to the flow path to the heater assembly. 9. The aerosol generation system according to 7, wherein the cartridge further defines at least one inlet for drawing ambient air from outside the system and at least a first portion of the first channel corresponding to the flow path to the heater assembly. 10. The aerosol generation system according to 8 or 9, wherein the cartridge defines a second portion of the first channel in fluid communication with the first portion. 11. The aerosol generation system according to any one of 8 to 10, wherein the main unit defines a second portion of the first channel in fluid communication with the first portion. 12. The aerosol generation system according to any one of 1 to 11, wherein a portion of the first channel is dimensioned and arranged to convey air away from the heater assembly along an elongated channel between the liquid storage portion and an inner surface portion of the cartridge. 13. The aerosol generation system according to any one of 1 to 12, wherein a portion of the first channel is dimensioned and arranged to convey air that travels away from the heater assembly along the bend. 14. A method for guiding an air flow within an electrically operated aerosol generation system, the method comprising: supplying an aerosol generation substrate; orienting air coming from outside the system towards, and along, a heating element aligned with an opening in a container containing the aerosol generation substrate; and transporting the generated aerosol to a downstream end of the system.

Claims

1. An aerosol generation system (8), comprising: a liquid storage portion (4) having a container for holding a liquid aerosol generation substrate, the liquid storage portion defining an opening; a heater assembly (30) extending across the opening along a cross-section and having at least one electrically operated heating element; a capillary material in contact with or adjacent to the heating element and configured to convey the liquid aerosol generation substrate to the heating element; a first channel (10) defining a first flow path, a portion of the first channel (10) disposed at the center thereof being disposed with respect to the cross-section such that at least the portion of the first channel (10) disposed at the center is oriented to direct air coming from outside the system (8) to impinge on and cross a surface portion of the at least one heating element; comprising; the portion of the first channel (10) disposed at the center and the liquid storage portion are disposed on the opposite side of the heating element; the air is conveyed by the first flow path to impinge perpendicularly to the geometric center of the surface of the heating element; the system comprises a main unit and a cartridge removably connected to the main unit, the liquid storage portion and the heater assembly being provided in the cartridge, the main unit being provided with a power source; the cartridge further defining at least one inlet (100) for drawing ambient air from outside the system (8) and at least a first portion of the first channel (10) corresponding to a flow path to the heater assembly (30); an aerosol generation system.

2. The aerosol generation system (8) according to claim 1, wherein the portion of the first channel (10) oriented to direct air to impinge on and cross a surface portion of the at least one heating element is orthogonal to the cross-section.

3. The aerosol generation system (8) according to claim 1, wherein the capillary material is aligned with the opening and the liquid aerosol generation substrate is drawn through the capillary material to the at least one electrically operated heating element.

4. In the aerosol generation system (8) according to any one of claims 1 to 3, the cartridge defines a second portion of the first channel (10) that is in fluid communication with the first portion, the aerosol generation system.

5. An aerosol generation system according to any one of claims 1 to 4, further comprising a mouthpiece, wherein the opening of the container faces away from the mouthpiece, the aerosol generation system.

6. In the aerosol generation system according to any one of claims 1 to 5, the heater assembly is disposed at the distal end of the container, the aerosol generation system.

7. In the aerosol generation system (8) according to any one of claims 1 to 6, a portion of the first channel (10) is dimensioned and arranged to convey air away from the heater assembly (30) along a bend, the aerosol generation system.

8. In the aerosol generation system according to any one of claims 1 to 7, the capillary material comprises a ceramic material, the aerosol generation system.

9. In the aerosol generation system according to any one of claims 1 to 8, the heater assembly is a fluid-permeable heater assembly comprising one or more conductive heating elements, the aerosol generation system.

10. In the aerosol generation system according to claim 9, the fluid-permeable heater assembly comprises one or more heating elements through which a common plane passes, whereby the heater assembly is in a substantially flat orientation, the aerosol generation system.

11. In the aerosol generation system according to claim 9 or 10, the fluid-permeable heater assembly comprises a conductive filament pattern printed on a heat-resistant support component, the support component preferably being ceramic, the aerosol generation system.

12. An aerosol generation system according to any one of claims 1 to 11, wherein the first channel defines an air flow path extending orthogonally to the cross-section and the surface of the capillary material, the aerosol generation system.

13. In the aerosol generating system according to any one of claims 1 to 12, a part of the first channel is arranged with respect to the cross section, whereby at least a part of the first channel is oriented to cause air coming from the outside of the system to impinge on the central part of the at least one heating element and to cross the surface part of the at least one heating element, preferably providing an outward radial airflow across the heating element.

14. In the aerosol generating system according to any one of claims 1 to 13, the first channel consists of a plurality of first partial channels and / or the second channel consists of a plurality of first partial channels.

15. In the aerosol generating system according to any one of claims 1 to 14, the heating element partially or completely covers the opening.

16. A method for guiding an air flow in an electrically operating aerosol generating system (8), supplying a liquid aerosol generating substrate; supplying a capillary material that is in contact with or in proximity to the heating element and is configured to carry the liquid aerosol generating substrate to the heating element; orienting air coming from the outside of the system (8) through a first channel (10) that defines a first flow path so as to impinge perpendicularly on the geometric center of the surface of the heating element and on and along the heating element disposed in an opening in a container (4) having the liquid aerosol generating substrate, wherein a portion disposed at the center of the first channel (10) and a liquid storage portion are disposed on the opposite side of the heating element; carrying the generated aerosol to the downstream end of the system (8), the system comprises a main unit and a cartridge removably connected to the main unit, a heater assembly (30) comprising the liquid storage portion and the heating element is provided in the cartridge, and the main unit is provided with a power source. The cartridge further defines at least one inlet (100) for drawing ambient air from outside the system (8) and at least a first portion of the first channel (10) corresponding to the flow path for the heater assembly (30). Method.

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