Heater Assembly with Microporous Insulation

Abstract

The present invention relates to a heater assembly for an aerosol generating device. The heater assembly comprises a heating chamber for heating an aerosol-forming substrate. The heater assembly further comprises a heater casing. The heater casing is disposed around the heating chamber. The heater casing is further disposed radially spaced from the heating chamber. The heater casing further comprises an airtight space. The airtight space comprises a microporous insulating material. The present invention further relates to an aerosol generating device comprising the heater assembly, and further relates to an aerosol generating system comprising an aerosol generating device and an aerosol-forming substrate.

Description

[Technical field]

[0001] The present disclosure relates to a heater assembly for an aerosol generating device.The present disclosure further relates to an aerosol generating device.The present disclosure further relates to an aerosol generating system comprising an aerosol generating device and an aerosol-forming substrate. [Background technology]

[0002] It is known to provide an aerosol-generating device for generating an inhalable vapor. Such a device may heat an aerosol-forming substrate contained in the aerosol-generating article without combustion. The aerosol-generating article may have a rod shape for inserting the aerosol-generating article into the heating chamber of the aerosol-generating device. A heating element is typically disposed in or around the heating chamber for heating the aerosol-forming substrate after the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device.

[0003] Heat generated by the heating element may inadvertently dissipate from the heating chamber. Heat may dissipate to the environment or to other components of the aerosol generating system. Heat may inadvertently dissipate from the heating chamber by free air convection. Heat may inadvertently dissipate from the heating chamber by radiation. Heat may inadvertently dissipate from the heating chamber by thermal conduction through components of the aerosol generating device. Heat may inadvertently dissipate from the heating chamber by thermal conduction through components of the aerosol generating article, for example, through the aerosol-forming substrate. Heat dissipation from the heating chamber may cause heating of components of the device that are not intended to be heated. For example, the housing of the device that the user grips may become uncomfortably hot. Heat dissipation from the heating chamber may cause heat loss within the heating chamber. Heat loss within the heating chamber may result in less efficient heating. Excessive amounts of energy may be required to heat the heating chamber to the desired temperature.

[0004] It would be desirable to have an aerosol generating device that can reduce heat loss from the heating chamber. It would be desirable to insulate the heating chamber from other components of the aerosol generating device. It would be desirable to have an aerosol generating device that can reduce heating of the outer housing of the device that is gripped by the user. It would be desirable to have an aerosol generating device that can provide effective insulation. It would be desirable to have an aerosol generating device that can provide insulation with low manufacturing costs. It would be desirable to have an aerosol generating device that can provide lightweight insulation. It would be desirable to have an aerosol generating device that can have improved insulation. It would be desirable to have an aerosol generating device that can have a reduced outer diameter of the heater casing. It would be desirable to have an aerosol generating device that can have a more compact device size. Summary of the Invention

[0005] According to one embodiment of the present invention, there is provided a heater assembly for an aerosol generating device. The heater assembly may comprise a heating chamber for heating an aerosol-forming substrate. The heater assembly may comprise a heater casing. The heater casing may be disposed around the heating chamber. The heater casing may be disposed radially spaced from the heating chamber. The heater casing may comprise an airtight space. The airtight space may comprise a microporous insulating material.

[0006] According to one embodiment of the present invention, there is provided a heater assembly for an aerosol generating device. The heater assembly comprises a heating chamber for heating an aerosol-forming substrate. The heater assembly further comprises a heater casing. The heater casing is disposed around the heating chamber. The heater casing is further disposed radially spaced from the heating chamber. The heater casing further comprises an airtight space. The airtight space comprises a microporous insulating material.

[0007] By providing an airtight space including a microporous insulating material around the heating chamber, heat loss due to air circulation between the inside of the heater casing and the outside air can be reduced or avoided. Also, by providing an airtight space including a microporous insulating material around the heating chamber, heat loss due to air convection in the airtight space can be reduced or avoided. Providing an airtight space including a microporous insulating material around the heating chamber can reduce radiative heat transfer. Advantageously, by providing an airtight space including a microporous insulating material around the heating chamber, insulation of the heating chamber against the outer surface of the heater casing can be improved. By providing an airtight space including a microporous insulating material around the heating chamber, a heater assembly for an aerosol generating device is provided that can reduce heat loss from the heating chamber. By providing an airtight space including a microporous insulating material around the heating chamber, a heater assembly for an aerosol generating device is provided that can reduce heating of the outer housing of the device that is gripped by the user. By providing an airtight space including a microporous insulating material around the heating chamber, a heater assembly for an aerosol generating device is provided that can provide effective insulation. Providing an airtight space containing a microporous insulating material may provide improved insulation at the operating temperatures of the aerosol generating device compared to an airtight hollow space.

[0008] "Operating temperature" depends on the type of aerosol-generating device and the aerosol-forming substrate used. The operating temperature of the aerosol-generating device may range from 150 to 300 degrees Celsius. The operating temperature of the aerosol-generating device may range from 200 to 230 degrees Celsius. The operating temperature of the aerosol-generating device may not exceed 280 degrees Celsius.

[0009] The airtight hollow space may contain air as the insulating material. However, the thermal conductivity of air increases with increasing temperature. The microporous insulating material contains small cavities or pores. Because air or other gaseous compositions are trapped in these cavities, the thermal conductivity of the microporous insulating material is lower with increasing temperature compared to air. The microporous insulating material may substantially maintain its thermal conductivity at the operating temperature of the aerosol generating device compared to its thermal conductivity at room temperature. The lower thermal conductivity of the microporous insulating material provides better insulation.

[0010] Due to better insulation, a heater casing including a microporous insulating material can have a reduced outer diameter. Providing a heater casing with an airtight space including a microporous insulating material can result in an aerosol generating device that can have a more compact device size.

[0011] As used herein, the terms "upstream" and "downstream" are used to describe the relative location of components or parts of components of an aerosol generating device with respect to the direction in which air flows through the aerosol generating device during its use. An aerosol generating device according to the invention comprises a proximal end through which aerosol exits the device during use. The proximal end of the aerosol generating device may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or parts of components of an aerosol generating device may be described as being upstream or downstream of each other based on their relative location with respect to the airflow path of the aerosol generating device.

[0012] The proximal end of a heater assembly according to the invention is configured to be disposed within an aerosol generating device in a direction towards the mouth or downstream end of the device. The distal end of a heater assembly according to the invention is configured to be disposed within an aerosol generating device in a direction towards the distal or upstream end of the device. The longitudinal axis of the heating chamber may extend between the proximal end of the heating chamber and the distal end of the heating chamber. The longitudinal axis of the heating chamber may extend between the proximal end of the heater assembly and the distal end of the heater assembly.

[0013] The heating chamber may be configured to at least partially receive the aerosol-forming substrate. The heating chamber may comprise a cavity into which the aerosol-forming substrate may be inserted. The aerosol-forming substrate may be part of an aerosol-generating article. The cavity may have a shape corresponding to the shape of the aerosol-generating article to be received therein. The cavity may have a circular cross-section. The cavity may have an elliptical or rectangular cross-section. The cavity may have an inner diameter corresponding to the outer diameter of the aerosol-generating article.

[0014] The heating chamber may comprise an opening at a proximal end thereof for receiving the aerosol-forming substrate. The opening may also serve as an air outlet. The heating chamber may comprise an air inlet at a distal end thereof.

[0015] The heating chamber may have an elongated shape. The heating chamber may be a hollow tube. The hollow tube may be formed from a wall of the heating chamber. The wall of the heating chamber may include or be made of a metal or alloy. The wall of the heating chamber may include or be made of stainless steel.

[0016] The heater casing may be radially spaced a distance d from the heating chamber. The distance d may be measured in a direction perpendicular to a longitudinal axis of the heating chamber. The heating chamber may comprise a heating chamber wall. The heater casing may comprise a heater casing wall. The distance d may be measured radially between a heating chamber wall and a heater casing wall. The distance d may be measured radially between an outer side of the heating chamber wall and an inner side of the heater casing wall.

[0017] The distance d between the heating chamber and the heater casing may be between 1.5 mm and 7 mm. The distance between the heating chamber and the heater casing may be between 2 mm and 4 mm, preferably about 3.1 mm.

[0018] The heater casing may be coaxially aligned about the heating chamber. The heating chamber and the heater casing may have matching shapes. The matching shapes may enable providing a constant radial distance d between the heater casing and the heating chamber.

[0019] The heater casing wall may match the shape of the heater chamber wall along the longitudinal axis of the heater chamber such that the distance d may be approximately constant. For example, the heater chamber may be a hollow tube and the heater casing wall may be a cylindrical wall that is coaxially aligned around the heater chamber. The distance d may be measured radially between the outer diameter of the hollow tube of the heater chamber and the inner diameter of the cylindrical wall of the heater casing. For example, the heater chamber may be a hollow truncated cone and the heater casing wall may be a conical wall that is coaxially aligned. Those skilled in the art will appreciate that other types of matching shapes are possible. For example, the matching shapes may be curved or wavy or may include a combination of different shapes along the longitudinal axis of the heater chamber.

[0020] The heating chamber and the heater casing may have deviating shapes. The shape of the heater casing wall may deviate to some extent from the shape of the heating chamber wall along the longitudinal axis of the heating chamber. The shape of the heater casing wall may deviate from the shape of the heating chamber wall along the longitudinal axis of the heating chamber such that the distance d does not vary by more than 1 millimeter along the longitudinal axis of the heating chamber. For example, the heating chamber may be a right conical hollow cylinder and the heater casing wall may be a slightly conical hollow cylinder that is coaxially aligned around the heating chamber. Due to the conical shape of the heater casing wall, the distance d may vary by 1 millimeter or less along the longitudinal axis of the heating chamber.

[0021] The outer diameter of the heater casing may be measured perpendicular to the longitudinal axis of the heating chamber. The outer diameter of the heater casing may be between 8 millimeters and 20 millimeters, preferably between 14 millimeters and 18 millimeters, preferably about 16 millimeters.

[0022] The outer diameter of the heating chamber may be measured in a direction perpendicular to the longitudinal axis of the heating chamber. The ratio of the outer diameter of the heater casing to the outer diameter of the heating chamber may be between 1.3 and 3.5, preferably between 1.5 and 2.5, and more preferably about 2.0. In particular, in one embodiment, the outer diameter of the heating chamber may be about 5.6 millimeters and the outer diameter of the heater casing may be about 17 millimeters, resulting in a ratio of about 3.0. In one embodiment, the outer diameter of the heating chamber may be about 5.6 millimeters and the outer diameter of the heater casing may be about 16.5 millimeters, resulting in a ratio of about 2.95. In one embodiment, the outer diameter of the heating chamber may be about 7.6 millimeters and the outer diameter of the heater casing may be about 16.5 millimeters, resulting in a ratio of about 2.17.

[0023] The airtight space is hermetically sealed from the outside air, in other words, the interior of the airtight space is not fluidly connected to the outside air, thereby avoiding heat loss due to gas circulation between the airtight space and the air outside the heater assembly.

[0024] The airtight space may be at ambient pressure. The gas pressure in the airtight space may be between 0.9 bar and 1.1 bar, preferably about 1.0 bar. The airtight space may be filled with the gaseous composition at about ambient pressure, at about 20 degrees Celsius. As known to those skilled in the art, temperature-dependent variations in gas pressure in the airtight space may occur. Providing an airtight space at ambient pressure may be less expensive than producing a vacuum airtight space under vacuum. Vacuum-based insulation may be more expensive to produce.

[0025] It has been found that a hermetic hollow space with a distance d between 1.5 mm and 7 mm sufficiently reduces heat loss. When providing such a distance d, the air or other gaseous composition enclosed within the hermetic space may be considered as still air. Still air, or non-moving air, further reduces air convection within the hermetic space. Heat loss due to air convection within the hermetic space may be reduced.

[0026] The thermal conductivity of air increases with increasing temperature. At 25 degrees Celsius the thermal conductivity of air is approximately 0.0262 W / m·K. At an operating temperature of 280 degrees Celsius the thermal conductivity of air is already approximately 0.043 W / m·K. Therefore, using air as the only insulating material in an airtight hollow space requires an air gap of relatively large thickness to provide sufficient insulation.

[0027] The microporous insulating material may have a lower thermal conductivity than air at room temperature. At high temperatures, the difference between the thermal conductivity of air and the thermal conductivity of the microporous insulating material may be even greater. The thermal conductivity of the microporous insulating material may not increase as rapidly as that of air. The microporous insulating material may maintain approximately its thermal conductivity even at high temperatures. For example, the microporous insulating material may have a thermal conductivity of 0.018 W / m·K at 20 degrees Celsius. At 200 degrees Celsius, the thermal conductivity is 0.022 W / m·K. At a temperature of 400 degrees Celsius, the thermal conductivity increases to 0.028 W / m·K according to ASTM C177. The thermal conductivity of this exemplary microporous insulating material is approximately the same as air at room temperature, even higher than the maximum operating temperature of the aerosol generating device. The lower the thermal conductivity, the better the insulation.

[0028] An airtight space containing an insulating material with low thermal conductivity may have a smaller thickness while still providing sufficient insulation. An airtight space containing a microporous insulating material instead of an airtight hollow space containing only air may have a smaller distance d. A smaller distance d may result in a smaller outer diameter of the aerosol generating device.

[0029] Microporous insulating materials suitable for the present invention may have pore diameters less than 100 nanometers, preferably less than 70 nanometers, more preferably less than 50 nanometers, more preferably less than 20 nanometers, more preferably less than 2 nanometers.

[0030] The microporous insulating material may be inorganic. The microporous insulating material may be ceramic. The microporous insulating material may include silica (SiO2). The microporous insulating material may include pyrogenic silica. The microporous insulating material may include opacifiers and other components such as fibers. The opacifiers may scatter infrared radiation, thereby reducing the transmission of infrared radiation.

[0031] The microporous insulating material of the present disclosure has a porosity of 500 kg / m 3 Less than 400 kg / m 3 less than 300 kg / m3 It may have a nominal density of less than 100 nm.

[0032] The microporous insulating material of the present invention may have a thermal conductivity at 20 degrees Celsius of less than 0.05 W / m·K, preferably less than 0.04 W / m·K, more preferably less than 0.03 W / m·K, more preferably less than 0.02 W / m·K according to ASTM C177. The microporous insulating material may have a thermal conductivity at a temperature of 280 degrees Celsius of less than 0.05 W / m·K, preferably less than 0.04 W / m·K, more preferably less than 0.03 W / m·K according to ASTM C177. The thermal conductivity of the microporous insulating material may be increased by up to 40 percent, preferably up to 30 percent, more preferably up to 20 percent at a temperature of 280 degrees Celsius compared to the thermal conductivity of the microporous insulating material at 20 degrees Celsius.

[0033] At the operating temperature of the aerosol generating device, an airtight hollow space containing a microporous insulating material may have a lower thermal conductivity than the same airtight hollow space that instead contains ambient air.

[0034] The airtight space may be completely filled with a microporous insulating material.

[0035] Alternatively, the airtight space may not be completely filled with the microporous insulating material. By not completely filling the airtight space with the microporous insulating material, the weight of the aerosol generating device may be reduced. However, the airtight space may be at least partially filled with the microporous insulating material. The airtight space may further be at least partially filled with a gaseous composition. The gaseous composition may be at ambient pressure. The gaseous composition may be air. The gaseous composition may include one or more of nitrogen, argon, carbon dioxide, oxygen, krypton, sulfur hexafluoride or mixtures thereof, or other suitable gaseous compositions.

[0036] By additionally providing the gaseous composition in the airtight space, the weight of the aerosol generating device may be reduced. By providing the gaseous composition in the airtight space, the manufacturing costs may be reduced.

[0037] The volume of the airtight space filled with the microporous insulating material may be 30 volume percent, 40 volume percent, 50 volume percent, 60 volume percent, 70 volume percent, 80 volume percent, or 90 volume percent. The ratio of the microporous insulating material to the gaseous composition may depend on the operating temperature of the aerosol generating device. An aerosol generating device with a high operating temperature may require more microporous insulating material.

[0038] The airtight space may include at least one air gap. The gaseous composition may be provided within the air gap.

[0039] The airtight space may include one air gap. The airtight space may include two air gaps. The airtight space may include three air gaps. The microporous insulating material may be radially sandwiched between the two air gaps.

[0040] The air gap may have a thickness measured perpendicular to the longitudinal axis of the heating chamber, the thickness of the air gap may be between 0.5 millimeters and 4 millimeters, preferably between 1 millimeter and 3 millimeters, and more preferably about 2 millimeters.

[0041] The one or more air gaps may be in the microporous insulation material. The one or more air gaps may extend in a direction parallel to the longitudinal axis of the aerosol generating device. The one or more air gaps may have a longitudinal extension that is the same as or shorter than the longitudinal extension of the microporous insulation material. The one or more air gaps may have a circular cross section. Alternatively, the one or more air gaps may not extend around the entire circumference of the microporous insulation material. The one or more air gaps may be completely surrounded by the microporous insulation material. The one or more air gaps may be in direct contact with the first and second connecting walls, as described in more detail below. The one or more air gaps may be in direct contact with the heating chamber. The one or more air gaps may be in direct contact with the heater casing.

[0042] By providing an air gap within the airtight space, the weight of the aerosol generating device may be reduced. By providing an air gap within the airtight space, the manufacturing costs may be reduced.

[0043] The microporous insulating material may be in direct contact with the heating chamber. The microporous insulating material may be surrounded by an air gap. The temperature around the heating chamber may decrease radially with increasing distance from the longitudinal axis of the heating chamber. The microporous insulating material may provide better insulation at higher temperatures than air, for example. An assembly in which the microporous insulating material is in direct contact with the heating chamber surrounded by an air gap may have improved insulation over an assembly arranged the other way around.

[0044] The heater assembly may further comprise a first connecting wall connecting the heating chamber and the heater casing, and a second connecting wall connecting the heating chamber and the heater casing. The airtight space may be defined between the heating chamber, the heater casing, and the first and second connecting walls. The airtight space may be limited by the heating chamber, the heater casing, and the first and second connecting walls. The first and second connecting walls may provide for a simple assembly of the airtight space. The first and second connecting walls may provide for a simple manufacture of the airtight space. By providing the first and second connecting walls, a defined distance d of the heater casing from the heating chamber may be ensured. By providing the first and second connecting walls, a correct positioning of the microporous insulating material may be ensured. The first and second connecting walls may be in contact with the microporous insulating material, thereby preventing heat loss by air convection over the proximal and distal ends of the microporous insulating material.

[0045] Each of the first and second connecting walls may extend between a wall of the heating chamber and a wall of the heater casing. The first and second connecting walls may sealingly connect the heater casing to an outer wall of the heating chamber. The connecting walls may be oriented perpendicular to a longitudinal axis of the heating chamber. The first connecting wall may be a proximal connecting wall. The second connecting wall may be a distal connecting wall.

[0046] The microporous insulating material may be in direct contact with the heating chamber. The microporous insulating material may be in direct contact with the heater casing. The microporous insulating material may be in direct contact with the first and second connecting walls. The microporous insulating material may be in direct contact with the heating chamber and the heater casing. The microporous insulating material may be in direct contact with the heating chamber, the heater casing, and the first and second connecting walls. The microporous insulating material may be attached between the first and second connecting walls. The microporous insulating material may be disposed over the distance between the first and second connecting walls. The microporous insulating material may be attached between the first and second connecting walls while not being in contact with one or both of the heater casing and the heating chamber.

[0047] The microporous insulating material may have elongated extensions. The microporous insulating material may extend parallel to the longitudinal axis of the heating chamber. The microporous insulating material may be a hollow tube extending around the heating chamber.

[0048] The microporous insulating material may have a thickness measured in a direction perpendicular to the longitudinal axis of the heating chamber. The microporous insulating material may have a thickness equal to the distance d. The thickness of the microporous insulating material may be between 1 mm and 7 mm, preferably between 2 mm and 6 mm, and more preferably between 3 mm and 5 mm.

[0049] The microporous insulating material may be formed from a single element. Alternatively, the microporous insulating material may be formed from at least two insulating elements. The microporous insulating material may be formed from two insulating elements. The microporous insulating material may be formed from at least a first insulating element including at least a first connecting element and a second insulating element including at least a second connecting element. The first and second connecting elements may be configured as mating connecting elements. When connected, the mating connecting elements may allow for connection of the first and second microporous insulating elements. The connected first and second connecting elements may result in the overall insulating material forming a hollow tube. The hollow tube may have an inner diameter corresponding to the outer diameter of the heating chamber. Providing the microporous insulating material from two insulating elements may provide for easy assembly of the microporous insulating material around the heating chamber. By forming the microporous insulating material from two insulating elements, a perfect form fit between the microporous insulating material and the heating chamber may be provided. By providing a perfect form fit between the microporous insulating material and the heating chamber, better insulation can be ensured.

[0050] The first and second connection elements may be configured as male and female connection elements, as form-fit connection elements, as snap-fit ​​connection elements, as bayonet connection elements or combinations thereof, or other commonly used connection elements known to those skilled in the art. The first connection element may include a male connection element and the second connection element may include a female connection element. The first connection element and the second connection element may include a form-fit connection element. The first connection element and the second connection element may include a snap-fit ​​connection element. The first connection element and the second connection element may include a bayonet connection element.

[0051] The microporous insulating material may be configured as a two-piece assembly. The two-piece assembly may include a first and a second insulating element. The first and second insulating elements may be in the form of, for example, hollow semi-cylindrical elements. The hollow semi-cylindrical elements may include mating first and second connecting elements. When connected, the hollow semi-cylindrical elements may form a single hollow tube. The inner diameter of the hollow tube may have the same size as the outer diameter of the heating chamber. This may ensure easy assembly. On the other hand, a microporous insulating material formed as one element having an inner diameter the same as the outer diameter of the heating chamber may be more difficult to assemble around the heating chamber due to friction. Close proximity or direct contact of the microporous insulating material with the heating chamber may improve the insulation of the heating chamber.

[0052] The heating chamber may include a temperature sensor. The temperature sensor may be on the top of the heating chamber. The microporous insulating material may have a shape that matches the temperature sensor. The microporous insulating material may have a cavity facing the temperature sensor. The microporous insulating material may be completely closed around the heating chamber. The temperature sensor may be surrounded by the microporous insulating material. The temperature sensor may be sandwiched between the heating chamber and the microporous insulating material.

[0053] The heater assembly may further comprise a heating element. The heating chamber may contain a heating element.

[0054] The heating element may be disposed at least partially around the heating chamber. The heating element may be disposed at least partially around the wall of the heating chamber. The heating element is preferably disposed completely coaxially around the outer periphery of the wall of the heating chamber. The heating element may be disposed along at least a portion of the longitudinal axis of the heating chamber.

[0055] The heating element may comprise one or more conductive tracks on an electrically insulating substrate. The one or more conductive tracks may be resistive heating tracks. The one or more conductive tracks may be configured as an inductively heated susceptor. The electrically insulating substrate may be a flexible substrate.

[0056] The heating element may be flexible and may be wrapped around the heating chamber. The heating element may be disposed between the heating chamber and the heater casing.

[0057] The microporous insulating material may have a longitudinal extension that is the same as or greater than the longitudinal extension of the heating element, thereby ensuring adequate insulation of the heat generated by the heating element.

[0058] The microporous insulating material may extend around the heating element. The microporous insulating material may be in direct contact with the heating element.

[0059] In all aspects of the present disclosure, the heating element may comprise an electrically resistive material.Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composites made of ceramic and metal materials.Such composites may comprise doped or undoped ceramics.

[0060] As described, in any of the aspects of the present disclosure, the heating element may be part of the heating chamber of the heater assembly for the aerosol generating device. The heater assembly may comprise an internal heating element, or an external heating element, or both an internal heating element and an external heating element, where "internal" and "external" refer to the aerosol-forming substrate. The internal heating element may take any suitable form. For example, the internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different conductive portions or electrically resistive metal tubes. Alternatively, the internal heating element may be one or more heating needles or rods that pass through the center of the aerosol-forming substrate. Other alternatives include heating wires or filaments, such as Ni-Cr (nickel chromium), platinum, tungsten, or alloy wires or heating plates. Optionally, the internal heating element may be disposed in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal that has a well-defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as a ceramic material, and then sandwiched in another insulating material, such as glass. A heater formed in this manner may be used to both heat the heating element and monitor its temperature during operation.

[0061] The external heating element may take any suitable form. For example, the external heating element may take the form of one or more flexible heating foils on a dielectric substrate such as polyimide. The flexible heating foils can be shaped to fit the periphery of the substrate receiving cavity. Alternatively, the external heating element may take the form of a metal grid(s), a flexible printed circuit board, a molded integrated circuit device (MID), a ceramic heater, a flexible carbon fiber heater, or may be formed using a coating technique such as plasma deposition on a substrate of suitable shape. The external heating element may also be formed using a metal that has a well-defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating material. An external heating element formed in this manner may be used both to heat the external heating element and to monitor the temperature of the external heating element during operation.

[0062] The heating element advantageously heats the aerosol-forming substrate by thermal conduction. The heating element may be in at least partial contact with the substrate or at least partial contact with the carrier on which the substrate is deposited. Alternatively, heat from either an internal or external heating element may be conducted to the substrate by a thermally conductive element.

[0063] In operation, the aerosol-forming substrate may be completely contained within the aerosol-generating device, in which case a user may puff on the mouthpiece of the aerosol-generating device. Alternatively, in operation, a smoking article containing the aerosol-forming substrate may be partially contained within the aerosol-generating device, in which case a user may puff on the smoking article directly.

[0064] The heating element may be configured as an induction heating element. The induction heating element may comprise an induction coil and a susceptor. Generally, the susceptor is a material that has the ability to generate heat when penetrated by an alternating magnetic field. According to the present invention, the susceptor may be conductive, or magnetic, or both conductive and magnetic. The alternating magnetic field generated by one or several induction coils heats the susceptor, which then transfers the heat to the aerosol-forming substrate so that the aerosol is formed. The heat transfer may be mainly by thermal conduction. Such heat transfer is best when the susceptor is in intimate thermal contact with the aerosol-forming substrate. When an induction heating element is employed, it may be configured as an internal heating element as described herein or as an external heater as described herein. When the induction heating element is configured as an internal heating element, the susceptor element is preferably configured as a pin or blade for penetrating the aerosol-generating article. When the induction heating element is configured as an external heating element, the susceptor element is preferably configured as a cylindrical susceptor that at least partially surrounds or forms a sidewall of the cavity.

[0065] The heating chamber may comprise a central region comprising the heating element. The term central region refers to the longitudinal direction. The heating chamber may further comprise a proximal region and a distal region. The proximal region and the distal region may be spaced apart from the heating element in the longitudinal direction. In use, the proximal region and the distal region may be cooler than the central region of the heating chamber. The first connecting wall may contact the heating chamber in the proximal region and the second connecting wall may contact the heating chamber in the distal region. Thus, the first and second connecting walls may contact the heating chamber at the coldest point of the heating chamber in use. Thereby, heat loss from the heating chamber to the connecting walls and the heater casing may be further reduced. Thermal insulation may be further improved.

[0066] The walls of the heating chamber may be made of stainless steel, which may advantageously enhance the effect that during use the proximal and distal regions may be cooler than the central region of the heating chamber.

[0067] The heater casing wall thickness may be less than about 2 millimeters. The heater casing wall thickness may be less than 1.2 millimeters, preferably about 0.8 millimeters. One or both of the first and second connecting walls may be less than 1.2 millimeters, preferably about 0.8 millimeters thick. Having such thin walls may minimize the thermal mass of the heater casing. This may further reduce heat loss from the heating chamber.

[0068] One or more of the heater casing wall and the first and second connecting walls may be made of a low thermal conductivity material. This may further reduce heat loss from the heating chamber. The heater casing wall may include or be made of a plastic material. The first and second connecting walls may include or be made of a plastic material. The plastic material may include one or both of polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyphenylenesulfone (PPSU). Preferably, the plastic material includes polyphenylenesulfone (PPSU).

[0069] The inside of the heater casing wall may include a metal coating. The inside of one or both of the first connecting wall and the second connecting wall may include a metal coating. The metal coating may reduce the emissivity of the inside of the wall. For example, the emissivity of a PEEK wall may be reduced from about 0.95 to about 0.4. The metal coating may reflect thermal radiation radiated from the heating chamber. The metal coating may provide additional insulation of the heating chamber against the outside of the heater casing. The metal coating may be a low emissivity metal coating. The metal coating may include one or more of aluminum, gold, and silver.

[0070] The present invention further relates to an aerosol generating device comprising a heater assembly as described herein.

[0071] The aerosol generating device preferably comprises a power supply configured to provide power to the heating element. The power supply preferably comprises a power source. The power source is preferably a battery, such as a lithium ion battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for about six minutes, or a multiple of six minutes. In another example, the power source may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation of the heater assembly.

[0072] The power supply may comprise control electronics. The control electronics may comprise a microcontroller. The microcontroller is preferably a programmable microcontroller. The electrical circuit may include further electronic components. The electrical circuit may be configured to regulate the supply of power to the heater assembly. Power may be supplied to the heater assembly continuously after activation of the system or may be supplied intermittently (e.g., between puffs). Power may be supplied to the heater assembly in the form of current pulses.

[0073] The present invention further relates to an aerosol-generating system comprising an aerosol-generating device as described herein and an aerosol-forming substrate configured to be at least partially inserted into a heated chamber. The aerosol-forming substrate may be part of an aerosol-generating article, which may be configured to be at least partially inserted into a heated chamber.

[0074] The term "aerosol-forming substrate" as used herein refers to a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating or burning the aerosol-forming substrate. As an alternative to heating or burning, in some cases the volatile compound may be released by a chemical reaction or by mechanical stimulation such as ultrasound. The aerosol-forming substrate may be solid or liquid, or may include both solid and liquid components. The aerosol-forming substrate may be part of an aerosol-generating article.

[0075] The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate may include both solid and liquid components. The aerosol-forming substrate may include a tobacco-containing material that contains volatile tobacco flavor compounds that are released from the substrate upon heating. The aerosol-forming substrate may include a non-tobacco material. The aerosol-forming substrate may include an aerosol former that facilitates the formation of a dense and stable aerosol. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0076] As used herein, the term "aerosol-generating article" refers to an article that includes an aerosol-forming substrate capable of emitting a volatile compound capable of forming an aerosol. The aerosol-generating article may be disposable.

[0077] The term "aerosol-generating device" as used herein refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-generating device may interact with one or both of an aerosol-generating article that includes an aerosol-forming substrate and a cartridge that includes an aerosol-forming substrate. In some examples, the aerosol-generating device may heat the aerosol-forming substrate to facilitate the release of volatile compounds from the substrate. An electrically operated aerosol-generating device may include an atomizer, such as an electric heater, for heating the aerosol-forming substrate to form an aerosol.

[0078] The term "aerosol-generating system" as used herein refers to the combination of an aerosol-generating device with an aerosol-forming substrate. When the aerosol-forming substrate forms part of an aerosol-generating article, the aerosol-generating system refers to the combination of an aerosol-generating device with an aerosol-generating article. In an aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device work together to generate an aerosol.

[0079] The following provides a non-exhaustive list of non-limiting examples, any one or more of the features of which may be combined with any one or more features of the other examples, embodiments, or aspects described herein. EXAMPLES

[0080] Example A: 1. A heater assembly for an aerosol generating device, comprising: a heating chamber for heating the aerosol-forming substrate; and a heater casing disposed about the heating chamber, the heater casing being radially spaced from the heating chamber, the heater casing including an airtight space, the airtight space including a microporous insulating material. Example B: A heater assembly according to embodiment A, further comprising a first connecting wall connecting the heating chamber and the heater casing, and a second connecting wall connecting the heating chamber and the heater casing, wherein an airtight space is defined between the heating chamber, the heater casing, and the first and second connecting walls. Example C: A heater assembly according to embodiment B, wherein the connecting wall is oriented perpendicular to the longitudinal axis of the heating chamber. Example D: The heater assembly according to any of embodiments A-C, wherein the airtight space is at ambient pressure. Example E: A heater assembly according to any of embodiments A-D, wherein the airtight space is at least partially filled with a microporous insulating material. Example F: The heater assembly according to any of Examples A-E, wherein the airtight space is at least partially filled with the gaseous composition at ambient pressure. Example G: The heater assembly according to any of embodiments A-F, wherein the airtight space includes at least one air gap. Example H: A heater assembly according to embodiment G, in which the microporous insulating material is radially sandwiched between two air gaps. Example I: The heater assembly according to any of embodiments A-H, wherein the microporous insulating material is in direct contact with the heating chamber. Example J: A heater assembly according to any of embodiments A-I, wherein the microporous insulating material is in direct contact with the heater casing. Example K: A heater assembly according to any of Examples A-J, wherein the microporous insulating material is in direct contact with the first and second connecting walls of Example B. Example L: The heater assembly according to any of embodiments A-K, wherein the microporous insulating material is in direct contact with the heating chamber, the heater casing, and the first and second connecting walls of embodiment B. Example M: A heater assembly according to any of embodiments A-L, wherein the microporous insulating material is formed from at least one first insulating element including at least one first connecting element, and a second insulating element including at least one second connecting element, the first and second connecting elements being configured as mating connecting elements. Example N: The heater assembly according to embodiment M, wherein the first connecting element comprises a male connecting element and the second connecting element comprises a female connecting element. Example O: The heater assembly according to embodiment M or N, wherein the first connecting element and the second connecting element comprise form-fit connecting elements. Example P: The heater assembly according to any of embodiments MO, wherein the first connecting element and the second connecting element comprise snap-fit ​​connecting elements. Example Q: The heater assembly according to any of embodiments MP, wherein the first connecting element and the second connecting element comprise bayonet connecting elements. Example R: A heater assembly according to any of embodiments A-Q, wherein the microporous insulating material has elongated extensions. Example S: The heater assembly according to any of embodiments A-R, wherein the microporous insulating material extends parallel to the longitudinal axis of the heating chamber. Example T: The heater assembly according to any of embodiments A to S, wherein the distance between the heating chamber and the heater casing is between 1.5 mm and 7 mm, preferably between 2 mm and 4 mm, preferably about 3.1 mm. Example U: The heater assembly according to any of embodiments A-T, further comprising a heating element. Example V: The heater assembly according to embodiment U, wherein the heating element is disposed at least partially around the heating chamber. Example W: A heater assembly according to embodiment U or V, wherein the microporous insulating material has a longitudinal extension that is the same as or greater than the longitudinal extension of the heating element. Example X: The heater assembly according to any one of embodiments U-W, wherein the heating element is flexible and wrapped around the heating chamber. Example Y: The heater assembly of any one of embodiments U-X, wherein the heating element is disposed between the heating chamber and the heater casing. Example Z: The heater assembly according to any one of embodiments U-Y, wherein the heating element comprises one or more conductive tracks on an electrically insulating substrate. Example AA: The heater assembly according to any of Examples A to Z, wherein the ratio of the outer diameter of the heater casing to the outer diameter of the heating chamber is between 1.3 and 3.5, preferably between 1.5 and 2.5, and more preferably about 2.0. Example AB: A heater assembly according to any of embodiments A-AA, wherein the microporous insulating material has a thermal conductivity of less than 0.05 W / m·K, preferably less than 0.04 W / m·K, and more preferably less than 0.03 W / m·K at a temperature of 280 degrees Celsius. Example AC: A heater assembly according to any of Examples A-AB, wherein the thermal conductivity of the microporous insulating material is increased by up to 40 percent, preferably up to 30 percent, and more preferably up to 20 percent at a temperature of 280 degrees Celsius compared to the thermal conductivity of the microporous insulating material at room temperature. Example A-D: The heater assembly according to any of embodiments A-AC, wherein the microporous insulating material has a pore diameter of less than 100 nanometers, preferably less than 70 nanometers, more preferably less than 50 nanometers, more preferably less than 20 nanometers, more preferably less than 2 nanometers. Example AE: The heater assembly according to any of embodiments A-AD, wherein the heating chamber has an elongated shape, preferably the heating chamber is a hollow tube. Example AF: The heating chamber comprises a central region provided with the heating element of Example U; A proximal region; a distal region, the proximal and distal regions are longitudinally spaced from the heating element; The heater assembly according to any of Examples A-AE, wherein the first connecting wall of Example B contacts the heating chamber in a proximal region and the second connecting wall of Example B contacts the heating chamber in a distal region. Example AG: A heater assembly according to any of claims A-AF, wherein the inside of the heater casing wall comprises a metal coating, and optionally the heating chamber wall comprises stainless steel. Example AH: A heater assembly according to any of Examples A-AG, wherein the thickness of the heater casing wall and one or more of the first and second connecting walls of claim 2 is less than 2 millimeters, preferably less than 1.2 millimeters, preferably about 0.8 millimeters. Example AI: The heater assembly according to any of Examples A-AH, wherein the heater casing wall and one or more of the first and second connecting walls of Example B comprise a plastic material, preferably polyaryletherketone (PAEK), polyetheretherketone (PEEK), or polyphenylenesulfone (PPSU), more preferably polyphenylenesulfone (PPSU). Example AJ: An aerosol generating device comprising a heater assembly according to any one of Examples A to AI. Example AK: An aerosol-generating system comprising an aerosol-generating device according to Example AJ and an aerosol-forming substrate configured to be at least partially received within a heated chamber.

[0081] Features described with respect to one embodiment may be equally applied to other embodiments of the invention.

[0082] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0083] [Figure 1] FIG. 1 illustrates one embodiment of a heater assembly for an aerosol generating device. [Diagram 2] FIG. 2 illustrates one embodiment of the heating chamber of the heater assembly. [Diagram 3] FIG. 3 illustrates one embodiment of a heater assembly for an aerosol generating device. [Figure 4] FIG. 4 illustrates one embodiment of a heater assembly for an aerosol generating device. [Diagram 5] FIG. 5 illustrates one embodiment of a heater assembly for an aerosol generating device. [Figure 6] FIG. 6 illustrates one embodiment of a heater assembly for an aerosol generating device. [Figure 7] FIG. 7 illustrates one embodiment of a microporous insulating material for a heater assembly for an aerosol generating device. [Figure 8] FIG. 8 shows one embodiment of an aerosol generating device. [Figure 9] FIG. 9 shows one embodiment of an aerosol generating device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] FIG. 1 shows a schematic of a heater assembly 10. The heater assembly 10 comprises a heating chamber 12 for heating an aerosol-forming substrate. The heating chamber 12 has an elongated shape. The heating chamber 12 comprises a heating chamber wall 14 surrounding a cavity for insertion of an aerosol-forming substrate. The heating chamber wall 14 forms a hollow tube. The heater assembly 10 further comprises a heater casing. The heater casing is coaxially disposed around the heating chamber 12. The heater casing comprises a cylindrical wall of a heater casing 16. The heater casing is further disposed radially spaced a distance d from the heating chamber 12. The distance d is measured radially between the outer diameter of the hollow tube formed by the heating chamber wall 14 and the inner diameter of the cylindrical wall of the heater casing 16. The heating chamber wall 14 and the heater casing 16 walls have matching shapes. Thereby, the distance d is constant along the longitudinal axis of the heating chamber 12.

[0085] The heater assembly 10 further comprises a first connecting wall 18 at a proximal end of the heater assembly 10. The heater assembly 10 further comprises a second connecting wall 20 at a distal end of the heater assembly 10. The first and second connecting walls 18, 20 are oriented perpendicular to the longitudinal axis of the heating chamber 12. The heater assembly 10 further comprises an airtight space 22. The airtight space 22 is defined between the heating chamber wall 14, the heater casing wall 16, and the first and second connecting walls 18, 20.

[0086] FIG. 2 shows one embodiment of the heating chamber 12. The heating chamber 12 comprises a central region comprising a heating element. The heating element is disposed partially around the heating chamber 12. The walls 14 of the heating chamber are metal tubes. The heating element is flexible and wrapped around the metal tube. The heating element comprises an electrically insulating flexible substrate 26 with an electrically conductive heating track 24. In the embodiment shown, the proximal and distal edge portions of the flexible substrate 26 are not covered by the heating track 24. In other embodiments, different regions of the flexible substrate 26, or even the entire surface, may be covered by the heating track 24. The proximal and distal regions 28 and 30 of the heating chamber 12 are longitudinally spaced from the heating element.

[0087] Figure 3 shows one embodiment of a heater assembly 10 comprising the heating chamber 12 of Figure 2. A heating element is disposed between the heating chamber 12 and a heater casing.

[0088] First and second connecting walls 18, 20 sealingly connect the heater casing wall 16 with the heating chamber wall 14, thereby hermetically enclosing the airtight space 22.

[0089] The first and second connecting walls 18, 20 contact the heating chamber 12 at a proximal region 28 and a distal region 30, respectively. The first and second connecting walls 18, 20 contact the heating chamber 12 at a location spaced from the heating element. Hence, the first and second connecting walls 18, 20 contact the heating chamber at the coldest point 12 of the heating chamber when heated during use. Thereby, heat loss due to heat transfer from the heating chamber 12 to the connecting walls 18, 20 and the heater casing by thermal conduction is further reduced. Thermal insulation may be further improved.

[0090] The airtight space 22 includes a microporous insulating material 32. The microporous insulating material 32 may be, for example, MICROSIL microporous insulation manufactured by ZIRCAR Ceramics, Inc., Excelfrax® manufactured by Unifrax I LLC, Microtherm 1000 grade manufactured by Promat Inc., or other commercially available microporous insulating material.

[0091] In the embodiment shown in Fig. 3, the entire airtight space 22 is filled with a microporous insulating material 32. The microporous insulating material 32 is in contact with the heating chamber wall 14, the heating track 24, the first and second connecting walls 18 and 20, and the heater casing wall 16. Although not shown, the microporous insulating material 32 shown in Fig. 3 may also include one or more air gaps extending in a direction parallel to the longitudinal axis of the aerosol generating device. These air gaps may be in direct contact with the heating chamber wall 14, the heater casing wall 16, or the first and second connecting walls 18, 20. These air gaps may have a shorter longitudinal extension than the microporous insulating material 32.

[0092] Figures 4, 5 and 6 show alternative embodiments in which the airtight space 22 is only partially filled with the microporous insulating material 32. The main elements are similar to the heater assembly of Figure 3. In the embodiments shown in Figures 4, 5 and 6, the airtight space 22 includes at least one additional air gap 34. In all of these embodiments, the microporous insulating material 32 is in contact with the first connecting wall 18 and the second connecting wall 20. The microporous insulating material 32 may be attached on the first connecting wall 18 and the second connecting wall 20.

[0093] 4, the heater assembly is shown with an air gap 34 extending around the heating chamber 12. The microporous insulation material 32 extends around the air gap 34, radially spaced from the heating chamber 12. The microporous insulation material 32 is in direct contact with the heater casing wall 16.

[0094] 5 shows an alternative embodiment in which the microporous insulation material 32 is in direct contact with the heating chamber 12. An air gap 34 extends around the microporous insulation material 32 radially spaced from the heating chamber 12. The air gap 34 is in direct contact with the heater casing wall 16.

[0095] 6 shows an alternative embodiment in which the airtight space 22 includes two air gaps 34. One air gap 34 extends around and directly connects with the heating chamber 12. The microporous insulating material 32 extends at a radial distance from the air gap 34. An additional air gap 34 then extends around the microporous insulating material 32 at a radial distance from the microporous insulating material 32. The microporous insulating material 32 is radially sandwiched between the two air gaps 34.

[0096] The airtight space 22 shown in Figures 3, 4, 5 and 6 may be filled with the microporous insulating material 32 in different ratios. For example, half of the volume of the airtight space 22 is filled with the microporous insulating material 32. However, other ratios are possible. For example, 20 volume percent, 30 volume percent, 40 volume percent, 50 volume percent, 60 volume percent, 70 volume percent, 80 volume percent, or 90 volume percent of the airtight space 22 is filled with the microporous insulating material 32.

[0097] FIG. 7 shows a two-piece assembly of the microporous insulating material 32. All of the heater assemblies 10 shown in FIGS. 3, 4, 5 and 6 can be equipped with the two-piece assembly of FIG. 7. However, the two-piece assembly is particularly suitable for the embodiment of FIGS. 3 and 5. As can be seen in FIG. 7, the microporous insulating material 32 is formed from a first insulating element 36 having a first connecting element 40 and a second insulating element 38 having a second connecting element 42. The first connecting element 40 and the second connecting element 42 are configured as mating connecting elements. When the two first insulating element 36 and the second insulating element 38 are connected, the first connecting element 40 and the second connecting element 42 are connected to each other. The connection of the first connecting element 40 and the second connecting element 42 provides a direct contact of the first insulating element 36 and the second insulating element 38. The first insulating element 36 and the second insulating element 38 can have a hollow semi-cylindrical design as shown in FIG. 7. However, other shapes and configurations are possible. When connected, the hollow half-cylinder design provides a hollow tube. The hollow tube can have an inner diameter the same as the outer diameter of the heating chamber 12. The hollow tube may also have an inner diameter the same as the outer diameter of the heating chamber 12 and the heating track 24 together. This two-piece assembly allows the microporous insulation material 32 to have a perfect fit with the heating chamber 12 and the heating track 24 around the heating chamber. Furthermore, if the heating chamber includes a temperature sensor (not shown), the inner shape of the microporous insulation material 32 can be configured to fit the temperature sensor. The microporous insulation material 32 may include a cavity facing the sensor. The cavity may have the same volume and inverse shape as the temperature sensor has. The microporous insulation material 32 may be completely closed around the heating chamber 12 and the heating track 24. Using a hollow tube that includes only a single element of the microporous insulation material 32 may not provide such a perfect fit with the heating chamber 12.

[0098] Figure 8 shows an embodiment of an aerosol generating device comprising the heater assembly 10 of Figure 3. The aerosol generating device further comprises a power supply. The power supply includes a power source 44 and control electronics 46. The power source 44 may be a rechargeable battery. In the embodiment of Figure 8, the heater casing wall 16 forms part of the outer housing 48 of the aerosol generating device.

[0099] At the opening 50, the aerosol-forming substrate may be at least partially inserted into the heating chamber 12. The aerosol-forming substrate may be part of the aerosol-generating article. Figure 9 shows an embodiment of an aerosol generating device that includes the heater assembly 10 of Figure 3. Unlike the embodiment of Figure 8, in the embodiment of Figure 9, the heater assembly 10 is disposed within a separate outer housing 48 of the aerosol generating device.

Claims

1. A heater assembly for an aerosol generator, comprising: a heating chamber for heating an aerosol-forming substrate; and a heater casing disposed around the heating chamber, the heater casing being spaced radially from the heating chamber, the heater casing including an airtight space containing a microporous insulating material.

2. The heater assembly according to claim 1, further comprising a first connecting wall connecting the heating chamber and the heater casing and a second connecting wall connecting the heating chamber and the heater casing, the airtight space being defined between the heating chamber, the heater casing, the first and second connecting walls.

3. The heater assembly according to claim 1, wherein the airtight space is at least partially filled with the microporous insulating material, preferably the airtight space is only partially filled with the microporous insulating material.

4. The heater assembly according to claim 1, wherein the airtight space includes at least one air gap.

5. The heater assembly according to claim 4, wherein the microporous insulating material is radially sandwiched between two air gaps.

6. The heater assembly according to claim 1, wherein the microporous insulating material is formed from at least one first insulating element including at least one first connecting element and at least one second insulating element including at least one second connecting element, the first and second connecting elements being configured as mating connecting elements.

7. The heater assembly according to claim 6, wherein the first and second connecting elements are configured as male and female connecting elements, form-fitting connecting elements, snap-fitting connecting elements, or bayonet connecting elements.

8. The heater assembly according to claim 1, wherein the microporous insulating material has an elongated extension, and preferably the microporous insulating material extends parallel to the longitudinal axis of the heating chamber.

9. The heater assembly according to claim 1, wherein the distance between the heating chamber and the heater casing is from 1.5 millimeters to 7 millimeters, preferably from 2 millimeters to 4 millimeters, preferably about 3.1 millimeters.

10. The heater assembly according to claim 1, further comprising a heating element, wherein the heating element is preferably disposed at least partially around the heating chamber, and the microporous heat insulating material preferably has a major axis extension that is the same as or larger than the major axis extension of the heating element in the longitudinal axis direction of the heating element.

11. The heater assembly according to claim 1, wherein the microporous heat insulating material has a thermal conductivity of less than 0.05 W / m·K, preferably less than 0.04 W / m·K, more preferably less than 0.03 W / m·K at a temperature of 280 °C.

12. The heater assembly according to claim 1, wherein the thermal conductivity of the microporous heat insulating material increases by a maximum of 40%, preferably a maximum of 30%, more preferably a maximum of 20% at a temperature of 280 °C compared to the thermal conductivity of the microporous heat insulating material at 20 °C.

13. The heater assembly according to claim 1, wherein the microporous heat insulating material has a pore size of less than 100 nanometers, preferably less than 70 nanometers, more preferably less than 50 nanometers, more preferably less than 20 nanometers, more preferably less than 2 nanometers.

14. An aerosol generating device comprising the heater assembly according to any one of claims 1 to 13.

15. An aerosol generating system comprising the aerosol generating device according to claim 14 and an aerosol forming substrate configured to be at least partially received in the heating chamber.

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