Split airflow system for an electrically heated smoking system and method for directing airflow within an electrically heated smoking system

Abstract

To provide an electrically heated smoking system and a method for guiding an airflow inside the electrically heated smoking system to improve the efficiency of the electrically heated smoking system.SOLUTION: Provided are a split airflow system and a method for an electrically heated smoking system for generating aerosol, wherein the split airflow system having a downstream end includes a first channel defining a first flow route and a second channel defining a second flow route. The first flow route directs ambient air from outside the system to the downstream end of the system. The second flow route directs ambient air from outside the system toward a preferably substantially flat, fluid permeable, heating element before conveying the ambient air to the downstream end. The first channel and the second channel define a total volume of ambient air passing through the system, and the first channel provides at least 50 percent of the total volume of ambient air passing through the system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrically heated smoking system and a method for directing airflow within an electrically heated smoking system. [Background technology]

[0002] Some aerosol-generating systems, such as electrically operated smoking devices, may include a battery and control electronics, a cartridge containing a source of aerosol-forming substrate, and an electrically operated vaporizer. A substance is vaporized from the aerosol-forming substrate, for example, by a heater. While a user smokes at the mouth end, airflow passes through the heating element, entraining the vaporized liquid and directing it through the mouthpiece to the mouth end of the mouthpiece.

[0003] Airflow through the heater can have a cooling effect on the heater, which can result in reduced vaporization of the liquid or increased energy required to keep the heater at a temperature sufficient to vaporize an amount of liquid, such as to achieve a desired amount of aerosol.

[0004] Therefore, there is a need for an electrically heated smoking system and a method for directing airflow within an electrically heated smoking system that improves the efficiency of the electrically heated smoking system. Summary of the Invention

[0005] According to a first aspect, a split airflow system for an electrically heated smoking system for generating aerosol is provided. The split airflow system has a downstream end and includes a first channel defining a first flow path and a second channel defining a second flow path. The first and second channels are at least partially distinct channels. The first flow path directs ambient air from outside the system to the downstream end of the system. The second flow path directs ambient air from outside the system toward a heating element, preferably a substantially planar, fluid-permeable heating element, before conveying the ambient air to the downstream end. The first and second channels define a total volume of ambient air passing through the system, with the first channel providing at least 50 percent of the total volume of ambient air passing through the system.

[0006] The liquid vaporized by the heating element is collected by ambient air flowing into the second channel and carried to the downstream end of the split airflow system. The ambient air is guided into the split airflow system and passes through the heating element to capture the liquid vaporized by the heating element. This ambient air cools the heating element. The cooling effect depends not only on the temperature of the ambient air but also on the amount of ambient air that contacts the heating element. The split airflow system of the present invention provides a first channel for directing ambient air along a first flow path that does not pass through the heating element. The first channel also terminates at the proximal end of the system, preferably at the mouth end of the electrically operated smoking system mouthpiece. However, ambient air entering the split airflow system is divided along a first flow path and a second flow path within the first channel and a second channel, respectively. The first channel preferably bypasses at least a portion of the second channel located upstream of the heating element. This allows only a portion of the total volume of ambient air entering the system to pass through the heating element. Another portion of the total volume of ambient air is guided directly to the downstream end of the split airflow system, i.e., without passing through the heating element.

[0007] In this way, a variable volume of ambient air can bypass the heating element. The amount of ambient air that passes through the heating element and can have a cooling effect on the heating element can be varied and controlled. Because half, or preferably less than half, of the total volume of ambient air passes through the heating element, the heating element is not cooled as much as if the entire volume of ambient air passed through the heating element. Therefore, the heating element can operate with relatively low energy. This saves energy and can also lead to longer operating times or smaller batteries for smoking systems with split airflow systems. Furthermore, if the heating element can operate with lower energy, the risk of malfunction of the heating element due to, for example, a short circuit or high temperature spike can be reduced or eliminated.

[0008] Furthermore, because the ambient air in the first channel has not passed through a heating element, this ambient air is cooler than the ambient air carrying the aerosol in the second channel. Therefore, the ambient air in the first channel can have a cooling effect on the ambient air carrying the aerosol. This effect is particularly evident when the first flow path merges with the second flow path before reaching the downstream end of the system. The first airflow then mixes with the second airflow inside, for example, inside the mouthpiece, and is further rapidly cooled. This can result in supersaturation of the air with the vaporized liquid. This can also result in the formation of relatively small aerosol droplets.

[0009] Preferably, the first channel provides between about 50 percent and about 95 percent of the total volume of ambient air passing through the split airflow system. More preferably, the first channel provides between about 65 percent and about 95 percent, and even more preferably between about 85 percent and about 89 percent, of the total volume of ambient air passing through the split airflow system.

[0010] It has been found that a small airflow through the heating element is sufficient to entrain the vaporized liquid and guide it to the downstream end of the system. The smaller the ambient airflow through the heating element, the less heat loss due to cooling of the heating element by the passing airflow. The above flow rates in the second channel have been shown to entrain the vaporized liquid particularly well, while at the same time slightly cooling the heating element. The stated volume percentage values ​​relative to the total volume of ambient air are preferably applied to aerosol-generating smoking systems equipped with a substantially planar heating element, more preferably a substantially planar fluid-permeable heating element, for example, a heating element with multiple conductive filaments, such as a mesh heating element.

[0011] The amount of ambient air passing through the second channel and past the heating element can be varied and can be adapted, for example, to the type of heating element applied or the amount of vaporized liquid available. For example, the volume of ambient air passing through the heating element can be adapted to the total area effectively heated by the heating element.

[0012] As a general rule, whenever the term "about" is used throughout this specification in connection with a particular value, it is understood that the value following the term "about" does not have to have that exact particular value due to technical considerations. However, the term "about" when used in connection with a particular value is always understood to include and explicitly disclose the particular value that follows the term "about."

[0013] As used herein, the terms "upstream" and "downstream" refer to the direction of airflow within the system. The upstream and downstream ends of the system are defined relative to the airflow when a user draws on the proximal or mouth end of the aerosol-generating smoking article. Air is drawn into the system at the upstream end, passes downstream through the system, and exits the system at the proximal or downstream end. As used herein, the terms "proximal" and "distal" refer to the location of an element relative to a direction toward or away from the consumer. Thus, the proximal end of the mouthpiece of an aerosol-generating system corresponds to the mouth end of the mouthpiece. The distal opening of the cartridge housing therefore corresponds to the location of the opening located in the cartridge housing facing away from the consumer.

[0014] The term "substantially planar" heating element is used throughout this specification to refer to a heating element that is in the form of a substantially two-dimensional topological manifold. Thus, a substantially planar heating element extends two-dimensionally along a surface that is substantially greater than the third dimension. In particular, the dimension of a substantially flat heating element in two dimensions within its surface is at least five times greater than the third dimension perpendicular to the surface. An example of a substantially planar heating element is a structure between two substantially parallel imaginary surfaces, where the distance between these two imaginary surfaces is substantially less than the extension within the surface. In some preferred embodiments, a substantially planar heating element is flat. In other embodiments, a substantially planar heating element is curved along one or more dimensions, for example, forming a dome or bridge shape. Planar heating elements allow for easier handling during manufacturing and provide a robust structure.

[0015] The heating element used in a split airflow system or smoking system may be, for example, a wick coil heater, as is well known in the art, where a coil is wrapped around a wick, which is immersed in the liquid to be vaporized, and the liquid is transported by capillary action outside the cartridge to the portion of the wick where the coil is wrapped around the wick, causing the wick to heat.

[0016] Preferably, a fluid-permeable heating element is used. Fluid-permeable heating elements are suitable for vaporizing liquids in different types of cartridges. For example, as a liquid aerosol-forming substrate, the cartridge may include a liquid or a carrier material containing a liquid (e.g., a capillary material). Such carrier material and capillary material are preferably active liquid carriers and are oriented within the cartridge to transport the liquid to the heating element. The filament arrangement of the heating element is positioned in close proximity to the liquid or the capillary material containing the liquid so that the heat generated by the heating element can vaporize the liquid. The filament arrangement and the aerosol-forming substrate are preferably positioned so 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.

[0017] The fluid-permeable heating element is preferably a substantially planar heating element. Such a heating element may be, for example, a flat coil embedded within a porous ceramic or mesh heater, where a mesh or other filament arrangement is disposed across the heater's openings. The heating element may, for example, comprise a conductive mesh or coil pattern printed on a heat-resistant support component. The support component may be ceramic, polyetheretherketone (PEEK), or other heat-resistant ceramics and polymers that do not thermally decompose or release volatile elements at temperatures below 200°C, preferably below 150°C.

[0018] The term "filament" is used throughout this specification to mean an electrical path disposed between two electrical contacts. A filament may optionally branch into several paths or filaments, or several electrical paths may merge into one path. A filament may have a round, square, flat, or any other cross-sectional configuration. A filament may be arranged in a straight or curved manner.

[0019] The term "filament arrangement" is used throughout this specification to mean an arrangement of one or, preferably, multiple filaments. The filament arrangement can be, for example, a series of filaments arranged parallel to one another. Preferably, the filaments can form a mesh. The mesh can be woven or nonwoven. The filament arrangement preferably has a thickness between about 0.5 micrometers and 500 micrometers. The filament arrangement can be, for example, in the form of an array of parallel or crossed conductive filaments. The filaments can be formed integrally with electrical contacts, for example, formed from a conductive foil, e.g., stainless steel foil, etched to define the filaments.

[0020] The heating element vaporizes the liquid from the cartridge or cartridge housing containing the aerosol-forming substrate. The aerosol-forming substrate is a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound can be released by heating the aerosol-forming substrate.

[0021] The aerosol-forming substrate may comprise a plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material, including volatile tobacco flavor compounds that are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise a homogenized plant-derived material. The aerosol-forming substrate may comprise a homogenized tobacco material. The aerosol-forming substrate may comprise at least one aerosol former. The aerosol-forming agent is any suitable known compound or mixture of compounds that is substantially resistant to thermal decomposition at the operating temperatures of the system, which facilitates the formation of a dense, stable aerosol in use. 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 glycerin), 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 glycerin, most preferred). The aerosol-forming substrate may contain other additives and ingredients, such as flavorings.

[0022] The aerosol-forming substrate is transported to the heating element via a capillary material that is in contact with or adjacent to the heating element. The capillary material may have a fibrous or spongy structure. Preferably, the capillary material 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 be generally aligned to transport the liquid to the heating element. Alternatively, the capillary material may comprise a spongy or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which the liquid can travel by capillary action. The capillary material may comprise any suitable material or combination of materials. Examples of suitable materials include spongy or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metal or plastic materials, and fibrous materials made from spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene, or polypropylene fibers, nylon fibers, or ceramics). The capillary material may have any suitable capillary and porosity for use with different liquid physical properties. Liquids have physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure, that allow them to move through a capillary device by capillary action.

[0023] The capillary material may be in contact with the conductive filaments of the heating element. The capillary material may extend into the gaps between the filaments. The heating element may draw the liquid aerosol-forming substrate into the gaps by capillary action. The capillary material may be in contact with the conductive filaments over substantially the entire length of the opening of the heating element.

[0024] The heating element can be provided within a heating assembly that includes a support element. The heating assembly can include two or more different capillary materials, where a first capillary material in contact with the heating element has a higher thermal decomposition temperature and a second capillary material in contact with the first capillary material but not the heating element has a lower thermal decomposition temperature. The first capillary material effectively serves as a spacer, separating the heating element from the second capillary material so that the second capillary material is not exposed to temperatures above its thermal decomposition temperature. As used herein, "thermal decomposition temperature" refers to the temperature at which a material begins to decompose and lose mass by generating gaseous byproducts. 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 wick performance than the first capillary material. The second capillary material may be less expensive or have a higher filling capacity than the first capillary material. The second capillary material may be polypropylene.

[0025] In accordance with aspects of the split airflow system of the present invention, the first channel merges with an end of the second channel such that the first flow path merges with the second flow path after the second flow path directs the ambient air past the heating element, i.e., after the first flow path merges with the second flow path downstream of the heating element.

[0026] In such an embodiment, the ambient air may leave the downstream end of the split airflow system or, for example, the mouthpiece of the smoking system at one or several common exit openings. The most downstream portion of the second channel is preferably identical to the first channel. This may simplify the manufacture of the smoking system. For example, the mouthpiece may be provided with a single additional hole in the mouthpiece wall that extends to the second channel within the mouthpiece, forming the first channel. This also allows existing mouthpieces to be adapted to the split airflow system without the need to reconstruct the entire mouthpiece. The ambient air containing the aerosol mixes with "fresh" ambient air introduced into the system by the first flow path, thereby cooling the ambient air containing the aerosol. The cooler air supports the formation of smaller aerosol droplet sizes compared to the same air at a higher temperature. The cooler air is believed to support the supersaturation of the air with vaporized liquid. Supersaturation has an effect on the size of droplets formed in the supersaturated air.

[0027] According to an alternative embodiment of the split airflow system of the present invention, the first channel and the second channel form distinct channels such that the first and second flow paths direct ambient air from outside the system to the downstream end of the system, separated from one another. Thus, ambient air is drawn into the split airflow system, guided into the system, passes through it, and exits the system along completely separate flow paths. This ensures that the ambient air passing through the heating element and the ambient air bypassing the heating element do not compete with or affect each other. Having a separate first channel provides numerous structural possibilities for directing ambient air through the system or through the mouthpiece, independent of the aerosol-carrying ambient air in the second channel.

[0028] According to another aspect of the split airflow system of the present invention, at least a portion of the second channel and the heating element are positioned perpendicular to each other such that at least a portion of the second channel directs ambient air to impinge on the heating element at a right angle.

[0029] Allowing ambient air to impinge on the heating element is an efficient way to direct the ambient air toward the heating element and carry the aerosol away from the heating element. In particular, if the ambient air impinges on the center of the heating element, a uniform airflow toward the heating element can be provided radially outward. The ambient air can impinge only on the center of the heating element.

[0030] In the split airflow system according to the present invention, at least a portion of the second channel located downstream of the heating element can be arranged around the heating element, preferably only around the heating element. Multiple second channel portions are preferably arranged around the heating element. This allows vapor-laden ambient air to leave the heating element around the heating element, for example, longitudinally, along the periphery of the housing or mouthpiece of the electrically heated smoking system. Both the large area through which the vapor-laden ambient air is guided and its proximity to the environment support cooling of the vapor-laden air and aerosol formation. When at least a channel portion of the first channel is arranged parallel to at least one portion of the circumferentially arranged second channel located downstream of the heating element, additional cooling can be provided by fresh ambient air flowing through the first channel portion and thermal contact between the respective first and second channel portions. Multiple first channel portions are preferably arranged longitudinally along the periphery of the mouthpiece. The arrangement of peripheral-only channel portions leaves open the option of, for example, having other channels arranged only in the center, or having central and peripheral channel portions, or radially arranged channel portions connecting the central channel portion with the environment.

[0031] The first and second flow paths can be selected to achieve a desired result, such as a predetermined airflow split with a predetermined air volume passing through each channel. For example, the length or diameter of the channels can be varied to achieve a predetermined resistance to draw (RTD). The first and second flow paths can also be selected according to the setup of the aerosol-generating smoking system and 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 the cartridge housing containing the aerosol-forming substrate. Depending on the orientation of the cartridge in the aerosol-generating smoking system, the open end of the cartridge housing can be positioned facing the mouthpiece or facing away from the mouthpiece. Accordingly, a heating element for heating the aerosol-forming substrate is positioned at the proximal or distal end of the housing. Preferably, the liquid is vaporized at the open distal end of the mouthpiece, and the heating element is positioned between the cartridge and the mouthpiece.

[0032] Therefore, the first flow path and the first channel are preferably located entirely within the mouthpiece of the smoking system. Therefore, the first air inlet is preferably located within the sidewall of the mouthpiece, while one or several outlets of the first channel are preferably located within the proximal or mouth end of the mouthpiece. The second flow path depends on the location of the heating element within the smoking system. For example, if the heating element is located at the open proximal end of the cartridge housing, for example, covering the proximal end of the cartridge (top version), the second channel may be located entirely within the mouthpiece.

[0033] The first channel and the second channel may branch into several channel portions, or several channel portions of the first channel or the second channel may merge into a single first channel or a single second channel, respectively. Furthermore, the first channel may be comprised of several first partial channels, and the second channel may be comprised of several second partial channels. Thus, the sum of the first partial channels provides the ambient air volume of the first channel, and the sum of the second partial channels provides the ambient air volume of the second channel. The total number of air inlets for both the first and second partial channels may be preferably 2 to 10, more preferably 6 to 10, and most preferably 8 to 10. For example, the total number of first partial channels supplying the ambient air volume of the first channel may have 7 or 9 inlets in fluid communication with the first channel, and the total number of second partial channels supplying the ambient air volume of the second channel may be via 1 or 2 inlets in fluid communication with the second channel.

[0034] In embodiments in which the heating element is located at the open distal end of the cartridge housing, for example, to cover the open distal end of the cartridge (bottom version), the second flow path typically begins at a more distal location within the smoking system, for example, in the region of the distal end of the cartridge housing. The second air inlet of the second channel is located, for example, within the main housing of the system. Ambient air is then directed into the system, passing through the heating element at the distal end of the cartridge and mixing in the vapor generated by heating the aerosol-forming substrate within the cartridge. The air-containing aerosol can then be guided along the cartridge between the cartridge housing and the main housing to the downstream end of the system, where it mixes with the ambient air from the first flow path (either before or upon reaching the downstream end).

[0035] An inlet opening of the second channel, located in the distal end region of the cartridge housing, may also be provided in the upper version (i.e., embodiment) in which the heating element is located at the proximal end of the cartridge. The second flow path passes not only outside the cartridge but also through it. Ambient air then enters the semi-open wall of the cartridge, passes through the cartridge, and exits the cartridge by passing through the heating element located at the proximal end of the cartridge. Thereby, the ambient air may pass through one or more channels located within the aerosol-forming substrate or solid aerosol-forming substrate, such that the ambient air passes through a channel next to the substrate rather than through the substrate itself.

[0036] At least one semi-open inlet is provided in a side wall of the cartridge housing, preferably the wall opposite the heating element, preferably the bottom wall, to allow ambient air to enter the cartridge, and the semi-open inlet allows air to enter the cartridge but does not allow air or liquid to exit the cartridge through the semi-open inlet.

[0037] A semi-open inlet may be, for example, a semi-permeable membrane that allows air to pass through in only one direction but prevents air and liquid from leaking in the opposite direction. A semi-open inlet may also be, for example, a one-way valve. Preferably, a semi-open inlet only allows air to pass through the inlet if certain conditions are met, such as minimal denting of the cartridge and the volume of air passing through the valve or membrane.

[0038] Such one-way valves may be, for example, commercially available valves, such as those used in medical devices, e.g., LMS Mediflow One-Way, LMS SureFlow One-Way or LMS Check Valves (across a membrane). Suitable membranes for use in cartridges where airflow passes through the cartridge are, for example, vented membranes used in medical devices (e.g., Qosina Ref. 11066, vented cap with hydrophobic filter), or valves used in baby bottles.

[0039] The valve and membrane may be made of any material suitable for use in electrically heated smoking systems. Materials suitable for medical devices and FDA approved may be used, such as graphene, which has very high mechanical resistance and thermal stability over a wide temperature range. Preferably, the valve is made of a soft, elastic material so that one or more valves can be incorporated into the cartridge housing wall to prevent liquid leakage.

[0040] Passing ambient air through the substrate assists in aerosolization of the aerosol-forming substrate. During smoking, the cartridge may dent, activating the semi-open inlet. Ambient air then passes through the cartridge, preferably a high retention or high release material (HRM) or liquid, and across the heating element, thereby initiating and maintaining aerosolization of the liquid when the heating element sufficiently heats the liquid. Furthermore, the dent created during smoking may restrict the delivery of liquid to the heating element within a carrier material, such as a capillary material. Ambient airflow through the cartridge may equalize pressure differentials within the cartridge, thereby assisting unimpeded capillary action toward the heating element.

[0041] Additionally or alternatively, a semi-open inlet may be provided in one or more side walls of the cartridge housing, the semi-open inlet in the side wall providing a lateral airflow into the cartridge toward the open top end of the cartridge housing where the heating element is located. The lateral airflow preferably passes through the aerosol-forming substrate.

[0042] If the air inlet of the second channel is located within the mouthpiece, the path from the inlet to the heating element is kept short, thus possibly reducing the drawing resistance. Air can also be guided radially from one side of the heating element to the other, or, for example, from the peripheral side of the heating element to the center of the heating element.

[0043] The second flow path can provide a number of variations for supplying ambient air to the heating element and transporting the aerosol away from the heating element to the downstream end of the system. For example, a radial ambient air supply is preferably combined with a large central extraction. A central ambient air supply is preferably combined with a radial air distribution over the entire heating element surface, so that the aerosol-laden air is transported around the periphery to the downstream end. The second flow path can direct the ambient air to the heating element, for example, perpendicular to the heating element, preferably at the center of the heating element.

[0044] Airflow oriented circumferentially or parallel to the central portion of the heating element exhibits improved aerosolization in terms of smaller particle size and greater amounts of total particulate matter particles in the aerosol stream when compared to airflow impinging on the surface at angles greater than 0 degrees but less than 90 degrees. This may be due to lower levels of turbulence occurring at the heater element and airflow interface, improved aerosol generation by maximizing the heater overall (e.g., portions of the heater element other than the central portion contribute additional or increased aerosol volume), or increased wicking effect due to the increased volume of air moving across the heating element.

[0045] According to another aspect of the present invention, there is provided a method for directing an airflow in an electrically heated smoking system for generating an aerosol. The method includes the steps of directing ambient air from outside the system to a downstream end of the system along a first flow path, and directing the ambient air from outside the system toward a heating element, preferably a substantially planar, fluid-permeable heating element, before conveying the ambient air along a second flow path to the downstream end of the system. Thus, a total volume of the ambient air passes through the system along the first flow path and along the second flow path, and at least 50 percent of the total volume of the ambient air passing through the system passes through the first flow path.

[0046] According to an aspect of the method according to the invention, the method further includes combining the ambient air of the first flow path and the ambient air of the second flow path before they reach the downstream end of the system.

[0047] According to another aspect of the method according to the present invention, the method further comprises the step of maintaining the first flow path separated from the second flow path.

[0048] According to yet another aspect of the method according to the present invention, the method includes directing the ambient air in the second flow path so that the ambient air in the second flow path impinges substantially perpendicularly on the heating element.

[0049] Further aspects and advantages of the method according to the invention have been mentioned in connection with the split airflow system and smoking system according to the invention and will not be repeated here.

[0050] According to a further aspect of the method according to the invention, the method further comprises the steps of providing a liquid aerosol-forming substrate, heating the heating element thereby vaporizing the liquid from the aerosol-forming substrate to form an aerosol, and allowing the formed aerosol to be entrained in ambient air directed towards the heating element by a second flow path before the ambient air containing the aerosol is conveyed to the downstream end of the system.

[0051] According to another aspect of the method according to the present invention, the method further includes providing at least a portion of the first channel and at least a portion of the second channel within a mouthpiece of the system, wherein the downstream end of the system is the proximal end of the mouthpiece, directing ambient air within at least a portion of the second channel in a direction along a length of the mouthpiece toward the proximal end of the mouthpiece, reversing the direction of the ambient air within the second channel, and directing the ambient air toward the heating element to strike the heating element.

[0052] According to some embodiments of the method according to the present invention, the ambient air is directed through at least a portion of the second channel along a central axis of the mouthpiece so as to impinge substantially on the center of the heating element.

[0053] The method further includes directing the aerosol-laden ambient air from the center of the heating element, where the ambient air preferably strikes the heating element at a right angle, radially outward toward the periphery of the heating element and downstream of the periphery toward the outlet opening. Directing the aerosol-laden ambient air downstream of the periphery may be performed, for example, with a plurality of circumferentially arranged channel segments.

[0054] The method may include disposing a substantially planar fluid-permeable heating element within an electrically heated smoking system. The heating element is preferably disposed in such a manner as to face the open distal end of the smoking system's mouthpiece. The fluid-permeable heating element preferably comprises a plurality of electrically conductive filaments. The plurality of filaments, e.g., an array of parallel filaments or a mesh, provides adequate liquid vaporization and adequate permeability of the vaporized liquid due to the gaps between the filaments. Such filament or mesh heating elements are inexpensive to manufacture and robust, particularly compared to coil or wick heaters. The mesh heating element may be manufactured in a space-saving, substantially planar manner. The mesh heating element is also easy to handle, particularly during installation of the heating element or a cartridge equipped with the heating element.

[0055] According to yet another aspect of the present invention, there is also provided an electrically heated smoking system for generating aerosols, comprising the split airflow system described herein. The smoking system includes a storage portion including a housing for holding a liquid aerosol-forming substrate, the housing having an open end. The smoking system also includes a heating element, preferably a substantially planar, fluid-permeable heating element, extending across the open end of the housing and a mouthpiece disposed adjacent to the housing. The mouthpiece includes an elongated body including an open distal end facing the housing. The mouthpiece further includes a first channel disposed within the mouthpiece, the first channel including a first inlet opening disposed within a sidewall of the elongated body and an outlet opening disposed at a proximal end of the elongated body for defining a first flow path for directing ambient air from outside the system through the mouthpiece to an outlet opening. The mouthpiece also includes an end of a second channel extending between the open distal end of the elongated body and the proximal end of the elongated body. The second channel is disposed within the smoking system and defines a second flow path. The second flow path directs ambient air entering the smoking system toward the heating element, where the ambient air is capable of entraining the aerosol generated by vaporizing the liquid by heating the heating element before conveying the aerosol-laden ambient air to the proximal end of the elongated body of the mouthpiece. The first channel and the second channel define a total volume of ambient air passing through the smoking system, with the first channel providing at least 50 percent of the total volume of ambient air passing through the smoking system. Ambient air from outside the system is divided and flows along a first flow path within the first channel and along a second flow path within the second channel.

[0056] The heating element is preferably located between the mouthpiece and the aerosol-generating substrate.

[0057] In accordance with an aspect of the smoking system of the present invention, the first channel merges with the end of the second channel downstream of the open distal end of the elongate body, such that ambient air in the first channel does not pass through the heating element, and the first inlet opening of the first channel is fluidly connected to the outlet opening at the downstream end of the system, i.e., within the proximal end of the mouthpiece.

[0058] According to another aspect of the smoking system of the present invention, the second channel includes a second outlet opening disposed at a proximal end of the elongate body, the second outlet opening being separated from the outlet opening of the first channel.

[0059] According to a further aspect of the smoking system according to the present invention, the second inlet opening of the second channel is disposed within the side wall of the elongate body.

[0060] In the smoking system according to the present invention, the second channel may comprise at least one second channel portion located downstream of the heating element, which carries the aerosol-containing ambient air, and the at least one second channel portion is located longitudinally along the periphery of the housing or the periphery of the mouthpiece.

[0061] Aspects and advantages of the electrically heated smoking system have been described in relation to the split airflow system and method of directing airflow within the electrically heated smoking system and will not be repeated.

[0062] According to some embodiments of the smoking system of the present invention, the upstream portion of the second channel is arranged parallel to the side wall of the elongated body of the mouthpiece or the housing before the intermediate portion of the second channel is oriented in the radial direction of the elongated body. Such a flow path can be used, for example, to orient the ambient air so that it is guided substantially parallel to the portion of the ambient air already carrying the aerosol. This can achieve additional cooling of the aerosol by the ambient air.

[0063] According to another aspect of the smoking system of the present invention, the heating element is a fluid-permeable heating element comprising a plurality of conductive filaments.

[0064] According to a further aspect of the smoking system of the present invention, the second channel comprises a plurality of second channel ends arranged longitudinally along the periphery of the elongated body. The ambient air is preferably directed toward the center of the heating element. While the ambient air can provide uniform extraction of the aerosol from the heating element, the centrally directed ambient air can flow radially outward over the surface of the heating element. Furthermore, the aerosol-laden ambient air can be cooled over a large total surface area, which can further support the formation of small-sized aerosol particles.

[0065] The invention will be further described with reference to embodiments, which are illustrated by the following diagrams. [Brief explanation of the drawings]

[0066] [Figure 1] FIG. 1 shows an embodiment of a split airflow system. [Figure 2] FIG. 2 shows another embodiment of a second flow path within a split airflow system. [Figure 3] Figure 3 shows the cooling effect of different airflows on different heating elements. [Figure 4] FIG. 4 shows the temperature curves of a heating element powered in different ways. [Figure 5] Figure 5 shows the temperature curve at the mouthpiece exit. [Figure 6] Figure 6 shows the average vapor saturation curve at the mouthpiece exit. [Figure 7] Figure 7 shows the droplet diameter ratio at the mouthpiece exit for the total and separated airflow configurations. [Figure 8] Figures 8a to 8f show heating elements that may be used in smoking systems according to the present invention. [Figure 9]9a and 9b are detailed views of the filaments of the heating element, showing the meniscus of the liquid aerosol-forming substrate between the filaments (FIG. 9a) and the capillary material extending between the filaments (FIG. 9b). [Figure 10] Figure 10 shows a cross section of a cartridge system with a high retention-release material (HRM) and an air passage within the HRM. [Figure 11] Figure 11 shows a cross section of an alternative cartridge system with a high retention-release material (HRM) and an air passage within the cartridge. [Figure 12] FIG. 12 shows an exploded view of the cartridge system of FIG. [Figure 13] FIG. 13 shows a cross section of a cartridge system with liquid and air passages through the liquid. DETAILED DESCRIPTION OF THE INVENTION

[0067] FIG. 1 illustrates an embodiment of a cartridge 4 and mouthpiece 1 for an aerosol-generating smoking system. An elongated main housing 5 houses the cartridge with a tubular cartridge housing 4 containing an aerosol-forming substrate, e.g., a liquid-containing capillary material 41. The cartridge housing has an open proximal end 42. A heater 30, preferably a substantially planar mesh heater, is positioned over the open proximal end of the cartridge housing 4. The heating element may or may not be in direct physical contact with the aerosol-forming substrate 41. A mouthpiece 1 having a substantially tubular elongated body 15 is aligned with the main housing, cartridge housing 4, and heating element 30. The elongated body 15 has an open distal end facing the heater 30.

[0068] The embodiment shown in FIG. 1 includes a second channel 10 defining a second flow path within the mouthpiece 1, directing second ambient air 20 entering over the heater 30 to an exhaust port 12 at the proximal or oral end of the mouthpiece 1, where the consumer takes a puff. Also disposed within the mouthpiece 1 is a first channel 11 defining a first flow path. First ambient air 21 enters the first channel 11 through a first inlet 110 and is directed directly to the outlet 12 without passing through the heater 30. This first airflow 21 merges with the second airflow 20 within the second channel 10 at a location 111 downstream of the heater 30 and upstream of the outlet 12. The most downstream portion of the second channel 10 is identical to the first channel 11. The second airflow 20 passes through the heater 30, where an aerosol is formed from the aerosol-forming substrate 41 by heating and vaporizing the liquid, and the aerosol is entrained in the second airflow 21. The second air flow carrying the aerosol meets the first air flow 21 at location 111. The first air flow 21 mixes with the second air flow carrying the aerosol and is cooled.

[0069] Both the second inlet 100 and the first inlet 110 are openings or perforations in the mouthpiece 1, located halfway distally of the elongated body 15 of the mouthpiece 1. A second flow path in the upstream second channel portion 101 flows through the elongated body parallel to the periphery of the elongated body to the proximal end of the mouthpiece. In the radially inwardly directed portion 102 of the second channel 10, the second airflow 20 is directed toward the center of the elongated body, and in the centrally located portion 103 of the second channel, the second airflow 20 is directed toward the heater 30, impinging on the central portion 31 of the heater 30. The second airflow 20 passes over the heater 30 and diffuses radially outward to several longitudinal ends 104 of the second channel 10. The longitudinal ends 104 are regularly spaced along the periphery within the elongated body.

[0070] In this embodiment, the first and second flow paths and the first and second channels, respectively, are located entirely within the mouthpiece 1 of the aerosol generation system.

[0071] FIG. 2 illustrates an embodiment of the cartridge 4 with a heater 30 located at the bottom of the cartridge and covering the open distal end 43 of the cartridge housing 41. A second inlet 100 is located within the main housing 5, and ambient air enters the radially inwardly oriented portion 102 of the second channel and is directed directly to the center of the main housing. In the centrally located portion 103 of the second channel, the air is directed perpendicular to the heater 30. The air then passes through the heater 30 and entrains the aerosol generated by the heater 30 heating the liquid in the aerosol-forming substrate 40. The aerosol-laden air is directed to the proximal end of the cartridge 4 within several longitudinal portions 105 of the second channel 10 located between and along the cartridge housing 41 and the main housing 5. There, the aerosol-laden second air stream is directed to enter and exit through a single centrally located opening 52 in the main housing 5. A mouthpiece (not shown) may be located adjacent to the main housing. The mouthpiece, in turn, preferably also has a centrally located opening and an end 104 of a second channel 10 for receiving the second airflow containing the aerosol and directing it to a single exit opening 12 in the proximal end of the mouthpiece 1. In such an embodiment, the first channel 11 may be essentially similar to the embodiment shown in Figure 1. The first channel may be a separate channel within the mouthpiece, or may comprise radial holes extending into a second channel within the mouthpiece such that the first airflow 21 merges with the second airflow within the mouthpiece.

[0072] The data shown in Figure 3 demonstrate that increasing the air flow rate through the mesh heater increases its cooling effectiveness. Cooling rates were measured using different mesh heaters: Reking (45 micrometers / 180 per inch), Haver (25 micrometers / 200 per inch), and a three-strip Warrington (25 micrometers / 250 per inch). Measurement data for the Reking heater is shown with crosshairs, for the Haver heater with circles, and for the three-strip Warrington heater with triangles. All heaters were operated at 3 watts. Temperature was measured with a thermocouple coupled to the heater. Increasing the air flow rate, displayed on the x-axis in liters per minute (L / min), resulted in a decrease in the temperature measured for the mesh heater. The typical size of the airflow in an aerosol-generating system can approximate standard smoking techniques, such as the Health Canada smoking technique, that result in significant cooling of the heater. The exemplary smoking technique, such as Health Canada's, involves drawing 55 ml of the above mixture with air over a two-second period. The alternative method is to draw 55 ml over 3 seconds. Neither exemplary smoking method can exactly mimic the behavior, but they serve as a proxy for what the average user draws.

[0073] Experiments with the split-airflow system were preferably conducted with a first airflow that was 6 / 7 to 8 / 9 of the total volume of ambient air. Therefore, the volume of ambient air directed to the heater was 1 / 7 to 1 / 9 of the total volume of ambient air. Therefore, approximately 85 to 89 percent of the total volume of ambient air was conveyed directly through the mouthpiece outlet, and only approximately 11 to 15 percent of the total volume of the airflow passed through the heater.

[0074] Exemplary values ​​for channels such as those shown in the embodiment of FIG. 1 are as follows:

[0075] Second channel air inlet: diameter 0.75 mm and total channel cross section 0.44 square mm.

[0076] First channel air inlet: 4 x 1 mm diameter, and total channel cross section 3.14 square mm.

[0077] The graph in Figure 4 shows the average heater temperature versus time during one puff. Curve 60 represents the baseline temperature data for the heater, where all of the airflow is directed to the heater. Curve 70 represents the temperature data for the heater in a split airflow system, where only 1 / 7 of the total airflow is directed to the heater. For the baseline data, the heater was heated at 5 watts, while the heater receiving the lesser airflow was heated at 4 watts. It can be seen that with split airflow, 1 watt of energy can be saved over the length of one puff.

[0078] FIG. 5 shows the effect of split airflow on the temperature of the aerosol-carrying airflow at the mouthpiece exit during a single puff. These data refer to a mouthpiece embodiment in which a first airflow merges with a second aerosol-carrying airflow within the mouthpiece, as shown in FIG. 1. Temperature curve 61 represents the outlet air temperature for a heater powered at 5 watts, with the entire airflow hitting the heater. Temperature curve 71 represents the outlet air temperature for a heater powered at 4 watts, with only 1 / 7 of the total airflow directed at the heater. By combining 6 / 7 of the amount of "fresh" air with the aerosol stream, the temperature of the aerosol-carrying airflow at the mouthpiece exit is significantly lower. Typically, the "fresh" air mixed into the aerosol-carrying airflow is at room temperature.

[0079] Significant differences can also be observed in the ratio of vapor pressure at the mouthpiece exit to the saturation pressure of the glycerol solution (P / P) during a single puff. This ratio is shown in FIG. 6. Curve 72 represents the pressure data at the exit for a heater powered at 4 watts in a split-airflow system, with 1 / 7 of the total airflow directed to the heater. Curve 62 represents the pressure data at the exit for a heater powered at 5 watts, with the total airflow impinging on the heater. The pressure ratio is higher for the split-airflow embodiment due to the cooling effect. This represents a greater degree of supersaturation of the glycerol solution, favoring the aerosolization of smaller droplets. Simulations clearly predict smaller droplet sizes for the cooler vapor of the split-airflow embodiment compared to the vapor of the non-split or full-airflow embodiment. These simulation data 67 are shown in FIG. 7 for a single puff at the mouthpiece exit. The Y-axis represents the droplet diameter ratio for the split-airflow to total airflow system. This ratio is calculated and expressed as d_split / d_ref=T*Ln(S)ref / T*Ln(S)split versus time (in seconds) during one puff of the aerosol generating system, where T is the temperature in degrees Kelvin and S is the ratio of Pv and P ∞ is the saturation ratio, which is a function of (T).

[0080] FIG. 8a illustrates a first heating element 30. The heating element includes a mesh 36 formed from 304L stainless steel with a mesh size of approximately 400 mesh US (approximately 400 filaments per inch). The filaments have a diameter of approximately 16 micrometers. The mesh is connected to electrical contacts 32 separated from each other by gaps 33 and formed of copper foil with a thickness of approximately 30 micrometers. The electrical contacts 32 are provided on a polyimide substrate 34 with a thickness of approximately 120 micrometers. The filaments forming the mesh define gaps between them. In this example, the gaps have a width of approximately 37 micrometers, although larger or smaller gaps may be used. Using a mesh of these approximate dimensions allows a meniscus of the aerosol-forming substrate to form within the gaps, and the mesh of the heating element draws the aerosol-forming substrate through capillary action. The ratio of the open area of ​​the mesh, i.e., the area of ​​the gaps to the total area of ​​the mesh, is advantageously between 25 percent and 56 percent. The total resistance of the heating element is approximately 1 ohm. The mesh provides the majority of this resistance, as most of the heat is generated by the mesh, which in this example has an electrical resistance over 100 times higher than the electrical contacts 32.

[0081] The substrate 34 is electrically insulating and, in this example, is formed from a polyimide sheet having a thickness of about 120 micrometers. The substrate is circular and has a diameter of 8 millimeters. The mesh is rectangular and has side lengths of 5 millimeters and 2 millimeters. These dimensions allow for the production of a complete system having a size and shape similar to that of a conventional cigarette or cigar. Another example of dimensions that has proven effective is a circular substrate with a diameter of 5 millimeters and a rectangular mesh of 1 millimeter by 4 millimeters.

[0082] Figures 8b and 8c illustrate other alternative heating elements. In the heating element of Figure 8b, the filament 37 is bonded directly to the substrate 34, and therefore the contacts 32 are bonded to the filament. The contacts 32 are again separated from each other by insulating gaps 33 and are formed from copper foil about 30 micrometers thick. The same arrangement of substrate filaments and contacts can also be used for mesh-type heaters, as shown in Figure 8a. Having the contacts as the outermost layer can be beneficial in providing reliable electrical contact with the power source.

[0083] The heating element of Figure 8c includes multiple heater filaments 38 integrally formed with electrical contacts 39. Both the filaments and electrical contacts are formed from stainless steel foil that has been etched to define the filaments 38. The contacts 39 are separated by gaps 33 except when connected by the filaments 38. The stainless steel foil is provided on a polyimide substrate 34. Again, the filaments 38 provide the majority of the resistance, so that the majority of the heat is generated by the filaments. In this example, the filaments 38 have an electrical resistance that is over 100 times higher than the electrical contacts 39.

[0084] Figures 8d-8e show several heating elements with a mesh 36 fixed to and between two contact portions 35. The mesh is fixed to either side of the contact portion 35. Each contact portion has a rounded outer periphery and two openings 351. The heating element 30 may be attached to a cartridge housing or to a supporting base via these openings 351, for example by screws.

[0085] The capillary material 41 is advantageously oriented within the housing 4 to transport the liquid to the heating element 30. When the cartridge is assembled, the heater filaments 36, 37, 38 can be in contact with the capillary material 41, and the aerosol-forming substrate can be directly transported to the mesh heater. Figure 9a is a detailed view of the heating element filaments 36, showing the meniscus 46 of the liquid aerosol-forming substrate between the heater filaments 36. It can be seen that the aerosol-forming substrate contacts most of the surface of each filament, such that most of the heat generated by the heating element enters directly into the aerosol-forming substrate.

[0086] 9b is a detailed view, similar to FIG. 9a, illustrating an example of capillary material 41 extending into the gaps between filaments 36. Capillary material 41 may be capillary material positioned adjacent to or in contact with a heating element, and preferably has high temperature resistance. It can be seen that by providing capillary material comprising fine thread fibers extending into the gaps between filaments 36, liquid delivery to the filaments can be ensured.

[0087] In use, the heating elements may operate by resistive heating. Electrical current is passed through the filaments 36, 37, 38 under the control of control electronics (not shown), heating the filaments to 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), so that the elevated temperature is localized to the filaments. The system may be configured to generate heat by supplying electrical current to the heating elements in response to a user's puff, or may be configured to generate heat continuously while the device is in the "on" state.

[0088] Different materials for the filament may be appropriate for different systems. For example, in a continuous heating system, a graphite filament may be appropriate because it has a relatively low specific heat capacity and is compatible with low current heating. In a smoke-operated system where heat is generated in short bursts using high current pulses, a stainless steel filament with a high specific heat capacity may be more appropriate.

[0089] 10, a cross section of a cartridge system is shown in which a second flow path includes airflow directed through the cartridge. A fluid-permeable heater, e.g., a mesh heater 30, is provided over the open top end of the housing 4. To seal the top of the housing 4, a sealing layer 48, e.g., a polymer layer, is provided between the upper rim of the housing 4 and the heater 30. Additionally, a sealing disk 47, e.g., a polymer disk, is provided on the upper side of the heater 30. The sealing disk 47 can be used to control the airflow through the heater, particularly to provide a restriction to the airflow. A sealing disk can also be located on the bottom side of the heater 30.

[0090] The cartridge housing 4 contains a liquid containing high retention or high release material (HRM) 41, which serves as a liquid reservoir and directs the liquid to the heater 30 for evaporation therein. A capillary disk 44, e.g., a fiber disk, is positioned 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. The capillary disk is kept wet by the aerosol-forming liquid of the HRM to ensure a supply of liquid for evaporation when the heater is activated.

[0091] The housing 4 is provided with an air permeable bottom 45. The air permeable bottom is provided with an air flow inlet 450. The air flow inlet 450 allows air to flow into the housing through the bottom 45, and only in this direction. Air or liquid cannot exit the housing through the air permeable bottom 45. The air permeable bottom 45 may, for example, comprise a semi-permeable membrane as the air flow inlet 450, or may be a bottom cover that includes one or more one-way valves, as described below.

[0092] When the heater has a low depression in its side, as occurs during smoking, air can pass into the cartridge through airflow inlet 450. Airflow 20 passes through HRM 41 and then through heater 30. Airflow 20 containing the aerosol then flows to the downstream end of the aerosol-generating device, preferably into a channel located in the center of the mouthpiece.

[0093] The side walls of the housing 4 may also be provided with lateral air permeable portions 46 to provide lateral air flow into the housing. The lateral air permeable portions 46 may be designed as air flow inlets 450 in the air permeable bottom 45.

[0094] In Figure 11, the layout and function of the cartridge system is essentially the same as that shown in Figure 10. However, the HRM 41 is provided with a central opening 412. Air entering the airflow inlet 450 in the bottom 45 of the housing passes through the central opening 412. Airflow passes laterally through the HRM within the cartridge. Optional lateral air permeable sections 46 in the side walls of the housing 4 can provide lateral airflow through the HRM 41.

[0095] Figure 12 shows an exploded view of the cartridge system shown in Figure 11. A ring-shaped tubular HRM 41 is provided within the housing 4. The bottom 45 of the housing is a disk that includes a one-way valve 49 located in the center of the disk and is aligned with a central opening 412 within the HRM 41. Such a one-way valve may be a commercially available valve, such as those used in medical devices or baby bottles.

[0096] 13 is a cross-section of another embodiment of the cartridge system. The same reference numbers are used for the same or similar elements. In this embodiment, the housing 4 is filled with an aerosol-forming liquid 411. The housing may be made of metal, a plastic material (e.g., a polymeric material), or glass. The valve 49 may be attached directly to the bottom 45 of the housing. The bottom 45 may be provided with a recess for airtight assembly with the valve. The valve is preferably made of a flexible material so that airtight assembly with the bottom material can be achieved.

[0097] In the above cartridge systems illustrated in Figures 10 to 13, the cartridge housing 4 may be a separate cartridge container in addition to the cartridge housing illustrated in Figure 1, for example. In particular, the liquid containing cartridge 411 may be a pre-manufactured product and may be inserted into a cartridge housing provided in the aerosol generation system to receive the pre-manufactured cartridge.

[0098] 1. A split airflow system for an electrically heated smoking system for generating aerosols, said split airflow system having a downstream end, said airflow system comprising: a first channel defining a first flow path; a second channel defining a second flow path; the first flow path directs ambient air from outside the system to the downstream end of the system; and the second flow path directs the ambient air from outside the system toward a substantially planar fluid-permeable heating element before conveying the ambient air to the downstream end; and a split airflow system, wherein the first channel and the second channel define a total volume of ambient air passing through the system, and the first channel provides at least 50 percent of the total volume of ambient air passing through the system. 2. The split airflow system of 1, wherein the heating element is a heating element with multiple conductive filaments, such as a mesh heating element. 3. A split airflow system as described in any one of 1 to 2, wherein the first channel supplies about 65 percent to about 95 percent, preferably about 85 percent to about 89 percent, of the total volume of ambient air passing through the system. 4. The split airflow system of any of 1-3, wherein the first channel merges with an end of the second channel such that the first flowpath merges with the second flowpath after the second flowpath directs ambient air past the heating element. 5. A split airflow system as described in any one of 1 to 3, wherein the first channel and the second channel form distinct channels such that the first flow path and the second flow path mutually direct ambient air from outside the system to the downstream end of the system separated from each other. 6. The split airflow system of any of 1-5, wherein at least a portion of the second channel and the heating element are positioned perpendicular to one another such that the at least a portion of the second channel directs ambient air to impinge on the heating element at a right angle. 7. A split airflow system according to any one of 1 to 6, wherein at least a portion of the second channel located downstream of the heating element is located around the heating element. 8. A method of directing airflow in an electrically heated smoking system for generating an aerosol, said method comprising: - directing ambient air from outside the system to a downstream end of the system along a first flow path; - directing the ambient air from outside the system toward a substantially planar fluid-permeable heating element before conveying the ambient air along a second flow path to the downstream end of the system; wherein a total volume of ambient air passing through the system passes along the first flow path and along the second flow path, and wherein at least 50 percent of the total volume of ambient air passing through the system passes along the first flow path. 9. The method of claim 8, further comprising the step of combining the ambient air in the first flow path and the ambient air in the second flow path before they reach the downstream end of the system. 10. The method of claim 8, further comprising maintaining the first flow path separated from the second flow path. 11. The method of any of 8 to 10, comprising the step of directing the ambient air in the second flow path so that the ambient air in the second flow path impinges substantially perpendicularly on the heating element. 12. Providing a liquid aerosol-forming substrate; heating the heating element, thereby vaporizing liquid from the aerosol-forming substrate to form an aerosol; 12. The method of any one of claims 8 to 11, further comprising the step of capturing the formed aerosol in the ambient air directed toward the heating element by the second flow path before the ambient air containing the aerosol is conveyed to the downstream end of the system. 13. providing at least a portion of the first channel and at least a portion of the second channel within a mouthpiece of the system, the downstream end of the system being a proximal end of the mouthpiece; directing ambient air within the at least a portion of the second channel in a direction along a length of the mouthpiece toward the proximal end of the mouthpiece; reversing the direction of the ambient air in the second channel; 13. The method according to any one of 8 to 12, further comprising the step of guiding the ambient air toward the heating element so that the ambient air hits the heating element. 14. The method of claim 13, further comprising directing the ambient air within the at least a portion of the second channel along a central axis of the mouthpiece to substantially center the ambient air relative to the heating element. 15. An electrically heated smoking system for generating aerosols, comprising the split airflow system according to any one of 1 to 7, wherein the smoking system: a reservoir portion comprising a housing for holding a liquid aerosol-forming substrate, said housing having an open end; a substantially planar fluid-permeable heating element extending across the open end of the housing; a mouthpiece disposed adjacent to the housing, the mouthpiece including an elongated body including an open distal end, the open distal end facing the housing; the mouthpiece further comprising: a first channel including a first inlet opening disposed in a sidewall of the elongate body for defining a first flow path for directing ambient air from outside the system through the mouthpiece to the outlet opening, and an outlet opening disposed at a proximal end of the elongate body; an end of a second channel extending between the open distal end of the elongate body and the proximal end of the elongate body, the second channel is disposed within the smoking system and defines a second flow path; the second flow path directs ambient air entering the smoking system toward the heating element, where it is capable of capturing aerosols generated by the ambient air vaporizing a liquid due to heating by the heating element before carrying the aerosol-laden ambient air to the proximal end of the elongated body of the mouthpiece; A smoking system, wherein the first channel and the second channel define a total volume of ambient air passing through the smoking system, and the first channel supplies at least 50 percent of the total volume of ambient air passing through the smoking system. 16. A smoking system as described in 15, wherein the first channel merges with the end of the second channel downstream of the open distal end of the elongate body. 17. The smoking system described in 15, wherein the second channel includes a second outlet opening disposed at the proximal end of the elongate body, the second outlet opening being separate from the outlet opening of the first channel. 18. A smoking system as described in any one of 15 to 17, wherein the second inlet opening of the second channel is located within the side wall of the elongated body. 19. A smoking system described in any of 15 to 18, wherein the second channel is arranged downstream of the heating element and includes at least one second channel portion that carries ambient air containing the aerosol, and the at least one second channel portion is arranged longitudinally along the periphery of the housing or the mouthpiece. 20. A smoking system as described in 19, wherein the second channel includes a plurality of second channel ends arranged longitudinally along the periphery of the elongate body. 21. A smoking system described in any one of 15 to 20, wherein the substantially planar fluid-permeable heating element comprises a plurality of conductive filaments.

[0099] 22. A split airflow system for an electrically heated smoking system for generating aerosols, the split airflow system having a downstream end, the airflow system comprising: a first channel defining a first flow path; a second channel defining a second flow path; the first flow path directs ambient air from outside the system to the downstream end of the system; and the second flow path directs the ambient air from outside the system toward a substantially planar fluid-permeable heating element before conveying the ambient air to the downstream end of the system; the first channel and the second channel define a total volume of ambient air passing through the system, and the first channel provides at least 50 percent of the total volume of ambient air passing through the system; and at least a portion of the second channel and the heating element are disposed perpendicular to one another such that the at least a portion of the second channel directs ambient air to impinge on the heating element perpendicularly; and at least a portion of the second channels disposed downstream of the substantially planar fluid-permeable heating element are disposed about the periphery of the substantially planar fluid-permeable heating element so as to direct ambient air containing aerosol from a center of the substantially planar fluid-permeable heating element radially outward relative to the periphery of the substantially planar fluid-permeable heating element toward the at least a portion of the second channels disposed about the periphery of the substantially planar fluid-permeable heating element; at least a portion of the first channel and at least a portion of the second channel are provided within a mouthpiece of the system, and the downstream end of the system is a proximal end of the mouthpiece; Ambient air within the at least a portion of the second channel is directed along a length of the mouthpiece toward the proximal end of the mouthpiece; a reversal of direction of the ambient air in the second channel is performed; A split airflow system in which the ambient air is directed toward the heating element to impinge on the heating element. 23. The split airflow system of claim 22, wherein the heating element is a heating element having multiple conductive filaments, such as a mesh heating element. 24. A split airflow system as described in any of 22 to 23, wherein the first channel supplies between about 65 percent and about 95 percent, preferably between about 85 percent and about 89 percent, of the total volume of ambient air passing through the system. 25. The split airflow system of any of 22-24, wherein the first channel merges with an end of the second channel such that the first flowpath merges with the second flowpath after the second flowpath directs ambient air past the heating element. 26. A split airflow system as described in any one of 22 to 24, wherein the first channel and the second channel form distinct channels such that the first flow path and the second flow path mutually direct ambient air from outside the system to the downstream end of the system separated from each other. 27. A method of directing airflow in an electrically heated smoking system for generating an aerosol, said method comprising: - directing ambient air from outside the system to a downstream end of the system along a first flow path; - directing ambient air from outside the system toward a substantially planar fluid-permeable heating element before conveying the ambient air along a second flow path to the downstream end of the system; wherein a total volume of ambient air passing through the system passes along the first flow path and along the second flow path, and at least 50 percent of the total volume of ambient air passing through the system passes along the first flow path. directing the ambient air within the second flow path such that the ambient air within the second flow path impinges substantially perpendicularly on the substantially planar fluid-permeable heating element; - directing the aerosol-laden ambient air from the center of the heating element radially outward toward the periphery of the heating element and downstream of the periphery toward an outlet opening; Including, providing at least a portion of the first channel and at least a portion of the second channel within a mouthpiece of the system, the downstream end of the system being a proximal end of the mouthpiece; directing ambient air within the at least a portion of the second channel in a direction along a length of the mouthpiece toward the proximal end of the mouthpiece; reversing the direction of the ambient air in the second channel; directing the ambient air toward the heating element to strike the heating element; The method further comprises: 28. The method of claim 27, further comprising the step of combining the ambient air in the first flow path and the ambient air in the second flow path before they reach the downstream end of the system. 29. The method of claim 27, further comprising maintaining the first flow path separated from the second flow path. 30. Providing a liquid aerosol-forming substrate; heating the heating element, thereby vaporizing liquid from the aerosol-forming substrate to form an aerosol; 30. The method of any of claims 27 to 29, further comprising the step of: capturing the formed aerosol in the ambient air directed toward the heating element by the second flow path before the ambient air containing the aerosol is conveyed to the downstream end of the system. 31. The method of claim 30, further comprising directing the ambient air within the at least a portion of the second channel along a central axis of the mouthpiece to substantially center the ambient air relative to the heating element. 32. An electrically heated smoking system for generating aerosols, comprising the split airflow system according to any one of 22 to 26, wherein the smoking system: a reservoir portion comprising a housing for holding a liquid aerosol-forming substrate, said housing having an open end; a substantially planar fluid-permeable heating element extending across the open end of the housing; a mouthpiece disposed adjacent to the housing, the mouthpiece including an elongated body including an open distal end, the open distal end facing the housing; The mouthpiece, the first channel including a first inlet opening disposed in a sidewall of the elongate body for defining the first flow path that directs ambient air from outside the system through the mouthpiece to an outlet opening, the outlet opening being disposed at a proximal end of the elongate body; an end of the second channel extending between the open distal end of the elongate body and the proximal end of the elongate body, the second channel is disposed within the smoking system and defines a second flow path; the second flow path directs ambient air entering the smoking system toward the heating element, where it is capable of capturing aerosols generated by the ambient air vaporizing a liquid due to heating by the heating element before carrying the aerosol-laden ambient air to the proximal end of the elongated body of the mouthpiece; the first channel and the second channel define a total volume of ambient air passing through the smoking system, the first channel providing at least 50 percent of the total volume of ambient air passing through the smoking system; A smoking system wherein the second channel is positioned downstream of the heating element and includes at least one second channel portion that carries ambient air containing the aerosol, and the at least one second channel portion is positioned longitudinally along the periphery of the housing or the mouthpiece. 33. The smoking system of claim 32, wherein the first channel merges with the end of the second channel downstream of the open distal end of the elongate body. 34. The smoking system described in 32, wherein the second channel includes a second outlet opening disposed at the proximal end of the elongate body, the second outlet opening being separate from the outlet opening of the first channel. 35. A smoking system described in any one of 32 to 34, wherein the second inlet opening of the second channel is located within the side wall of the elongated body. 36. A smoking system described in any one of 32 to 35, wherein the second channel includes a plurality of second channel ends arranged longitudinally along the periphery of the elongate body. 37. A smoking system described in any one of 32 to 36, wherein the substantially planar fluid-permeable heating element comprises a plurality of conductive filaments.

Claims

1. 1. An aerosol generation system comprising a split airflow system having a downstream end, the airflow system comprising: a first channel defining a first flow path; a second channel defining a second flow path; Equipped with the first flow path directs ambient air from outside the split airflow system to the downstream end of the split airflow system; the second flow path directs the ambient air from outside the split airflow system toward a substantially planar fluid-permeable heating element before conveying the ambient air to the downstream end; and in use, the ambient air in the first channel is cooler than the ambient air carrying the aerosol in the second channel, resulting in supersaturated air being provided at the downstream end of the split airflow system. system.

2. 2. The aerosol generation system of claim 1, wherein the total number of air inlets in both the first channel and the second channel is between 2 and 10.

3. 3. The aerosol-generating system of claim 1 or 2, comprising an aerosol-forming substrate of plant origin.

4. A method of generating an aerosol, comprising using the aerosol generating system according to any one of claims 1 to 3.

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