Clothes dryer and clothes drying method

Abstract

The invention relates to the field of household appliances, particularly provides a clothes dryer and a clothes drying method, and aims to solve the problem of low clothes drying efficiency caused by the fact that the working efficiency of an evaporator and a condenser cannot be considered at the same time in the prior art. In order to achieve the purpose, the clothes dryer comprises a drying chamber, an evaporator and a condenser and further comprises a pre-cooling heat exchanger, the pre-cooling heat exchanger comprises a pre-cooling channel and a first external channel which are not communicated with each other, and external air enters the first external channel to primarily cool air in the pre-cooling channel; the preheating heat exchanger comprises a preheating channel and a second external channel which are not communicated with each other, and external air enters the second external channel to primarily heat the air in the preheating channel; the drying chamber, the precooling channel, the evaporator, the preheating channel and the condenser sequentially form a circulating air duct; external air sequentially enters the first external channel and the second external channel. The working efficiency of the evaporator and the working efficiency of the condenser can be improved at the same time, and the drying speed of the clothes dryer is greatly increased.

Description

Technical Field

[0001] The present invention relates to the field of household appliances, and in particular provides a clothes dryer and a clothes drying method. Background Art

[0002] In the existing traditional clothes dryer heat pump system, when the internal air circulates, the air passes through the drying chamber to dry the items, then passes through the evaporator in the heat pump system for dehumidification, and then passes through the condenser in the heat pump system for air heating. After becoming dry air, it enters the drying chamber to form an air circuit circulation.

[0003] In traditional heat pump dryer systems, the dehumidification airflow is an internal circulation system. The ideal drying effect is to keep the air temperature as low as possible after the evaporator dehumidifies and as high as possible after the condenser heats the clothes. This significantly increases the drying speed. For heat pump systems, this requires a high condensing temperature and a low evaporating temperature. Since the heat pump system's airflow is a closed loop, it can't fully exchange heat with the environment. As a result, the heat for both condensation and evaporation in the heat pump system comes mostly from the internally circulating air. Thus, if the air entering the evaporator is low, the dehumidification effect is good, but the condenser outlet air temperature is low, resulting in poor drying results. If the air entering the evaporator is high, even though the condenser outlet air temperature is high, the dehumidification efficiency is poor. Therefore, existing dryers cannot balance drying temperature and dehumidification effectiveness, limiting drying speed and preventing a significant increase in drying speed.

[0004] Accordingly, this field requires a new technical solution to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problem, namely, to solve the problem in the prior art that the working efficiency of the evaporator and the condenser cannot be taken into account at the same time, resulting in low drying efficiency. To this end, the present invention provides a clothes dryer, which includes: a drying chamber for placing items to be dried; an evaporator, which is arranged at the air outlet of the drying chamber; a condenser, which is arranged on the air outlet side of the evaporator; a precooling heat exchanger, which includes a precooling channel and a first external channel that are not connected to each other, and the outside air enters the first external channel to initially cool the air in the precooling channel; a preheating heat exchanger, which includes a preheating channel and a second external channel that are not connected to each other, and the outside air enters the second external channel to initially heat the air in the preheating channel; the drying chamber, the precooling channel, the evaporator, the preheating channel, and the condenser constitute a circulating air duct in sequence; and the outside air enters the first external channel and the second external channel in sequence.

[0006] In the above embodiment of the clothes dryer, the pre-cooling channel and the first external channel are separated by a first substrate; the pre-heating channel and the second external channel are separated by a second substrate.

[0007] In the above embodiment of the clothes dryer, pre-cooling inner fins and pre-cooling outer fins are provided on the first substrate, the pre-cooling inner fins are located in the pre-cooling channel, and the pre-cooling outer fins are located in the first external channel.

[0008] In the above embodiment of the clothes dryer, preheating inner fins and preheating outer fins are provided on the second substrate. The preheating inner fins are located in the preheating channel, and the preheating outer fins are located in the second external channel.

[0009] In the above embodiment of the clothes dryer, the first substrate is connected to the second substrate.

[0010] In the above embodiment of the clothes dryer, a third substrate is provided between the first substrate and the second substrate, and the third substrate is used to isolate heat transfer between the first substrate and the second substrate.

[0011] In the above embodiment with the clothes dryer, a fan is provided on the second external channel.

[0012] In the above embodiment of the clothes dryer, both the first substrate and the second substrate are metal substrates.

[0013] A clothes drying method, wherein the clothes drying method uses any of the above-mentioned clothes dryers, and the clothes drying method includes: obtaining the temperature of the air flowing out of the drying chamber; comparing it with a first preset temperature value; and selecting to turn on the pre-cooling heat exchanger or not to turn on the pre-cooling heat exchanger according to the comparison result.

[0014] In the above-mentioned specific embodiment of the drying method, the drying method further includes: obtaining the temperature of the air flowing out of the evaporator; comparing it with a second preset temperature value; and selecting whether to turn on the preheating heat exchanger or not according to the comparison result.

[0015] Under the above technical solution, in order to solve the problem that the dryer in the prior art cannot balance the working efficiency of the evaporator and condenser, resulting in low drying efficiency, the present invention provides a pre-cooling heat exchanger and a pre-heating heat exchanger. The high-temperature and high-humidity gas in the drying chamber first enters the pre-cooling channel of the pre-cooling heat exchanger. When the pre-cooling heat exchanger is in an operating state, the high-temperature and high-humidity gas is initially cooled in the pre-cooling channel by the outside air in the first outside channel. The air after the initial cooling enters the evaporator for dehumidification. In this way, under the same evaporator heat exchange rate, the evaporation temperature of the dryer heat pump system can be further reduced, thereby improving the dehumidification capacity of the dryer. After flowing out of the evaporator, the air enters the pre-heating channel of the pre-heating heat exchanger. When the pre-heating heat exchanger is in an operating state, the air in the pre-heating channel is initially heated by the outside air in the second outside channel. The air after the initial heating enters the condenser for heating. This can reduce the heat load of the condenser and improve the working efficiency of the condenser. The air after passing through the condenser becomes high-temperature and low-humidity air, and then flows into the drying chamber to dry the clothes.

[0016] This solution simultaneously improves the efficiency of both the evaporator and condenser, balancing drying temperature and dehumidification, significantly increasing the dryer's drying speed. Furthermore, cooling the dryer through outside air reduces costs and requires no additional processing or cooling media, nor does it require complex piping, pumps, or other liquid handling equipment. This simplicity results in greater reliability and ease of maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0018] Figure 1 1 is a schematic diagram of the principle of the first embodiment of the clothes dryer in the present invention;

[0019] Figure 2 This is a schematic diagram of the principle of the second embodiment of the clothes dryer in the present invention;

[0020] Figure 3 Schematic diagram of the structure of the pre-cooling heat exchanger and the pre-heating heat exchanger in the present invention;

[0021] Figure 4 It is a flow chart of the main steps of the clothes drying method in the present invention.

[0022] In the figure: 1. Drying chamber, 2. Evaporator, 3. Condenser, 4. Precooling heat exchanger, 401. Precooling channel, 402. First external channel, 403. First substrate, 404. Precooling inner fins, 405. Precooling outer fins, 5. Preheating heat exchanger, 501. Preheating channel, 502. Second external channel, 503. Second substrate, 504. Preheating inner fins, 505. Preheating outer fins, 6. Third substrate, 7. Fan. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific applications. For example, although the description is combined with a clothes dryer, this is not restrictive, and those skilled in the art can apply the present invention to other scenarios requiring the use of an evaporator and a condenser as needed.

[0024] It should be noted that, in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. These are used solely for ease of description and are not intended to indicate or imply that the relevant devices or components must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, ordinal numbers such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted" and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; and direct or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] Furthermore, in order to more clearly demonstrate the core technical solution of the present invention, the description of the well-known structures of the dryer is omitted in the following description. However, this omission is only for the convenience of description and does not mean that the dryer can be without these structures.

[0027] Example 1

[0028] like Figure 1As shown, the present invention proposes a clothes dryer, comprising: a drying chamber 1 for placing articles to be dried; an evaporator 2, which is arranged on the air outlet side of the drying chamber 1 and is used to dehumidify the gas flowing out of the drying chamber 1; a condenser 3, which is arranged on the air outlet side of the evaporator 2 and is used to heat the gas flowing out of the evaporator 2; a precooling heat exchanger 4, which includes a precooling channel 401 and a first external channel 402 that are not connected to each other, and the outside air enters the first external channel 402 to initially cool the air in the precooling channel 401; a preheating heat exchanger 5, which includes a preheating channel 501 and a second external channel 502 that are not connected to each other, and the outside air enters the second external channel 502 to initially heat the air in the preheating channel 501; the drying chamber 1, the precooling channel 401, the evaporator 2, the preheating channel 501, and the condenser 3 sequentially form a circulating air duct.

[0029] In this embodiment, in order to solve the problem that the dryer in the prior art cannot take into account the working efficiency of the evaporator and the condenser, resulting in low drying efficiency, a pre-cooling heat exchanger 4 and a pre-heating heat exchanger 5 are set. The high-temperature and high-humidity gas in the drying chamber 1 first enters the pre-cooling channel 401 in the pre-cooling heat exchanger 4. When the pre-cooling heat exchanger 4 is in the working state, the high-temperature and high-humidity gas is initially cooled in the pre-cooling channel 401 by the outside air in the first outside channel 402. The air after the initial cooling enters the evaporator 2 for dehumidification. In this way, under the same heat exchange capacity of the evaporator 2, the heat pump system of the dryer is improved. The evaporation temperature of the system can be further reduced, thereby improving the dehumidification capacity of the clothes dryer; after the air flows out of the evaporator 2, it enters the preheating channel 501 in the preheating heat exchanger 5. When the preheating heat exchanger 5 is in working state, the air in the preheating channel 501 is initially heated by the outside air in the second outside channel 502, and the air after the initial heating enters the condenser 3 for heating, which can reduce the heat load of the condenser 3 and improve the working efficiency of the condenser 3; the air after passing through the condenser 3 becomes high-temperature and low-humidity air, and then flows into the drying chamber 1 to dry the clothes.

[0030] This solution simultaneously improves the working efficiency of the evaporator 2 and the condenser 3, taking into account both the drying temperature and the dehumidification effect, significantly increasing the drying speed of the dryer. In addition, the solution uses external air for cooling, which is more cost-effective and does not require additional processing or cooling media, nor does it require complex piping, pumps, or other liquid handling equipment. This simplicity brings higher reliability and facilitates maintenance.

[0031] In this embodiment, in order to reduce energy consumption, the outside air enters the first outside channel 402 and the second outside channel 502 in sequence. When in the first outside channel 402, the outside air exchanges heat with the air in the pre-cooling channel 401, absorbs the heat in the air in the pre-cooling channel 401, and reduces the air temperature in the pre-cooling channel 401, while the outside air temperature in the first outside channel 402 increases; then the outside air in the first outside channel 402 flows into the second outside channel 502 and exchanges heat with the air in the preheating channel 501. The air in the second outside channel 502 releases heat, and the air temperature in the preheating channel 501 increases.

[0032] Furthermore, the precooling channel 401 is separated from the first external channel 402 by the first substrate 403, the air inlet end of the precooling channel 401 is connected to the drying chamber 1, and the air outlet end of the precooling channel 401 is connected to the air duct of the evaporator 2; the preheating channel 501 is separated from the second external channel 502 by the second substrate 503, the air inlet end of the preheating channel 501 is connected to the evaporator 2, and the air outlet end of the preheating channel 501 is connected to the air duct of the condenser 3.

[0033] The high-temperature and high-humidity air (for example, temperature > 40°C) flowing out of the drying chamber 1 flows into the pre-cooling channel 401, and the external ambient air (for example, ambient temperature 25°C) flows into the first external channel 402. The pre-cooling channel 401 and the first external channel 402 are not connected to each other, and are separated by the first substrate 403, and heat is transferred through the first substrate 403; after the heat transfer, the temperature of the air entering the evaporator 2 in the pre-cooling channel 401 can be further reduced on the basis of the outlet of the drying chamber 1 (taking 30°C as an example), and then flows into the evaporator 2, and the temperature of the air flowing out of the first external channel 402 is correspondingly increased (taking 35°C as an example).

[0034] The low-temperature and low-humidity gas (for example, the temperature is 20°C) flowing out of the evaporator 2 flows into the preheating channel 501, and the air flowing out of the first external channel 402 flows into the second external channel 502 (taking 35°C as an example). The preheating channel 501 and the second external channel 502 are not connected to each other, and are separated by a second substrate 503, and heat is transferred through the second substrate 503; after heat transfer, the temperature of the air entering the condenser 3 in the preheating channel 501 can be increased based on the temperature of the gas flowing out of the evaporator 2 (taking 30°C as an example), and the temperature of the air flowing out of the second external channel 502 is correspondingly reduced, releasing the heat absorbed in the first external channel 402.

[0035] Furthermore, to enhance the heat exchange between precooling heat exchanger 4 and preheating heat exchanger 5, first substrate 403 and second substrate 503 are constructed from materials with high heat transfer efficiency. These can be metal substrates, such as extruded aluminum substrates or phase-change temperature-stabilizing plates. Other materials, as long as they enable heat transfer, are also acceptable. In this embodiment, the structure of preheating heat exchanger 5 is identical to that of precooling heat exchanger 4. In actual applications, a heat exchanger with a different structure from that of precooling heat exchanger 4 can be selected as preheating heat exchanger 5, as long as it can heat the air in the preheating channel.

[0036] Furthermore, in order to further improve the heat exchange effect of the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5, fins are provided on the substrate, and pre-cooling inner fins 404 and pre-cooling outer fins 405 are provided on the first substrate 403. The pre-cooling inner fins 404 are located in the pre-cooling channel 401, and the pre-cooling outer fins 405 are located in the first external channel 402. Figure 3 As shown, the figure shows the air flow direction in the pre-cooling channel 401 and the first external channel 402, Figure 3 Pre-cooling inner fins 404 are provided above the first substrate 403, and pre-cooling outer fins 405 are provided below the first substrate 403. The pre-cooling inner fins 404 divide the space above the first substrate 403 into several channels, which are the pre-cooling channels 401. After the wind in the circulating air duct flows out of the drying chamber 1, it enters the pre-cooling channel 401. The pre-cooling inner fins 404 increase the contact area between the pre-cooling heat exchanger 4 and the air, thereby improving the heat exchange effect of the pre-cooling heat exchanger; similarly, the pre-cooling outer fins 405 divide the space below the first substrate 403 into several channels, which are the first external channels 402. The external air enters the first external channels 402. The pre-cooling outer fins 405 increase the contact area between the pre-cooling heat exchanger 4 and the external air, thereby improving the heat exchange effect of the pre-cooling heat exchanger 4.

[0037] The air flow direction in the pre-cooling channel 401 can be opposite to the air flow direction in the first external channel 402. Through the convection of cold and hot air, heat can be transferred efficiently, thereby improving the heat exchange effect of the pre-cooling heat exchanger 4.

[0038] Furthermore, a preheating inner fin 504 and a preheating outer fin 505 are provided on the second substrate 503. The preheating inner fin 504 is located in the preheating channel 501, and the preheating outer fin 505 is located in the second external channel 502. Figure 3 As shown, the figure shows the air flow direction in the preheating channel 501 and the second external channel 502, Figure 3Preheating inner fins 504 are provided above the second substrate 503, and preheating outer fins 505 are provided below the second substrate 503. The preheating inner fins 504 divide the space above the second substrate 503 into several channels, which are the preheating channels 501. After the air in the circulating air duct flows out of the evaporation chamber 2, it enters the preheating channel 501. The preheating inner fins 504 increase the contact area between the preheating heat exchanger 5 and the air, thereby improving the heat exchange effect of the precooling heat exchanger; similarly, the preheating outer fins 505 divide the space below the second substrate 503 into several channels, which are the second external channels 502. The external air enters the second external channels 502. The preheating outer fins 505 increase the contact area between the preheating heat exchanger 5 and the external air, thereby improving the heat exchange effect of the preheating heat exchanger 5.

[0039] The air flow direction in the preheating channel 501 can be opposite to the air flow direction in the second external channel 502. Through the convection of cold and hot air, heat can be efficiently transferred, thereby improving the heat exchange effect of the preheating heat exchanger 5.

[0040] It should be pointed out that although Figure 3 The fins in the precooling heat exchanger 4 and the preheating heat exchanger 5 are of the same shape and number, but this is not a limitation of the present invention. Without departing from the basic principles of the present invention, those skilled in the art can flexibly adjust the shape and number of the fins in the precooling heat exchanger 4 and the fins in the preheating heat exchanger 5. As long as the air in the circulating air duct can be heat-exchanged to achieve the effect of initial cooling or initial heating, this does not deviate from the principles of the present invention and therefore falls within the scope of protection of the present invention. In addition, the shape and number of the precooling inner fins 404 and the precooling outer fins 405, as well as the shape and number of the preheating inner fins 504 and the preheating outer fins 505, can be the same or different.

[0041] Furthermore, the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5 can be independent units or connected together as two parts of a whole, as long as the connection sequence of the circulating air duct is maintained. When the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5 are integrated, it is convenient for the staff to install and also facilitates the configuration of the air duct structure. To make the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5 an integrated whole, the first base plate 403 and the second base plate 503 can be connected.

[0042] Figure 3 This is a simplified structural diagram. Figure 3The specific structure of the overall circulation air duct is not shown in the figure, but along the flow direction of the air, the pre-cooling channel 401 and the preheating channel 501 are arranged in the circulation air duct in sequence, that is, the air first flows into the pre-cooling channel 401 and then passes through the evaporator 2 before flowing into the preheating channel 501, and the air in the circulation air path does not pass through the pre-cooling channel 401 and the preheating channel 501 at the same time; similarly, along the flow direction of the air, the first external channel 402 and the second external channel 502 are connected to the outside world in sequence, that is, the outside air first flows into the first external channel 402 and then flows into the second external channel 502, and the outside air does not pass through the first external channel 402 and the second external channel 502 at the same time, so that the heat absorbed by the outside air in the first external channel 402 can be utilized.

[0043] like Figure 3 As shown, Figure 3 The positional relationship between the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5 is shown in FIG. Figure 3 The figure shows that the precooling heat exchanger 4 and the preheating heat exchanger 5 are arranged in parallel, but this is not a limitation of the present invention. Without departing from the basic principles of the present invention, those skilled in the art may arrange the precooling heat exchanger 4 and the preheating heat exchanger 5 in other ways, as long as the air in the circulating air duct can pass through the precooling channel 401 and the preheating channel 501 in sequence. For example, arranging the precooling heat exchanger 4 and the preheating heat exchanger 5 in parallel does not depart from the principles of the present invention and therefore falls within the scope of protection of the present invention.

[0044] Without departing from the basic principles of the present invention, those skilled in the art may employ a circulating air duct of any shape or structure, as long as the precooling channel 401 and the preheating channel 501 are sequentially located within the same air duct. When the precooling heat exchanger 4 and the preheating heat exchanger 5 are arranged side by side, a circulating air duct with a U-shaped air flow path may be employed. When the precooling heat exchanger 4 and the preheating heat exchanger 5 are arranged side by side, a circulating air duct with a linear air flow path may be employed. Similarly, the first external channel 402 and the second external channel 502 are located within the same air duct, and this duct may also employ any shape or structure, as long as the external air within the duct flows sequentially through the first external channel 402 and the second external channel 502.

[0045] Example 2

[0046] On the basis of the first embodiment, a third substrate 6 is added in this embodiment, such as Figure 2 and Figure 3As shown, since the first substrate 403 and the second substrate 503 have good heat transfer effects, in order to prevent heat transfer between the first substrate 403 and the second substrate 503, a third substrate 6 is provided between the first substrate 403 and the second substrate 503, and the first substrate 403 and the second substrate 503 are connected via the third substrate 6. The third substrate 6 is made of a material with poor heat transfer effects, so that the third substrate 6 can isolate the heat transfer between the first substrate 403 and the second substrate 503.

[0047] Furthermore, after the pre-cooling heat exchanger 4 and the pre-heating heat exchanger 5 become one, in order to simplify the arrangement of the air path structure, a fan 7 is provided on the second external channel 502. Figure 1 and Figure 2 As shown, a fan 7 is provided on the second external channel. After the fan 7 is started, the external air is sequentially transported to the first external channel 402 in the pre-cooling heat exchanger 4 and the second external channel 502 in the pre-heating heat exchanger 5. It should be noted that, although Figure 1 and Figure 2 A fan 7 is shown in the figure, but this is not a limitation of the present invention. Without departing from the basic principles of the present invention, those skilled in the art may use more than one fan, or set the fan at other positions, as long as the outside air can be transported to the first outside channel 402 and the second outside channel 405 in sequence, which does not deviate from the principles of the present invention and therefore falls within the scope of protection of the present invention.

[0048] A clothes drying method, using any of the above clothes dryers, such as Figure 4 As shown, the drying method includes: after the dryer is started, obtaining the temperature of the air flowing out of the drying chamber 1, and the air temperature can be obtained through a temperature sensor, etc.; comparing it with a first preset temperature value; and selecting to turn on the pre-cooling heat exchanger 4 or not according to the comparison result.

[0049] To save energy, this embodiment uses the temperature of the air flowing out of drying chamber 1 to determine whether to activate pre-cooling heat exchanger 4. When the temperature of the air flowing out of drying chamber 1 exceeds a first preset temperature value, pre-cooling heat exchanger 4 is activated for initial cooling. When the temperature of the air flowing out of drying chamber 1 is below the first preset temperature value, pre-cooling heat exchanger 4 is not activated. The first preset temperature value can be adjusted according to actual conditions, allowing the dryer to improve drying efficiency while appropriately reducing energy consumption.

[0050] The clothes drying method further includes: obtaining the temperature of the air flowing out of evaporator 2; comparing it with a second preset temperature value; and selecting whether to activate or deactivate preheating heat exchanger 5 based on the comparison result. To further reduce energy consumption, this method uses the temperature of the air flowing out of evaporator 2 to determine whether to activate preheating heat exchanger 5. When the temperature of the air flowing out of evaporator 2 is less than the second preset temperature value, preheating heat exchanger 5 is activated for initial temperature increase. When the temperature of the air flowing out of evaporator 2 is greater than the second preset temperature value, preheating heat exchanger 5 is deactivated. The second preset temperature value can be adjusted based on actual conditions, enabling the dryer to achieve improved drying performance while appropriately reducing energy consumption.

[0051] Those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims of this application, any of the claimed embodiments may be used in any combination.

[0052] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A clothes dryer, characterized in that: include: A drying chamber, wherein the drying chamber is used for placing items to be dried; an evaporator, the evaporator being arranged on an air outlet side of the drying chamber; a condenser, the condenser being arranged on an air outlet side of the evaporator; A pre-cooling heat exchanger, the pre-cooling heat exchanger comprising a pre-cooling channel and a first external channel that are not connected to each other, and the outside air enters the first external channel to initially cool the air in the pre-cooling channel; A preheating heat exchanger, the preheating heat exchanger comprising a preheating channel and a second external channel that are not connected to each other, and the outside air enters the second external channel to initially heat the air in the preheating channel; The drying chamber, the pre-cooling channel, the evaporator, the pre-heating channel, and the condenser sequentially constitute a circulating air duct; External air enters the first external channel and the second external channel in sequence.

2. The clothes dryer according to claim 1, characterized in that The pre-cooling channel and the first external channel are separated by a first substrate; The preheating channel and the second external channel are separated by a second substrate.

3. The clothes dryer according to claim 2, characterized in that Pre-cooling inner fins and pre-cooling outer fins are provided on the first substrate. The pre-cooling inner fins are located in the pre-cooling channel, and the pre-cooling outer fins are located in the first external channel.

4. The clothes dryer according to claim 2, wherein: Preheating inner fins and preheating outer fins are provided on the second substrate. The preheating inner fins are located in the preheating channel, and the preheating outer fins are located in the second external channel.

5. The clothes dryer according to claim 2, characterized in that The first substrate is connected to the second substrate.

6. The clothes dryer according to claim 5, characterized in that A third substrate is provided between the first substrate and the second substrate, and the third substrate is used to isolate heat transfer between the first substrate and the second substrate.

7. The clothes dryer according to claim 1, wherein: The second external channel is provided with a fan.

8. The clothes dryer according to claim 2, wherein: The first substrate and the second substrate are both metal substrates.

9. A method for drying clothes, characterized in that: The clothes drying method adopts the clothes drying machine according to any one of claims 1 to 8, and the clothes drying method comprises: Get the temperature of the air flowing out of the drying chamber; comparing with a first preset temperature value; The pre-cooling heat exchanger is selected to be turned on or off according to the comparison result.

10. The clothes drying method according to claim 9, characterized in that: The clothes drying method further comprises: Get the temperature of the air flowing out of the evaporator; comparing with a second preset temperature value; The preheating heat exchanger is selected to be turned on or off according to the comparison result.

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