Closed drying system and closed drying unit

Abstract

The utility model relates to a closed type drying system and a closed type drying unit, the closed type drying system comprises a refrigerant circulation loop which is formed by connecting a compressor, a condenser, a throttling element and a dehumidification evaporator through pipelines, and the compressor, the condenser, the throttling element and the dehumidification evaporator are connected through pipelines to form a loop; the heat pipe heat exchanger comprises an evaporation section and a condensation section which are communicated, the evaporation section is arranged on the air inlet side of the dehumidification evaporator, and the condensation section is arranged on the air inlet side of the condenser; the auxiliary heater is arranged on the air outlet side of the condenser; return air of the drying room sequentially passes through the evaporation section, the dehumidification evaporator and the condensation section, then is mixed with bypass return air and then is sent into the drying room through the condenser. The auxiliary heater is configured to act when the return air temperature is smaller than or equal to the first preset temperature, and stop acting when the return air temperature is larger than or equal to the second preset temperature. The utility model further provides a closed drying unit using the closed drying system.

Description

Technical Field

[0001] This utility model relates to the field of drying equipment technology, and in particular to a closed-loop drying system and closed-loop drying unit. Background Technology

[0002] Currently, closed-loop high-temperature dryers use total heat exchangers for heat recovery and total heat exchange. The total heat exchanger is rectangular, and the return air and the air after evaporation flow through it in an orthogonal manner. The warmer, more humid return air passes through the total heat exchanger to the dehumidifying evaporator, where it is cooled and dehumidified. The cooler, less humid evaporating air exits through the total heat exchanger in the opposite direction. The two types of air exchange heat within the total heat exchanger, achieving the purpose of total heat exchange.

[0003] However, using total heat exchangers for heat recovery has drawbacks such as high air resistance, low heat exchange efficiency, and complex structure. Furthermore, due to the structural characteristics of total heat exchangers, condenser fans and evaporator fans are also required. Meanwhile, traditional closed-loop dryers all utilize total heat exchangers for total heat recovery, meaning all return air from the drying chamber passes through the total heat exchanger for heat exchange before being heated by the condenser and finally entering the drying chamber. This total heat recovery method results in a lower condenser inlet air temperature, leading to a lower outlet air temperature after passing through the condenser, which cannot meet the higher drying temperature requirements of the drying chamber. Utility Model Content

[0004] The main technical problem solved by this utility model is to provide a control method, a closed drying system and a closed drying unit for a closed drying system with high heat exchange efficiency and which is conducive to increasing the air supply temperature.

[0005] To solve the above-mentioned technical problems, this utility model first provides a closed-loop drying system with the following technical solution:

[0006] A closed-loop drying system includes: a refrigerant circulation loop, comprising a compressor, a condenser, a throttling element, and a dehumidifying evaporator connected by pipes to form the loop;

[0007] A heat pipe heat exchanger includes an evaporation section and a condensation section connected together, wherein the evaporation section is located on the air inlet side of the dehumidifying evaporator, and the condensation section is located on the air inlet side of the condenser;

[0008] An auxiliary heater is provided on the air outlet side of the condenser;

[0009] The return air from the drying room passes through the evaporation section, the dehumidifying evaporator, and the condensation section in sequence, then mixes with the bypass return air, and is then sent into the drying room through the condenser.

[0010] The auxiliary heater is configured to activate when the return air temperature is less than or equal to a first predetermined temperature, and to deactivate when the return air temperature is greater than or equal to a second predetermined temperature.

[0011] Furthermore, a bypass airflow path is provided between the air inlet side of the condenser and the air inlet side of the evaporator to directly guide part of the return air from the drying room to the air inlet side of the condenser.

[0012] Furthermore, a damper is provided in the bypass airflow path, and the damper has a set opening degree to control the bypass airflow directly introduced into the air inlet side of the condenser to a set value.

[0013] Furthermore, the drying system also includes a fan on the air outlet side of the condenser, which drives the return air to complete the cooling, dehumidification, heating, and circulation processes.

[0014] Furthermore, the heat pipe heat exchanger is a flat plate heat pipe heat exchanger, which is inclinedly arranged between the condenser and the evaporator.

[0015] Another objective of this invention is to provide a closed-loop drying unit, which adopts the following technical solution:

[0016] A closed-loop drying unit includes a housing, within which a closed-loop drying system is installed. An evaporation chamber and a condensation chamber are separated within the housing by a partition. The condensation chamber is located above the evaporation chamber. A return air vent is provided on the housing of the evaporation chamber, and an air supply vent is provided on the housing of the condensation chamber. The evaporation section of a dehumidifying evaporator and a heat pipe heat exchanger is placed within the evaporation chamber, and the condensation section of a condenser and a heat pipe heat exchanger is placed within the condensation chamber. An auxiliary heater is located at the condenser.

[0017] Furthermore, the heat pipe heat exchanger is a flat plate heat pipe heat exchanger, and it is installed at an angle inside the shell. The angle of the heat pipe heat exchanger towards the dehumidifying evaporator is such that the angle between the heat pipe heat exchanger and the bottom plate of the shell is an acute angle.

[0018] Furthermore, the dehumidifying evaporator is vertically mounted on the bottom plate of the housing, and the top of the dehumidifying evaporator is connected to the heat pipe heat exchanger and / or the partition plate;

[0019] Alternatively, the dehumidifying evaporator is installed at an angle inside the housing, with the angle of the dehumidifying evaporator being the same as that of the heat pipe heat exchanger, and the top of the dehumidifying evaporator being connected to the partition plate.

[0020] Furthermore, the condenser is installed at an angle inside the housing, and the condenser is tilted in the same direction as the heat pipe heat exchanger. The top and bottom of the condenser are fixedly connected to the top plate and partition plate of the housing, respectively.

[0021] Alternatively, the condenser is vertically installed inside the housing, with its top and bottom fixedly connected to the top plate and partition plate of the housing, respectively.

[0022] Furthermore, a second air vent is provided on the partition plate located between the condenser and the condensing section of the heat pipe heat exchanger to form a bypass airflow path, and an air valve is installed at the second air vent.

[0023] In summary, the closed-loop drying system and closed-loop drying unit provided by this utility model have the following advantages compared with the prior art:

[0024] (1) This utility model sets up a heat pipe heat exchanger in the drying system, which replaces the commonly used total heat exchanger to realize the heat exchange between high temperature and high humidity air and low temperature and low humidity air. It has the characteristics of high efficiency and energy saving. It uses unique heat pipe technology to achieve efficient heat recovery and save energy costs. At the same time, the heat pipe heat exchanger also has the characteristics of low air flow resistance, low heat loss, high heat exchange efficiency, simple structure and small size. It can not only ensure heat exchange efficiency, but also help reduce the space occupied by the heat exchanger and reduce the volume of the unit.

[0025] (2) In this utility model, the return air of the drying room undergoes two dehumidification processes and two heat absorption processes, which solves the problem of high humidity and high heat recovery, improves the dehumidification effect of the drying system, and also increases the supply air temperature, greatly reducing the system energy consumption and meeting the requirements of humidity and temperature in the drying room.

[0026] (3) By setting a bypass airflow path between the return air inlet and the inlet side of the condenser, this utility model can control part of the return air not to exchange heat with the heat pipe heat exchanger during closed circulation. Instead, it can directly enter the condensing chamber through the bypass airflow path. The air after heat exchange in the condensing section of the heat pipe heat exchanger is mixed and then exchanged with the high-temperature refrigerant in the condenser. This is conducive to further increasing the temperature of the air after heat absorption and meeting the higher temperature requirements of the drying room for the drying air.

[0027] (4) This utility model can realize heat exchange in the wind field by installing only one fan in the unit, which simplifies the unit structure and reduces the unit cost.

[0028] (5) Set a preheating program before the drying and heating program. When the circuit is running for the first time, the preheating program is performed first to avoid the temperature inside the drying room dropping due to the operating temperature being lower than the operating temperature when the circuit is running for the first time.

[0029] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings. Attached Figure Description

[0030] The accompanying drawings, as part of this utility model, are used to provide a further understanding of the present utility model. The illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute an undue limitation of the present utility model. Obviously, the drawings described below are merely some embodiments; those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0031] In the attached diagram:

[0032] Figure 1 This is a schematic diagram of the unit structure of this utility model. Figure 1 ;

[0033] Figure 2 This is a schematic diagram of the unit structure of this utility model. Figure 2 ;

[0034] In the picture:

[0035] Shell 1, side plate 1a, bottom plate 1b, side plate 1c, top plate 1d, partition 2, evaporation chamber 3, condensation chamber 4, return air vent 5, supply air vent 6, dehumidifying evaporator 7, condenser 8, heat pipe heat exchanger 9, evaporation section 91, condensation section 92, first air vent 10, fan 11, bypass air passage 12, second air vent 13, electric heater 14.

[0036] It should be noted that the accompanying drawings and text description are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate this utility model, but are not intended to limit the scope of this utility model.

[0038] In the description of this utility model, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0039] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0040] This utility model first provides a closed-loop drying system, including a refrigerant circulation loop (not shown in the figure) and a heat pipe heat exchanger 9. Specifically, it includes the following two embodiments:

[0041] Example 1

[0042] like Figure 1 As shown, the refrigerant circulation loop includes a compressor (not shown in the figure), a condenser 8, a throttling element (not shown in the figure), and a dehumidifying evaporator 7, all connected by pipes to form the loop. The compressor compresses the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure superheated gas, which enters the condenser 8. In the condenser 8, the refrigerant releases heat and condenses into liquid refrigerant. The liquid refrigerant then passes through a throttling element such as an electronic expansion valve to reduce its pressure before entering the dehumidifying evaporator 7. In the dehumidifying evaporator 7, the refrigerant absorbs heat and evaporates into a low-pressure gas, which is then drawn back into the compressor, completing one cycle.

[0043] In this embodiment, the heat pipe heat exchanger 9 includes an evaporation section 91 and a condensation section 92. More preferably, the heat pipe heat exchanger 9 is a flat plate heat pipe heat exchanger, with the evaporation section 91 and the condensation section 92 arranged vertically, with the condensation section 92 located above the evaporation section 91. The heat pipe heat exchanger 9 is filled with a different refrigerant than that used in the refrigerant circulation path, as needed. The refrigerant in the heat pipe heat exchanger 9 absorbs heat and evaporates into a gaseous state in the lower evaporation section 91. Under the action of the pressure difference, the gaseous refrigerant moves to the condensation section 92, where it exchanges heat with the outside environment and releases heat to become a liquid refrigerant. The liquid refrigerant then flows back into the evaporation section 91 by gravity along the heat pipe, and the refrigerant circulates repeatedly within the heat pipe heat exchanger 9.

[0044] In this embodiment, the evaporation section 91 of the heat pipe heat exchanger 9 is placed on the air inlet side of the dehumidifying evaporator 7, and the condensation section 92 is placed on the air inlet side of the condenser 8. Thus, the high-humidity return air entering from the return air inlet 5 first absorbs heat through the evaporation section 91 of the heat pipe heat exchanger 9 before passing through the dehumidifying evaporator 7, which lowers the return air temperature and increases its relative humidity. Then, it releases heat a second time while passing through the dehumidifying evaporator 7, causing most of the moisture in the return air to condense and be discharged, achieving dehumidification. The lower-temperature return air with less moisture then continues to flow to the condensation section 92 of the heat pipe heat exchanger 9 for another heat absorption, increasing the return air temperature. Finally, it absorbs heat a second time through the condenser 8. The heated, high-temperature air is then delivered to the drying room through the air outlet 6 to dry the items inside.

[0045] In this embodiment, the return air of the drying room undergoes two dehumidification processes and two heat absorption processes to raise the temperature. This not only maximizes the dehumidification effect but also increases the supply air temperature, reduces system energy consumption, and meets the humidity and temperature requirements of the drying room.

[0046] In this embodiment, the closed drying system also includes a bypass airflow path 12, which can be used to directly lead part of the return air from the drying chamber to the air inlet side of the condenser 8, and more preferably directly to the condensing section 92 between the condenser 8 and the heat pipe heat exchanger 9.

[0047] In this way, during closed-loop circulation, a portion of the return air can be controlled to not exchange heat with the heat pipe heat exchanger 9, but instead flow directly into the air inlet side of the condenser 8 through the bypass airflow path 12. There, it mixes with the air that has undergone heat exchange in the condensing section 92 of the heat pipe heat exchanger 9, and then exchanges heat with the high-temperature refrigerant inside the condenser 8. Finally, it is delivered to the drying chamber through the air outlet 6. This allows the higher temperature of the return air to regulate the air inlet temperature of the condenser 8, thereby significantly increasing the temperature of the delivered air after heat absorption, meeting the higher temperature requirements of the drying chamber for the drying air.

[0048] In this embodiment, it is further preferred that a damper (not shown in the figure) is provided in the bypass airflow path. By controlling the opening degree of the damper, the inlet air temperature of the condenser 8 and the outlet air temperature after heat absorption can be adjusted, and it can even ensure that the outlet air temperature reaches above 120°C. In this embodiment, to simplify the control logic, it is further preferred that the damper is calibrated at the factory to set its opening degree, which is used to control the return air volume directly introduced into the inlet side of the condenser 8 to a set value. As long as there is return air, a fixed proportion of air volume enters the inlet side of the condenser 8 through the bypass airflow path 12.

[0049] In this embodiment, preferably, a fan 11 is installed on the return air path on the air inlet side of the evaporator section 91 of the heat pipe heat exchanger or on the air supply path on the exhaust side of the condenser 8 to meet the air circulation requirements. More preferably, the fan 11 is directly installed at the air supply outlet 6 or the return air outlet 5. Even more preferably, the fan 11 is installed at the air supply outlet 6 and is an axial flow fan. Under the action of the fan 11, the air in the drying chamber enters the shell 1 through the return air outlet 5, then passes sequentially through the evaporator section 91 of the heat pipe heat exchanger 9, the dehumidifying evaporator 7, the first air outlet 10, the condensing section 92 of the heat pipe heat exchanger 9, and the condenser 8, and finally is delivered to the drying chamber through the air supply outlet 6. The static pressure of the fan 11 is equal to the resistance of the evaporator section 91 of the heat pipe heat exchanger 9 + the resistance of the dehumidifying evaporator 7 + the resistance of the condensing section 92 of the heat pipe heat exchanger 9 + the resistance of the condenser 8. In this way, the air circulation within the unit can be driven by a single fan 11, which greatly simplifies the unit's structure and reduces costs.

[0050] Example 2

[0051] The refrigerant circulation loop is the same as in Example 1, except that, as Figure 2 As shown, an electric heater 14 is provided on the air outlet side of the condenser 8, and the electric heater 14 performs a preheating program.

[0052] The electric heater 14 is configured to heat the condenser and / or return air, so that the condenser 8 and return air temperatures reach the temperatures required for refrigerant evaporation.

[0053] Furthermore, the electric heater 14 is configured to operate when the return air temperature is less than or equal to a first predetermined temperature to heat the condenser and the return air, and to stop operating when the return air temperature is greater than or equal to a second predetermined temperature, which is considered as the temperature at the condenser 8 having reached the refrigerant evaporation temperature.

[0054] In the embodiments provided by this utility model, the refrigerant can be a commonly used one in the prior art, such as R134a. Preferably, in this application, R245fa refrigerant is used, that is, R245fa refrigerant is used in the refrigerant circulation loop. During the operation of the drying system, the air is heated by the auxiliary electric heater 14 to raise the return air temperature until it exceeds the evaporation temperature requirement of R245fa refrigerant. The refrigerant circulation system can achieve autonomous circulation, solving the low-pressure failure and compressor liquid slugging risk that are prone to occur in the closed drying system of the prior art, and realizing a single-stage R245fa closed ultra-high temperature drying heat pump system.

[0055] This utility model also provides a closed-loop drying unit, including a shell 1. The aforementioned closed-loop drying system is installed inside the shell 1. An evaporation chamber 3 and a condensation chamber 4 are separated within the shell 1 by a partition 2. The condensation chamber 4 is located above the evaporation chamber 3. A return air vent 5 is provided on the shell 1 of the evaporation chamber 3, and an air inlet 6 is provided on the shell 1 of the condensation chamber 4. The evaporation section 91 of the dehumidifying evaporator 7 and the heat pipe heat exchanger 9 is placed inside the evaporation chamber 3, and the condenser 8 and the condensation section 92 of the heat pipe heat exchanger 9 are placed inside the condensation chamber 4. Preferably, both the dehumidifying evaporator 7 and the condenser 8 are along the thickness direction of the shell 1 (i.e.,...). Figure 1 (The direction perpendicular to the paper) is set to the entire length.

[0056] In this embodiment, a water collection tray (not shown in the figure) is provided below the dehumidifying evaporator 7. After the dehumidifying evaporator 7 absorbs heat, the condensate on the surface of the dehumidifying evaporator 7 will be collected downwards in the water collection tray. The water collection tray is connected to the drain pipe, and the condensate is then discharged to the outside of the unit through the drain pipe.

[0057] In this embodiment, the heat pipe heat exchanger 9 is a flat plate heat pipe heat exchanger. The evaporation section 91 and the condensation section 92 are arranged vertically, with the condensation section 92 located above the evaporation section 91. Under the action of the pressure difference, the gaseous refrigerant moves upward to the upper condensation section 92. The gaseous refrigerant exchanges heat with the outside in the upper condensation section 92 and releases heat to become liquid refrigerant. The liquid refrigerant then flows down the heat pipe wall to the lower evaporation section 91 by gravity.

[0058] In this embodiment, the heat pipe heat exchanger 9 is arranged along the thickness direction of the shell 1, which helps to increase the heat exchange area and also helps to reduce the space occupied by the heat pipe heat exchanger 9 within the shell 1. The four sides of the flat plate heat exchanger are connected to the inner wall of the shell 1. Specifically, the bottom edge of the heat pipe heat exchanger 9 is connected to the bottom plate 1b of the shell 1, the top edge of the heat pipe heat exchanger 9 is connected to the other side plate 1c of the shell 1 opposite to the side plate 1a, and the top edge of the heat pipe heat exchanger 9 can also be connected to the top plate 1d of the shell 1. The front and rear sides of the heat pipe heat exchanger 9 are connected to the front and rear plates (not shown in the figure) of the shell 1. In this way, it can be ensured that all the air that needs to exchange heat with the heat pipe heat exchanger 9 can pass through the heat pipe heat exchanger 9 and will not flow through the gaps around it, thus affecting the heat exchange effect.

[0059] In this embodiment, it is further preferred that the return air inlet 5 and the supply air inlet 6 are located on the same side plate 1a of the housing 1, with the supply air inlet 6 located above the return air inlet 5. This helps to make the unit structure more compact, simplify the unit structure, and reduce the space occupied.

[0060] In this embodiment, preferably, the heat pipe heat exchanger 9 is installed at an angle inside the casing 1. This increases the airflow area of ​​the heat pipe heat exchanger 9 and improves its heat exchange efficiency. More preferably, in this embodiment, the angle α between the heat pipe heat exchanger 9 and the bottom plate of the casing 1 is 50-80°, with an optimal range of 60°-70°. This achieves the desired heat exchange effect while reducing airflow resistance and minimizing the space occupied by the heat pipe heat exchanger 9, thus reducing the overall size of the unit.

[0061] In this embodiment, it is further preferred that the tilting direction of the heat pipe heat exchanger 9 is such that the angle α between the heat pipe heat exchanger 9 and the bottom plate 1b of the shell 1 toward the evaporator 7 is an acute angle, that is, the heat pipe heat exchanger 9 tilts upward from the bottom end, from the direction close to the return air port 5 and the supply air port 6 toward the direction away from the return air port 5 and the supply air port 6.

[0062] In this embodiment, a first air vent 10 is provided on the partition 2. The first air vent 10 connects the evaporation chamber 3 and the condensation chamber 4. The first air vent 10 is located on the exhaust side of the dehumidifying evaporator 7, so that the air only flows upward into the condensation chamber 4 after passing through the dehumidifying evaporator 7 for heat exchange. An air flow path is formed between the return air vent 5, the evaporation section 91 of the heat pipe heat exchanger 9, the dehumidifying evaporator 7, the first air vent 10, the condensation section 92 of the heat pipe heat exchanger 9, the condenser 8, and the air supply vent 6.

[0063] In this embodiment, it is further preferred that the partition 2 is only disposed on the side of the heat pipe heat exchanger 9 facing the return air inlet 5 and the supply air inlet 6 (i.e. Figure 1 On the left side of the heat pipe heat exchanger 9, on the side of the heat pipe heat exchanger 9 away from the return air inlet 5 and the supply air inlet 6 (i.e. Figure 1 In this structure, the right side of the heat pipe heat exchanger 9 does not have a baffle 2. The top of the dehumidifying evaporator 7 is connected to the heat pipe heat exchanger 9, and it is connected at the junction of the evaporation section 91 and the condensation section 92. The dehumidifying evaporator 7 is completely open on the exhaust side, serving as the first air outlet 10. This simplifies the unit's structure and reduces the flow resistance generated by air flowing through the first air outlet 10.

[0064] In this embodiment, another implementation method is also provided, namely, on the side of the heat pipe heat exchanger 9 away from the return air inlet 5 and the supply air inlet 6 ( Figure 1 A partition 2 is also provided on the right side of the heat pipe heat exchanger 9, that is, the heat pipe heat exchanger 9 is installed through the partition 2. A first air vent 10 is opened on the partition 2 on the side of the heat pipe heat exchanger 9 away from the return air vent 5 and the supply air vent 6. In this structure, the top of the dehumidifying evaporator 7 can be connected to the heat pipe heat exchanger 9 or directly connected to the partition 2.

[0065] In this embodiment, it is further preferred that the dehumidifying evaporator 7 is vertically mounted on the bottom plate 1b of the casing 1, and the top of the dehumidifying evaporator 7 is connected to the heat pipe heat exchanger 9 (the junction between the evaporation section 91 and the condensation section 92). This ensures heat exchange efficiency, reduces airflow resistance, and also helps to reduce the space occupied by the heat pipe heat exchanger 9 and the dehumidifying evaporator 7, thereby reducing the overall size of the unit.

[0066] Regarding the installation structure of the dehumidifying evaporator 7, this embodiment also provides another implementation method. The dehumidifying evaporator 7 can also be installed in the housing 1 at an angle. The direction of inclination of the dehumidifying evaporator 7 is the same as the direction of inclination of the heat pipe heat exchanger 9, and the angle of inclination of the dehumidifying evaporator 7 is also the same as that of the heat pipe heat exchanger 9. That is, the dehumidifying evaporator 7 and the evaporation section 91 of the heat pipe heat exchanger 9 are arranged parallel to each other, and there is a certain distance between the dehumidifying evaporator 7 and the evaporation section 91 of the heat pipe heat exchanger 9. In this structure, a partition 2 needs to be provided above the dehumidifying evaporator 7, and the top and bottom of the dehumidifying evaporator 7 are connected to the partition 2 and the bottom plate 1b of the housing 1, respectively.

[0067] In this embodiment, it is further preferred that the condenser 8 is also installed at an angle inside the shell 1. The condenser 8 and the heat pipe heat exchanger 9 are in the same direction of inclination, and the inclination angle of the condenser 8 is also the same as that of the heat pipe heat exchanger 9. That is, the condenser 8 and the condensing section 92 of the heat pipe heat exchanger 9 are arranged in parallel, and there is a certain distance between the condenser 8 and the condensing section 92 of the heat pipe heat exchanger 9. In this structure, the top and bottom of the condenser 8 are connected to the top plate 1d and the partition plate 2 of the shell 1, respectively.

[0068] Regarding the installation structure of the condenser 8, this embodiment also provides another implementation method. The condenser 8 is installed vertically inside the housing 1. The condenser 8 is installed vertically between the top plate 1d and the partition plate 2 of the housing 1. In this structure, there is still a certain distance between the condenser 8 and the condensing section 92 of the heat pipe heat exchanger 9.

[0069] In this embodiment, a second air vent 12 is further preferably provided on the partition 2. The second air vent 12 is located on the air inlet side of the evaporation section 91 of the heat pipe heat exchanger 9 and on the partition 2 between the condensation section 92 of the heat pipe heat exchanger 9 and the condenser 8. An air valve is installed at the second air vent 12. The second air vent 12 forms a bypass airflow path between the return air vent 5 and the supply air vent 6. Part of the air entering from the return air vent 5 can directly enter the condensation chamber 4 through the second air vent 12 without exchanging heat with the heat pipe heat exchanger 9. Instead, it mixes with the air that has exchanged heat through the condensation section 92 of the heat pipe heat exchanger 9, and then exchanges heat with the high-temperature refrigerant in the condenser 8. This increases the air inlet temperature of the condenser 8, which is beneficial for significantly increasing the supply air temperature after heat absorption, meeting the higher temperature requirements of the drying room for drying air, and even ensuring that the supply air temperature reaches above 120°C.

[0070] In this embodiment, the airflow direction of the closed-loop dryer unit is as follows:

[0071] 1. Under the action of the fan 11, the high temperature and high humidity return air in the drying room enters the evaporation chamber 3 of the dryer unit shell 1 from the return air inlet 5;

[0072] 2. A small portion of the return air enters the air inlet side of the condenser 8 inside the condensing chamber 4 through the second air inlet 12;

[0073] 3. Most of the return air passes through the evaporation section 91 of the heat pipe heat exchanger 9. The refrigerant in the heat pipe heat exchanger 9 absorbs the heat in the return air and evaporates into a gaseous state, thus initially cooling the return air. The liquid refrigerant in the evaporation section 91 absorbs heat, becomes a gaseous refrigerant, and moves upward into the condensation section 92 above. At this time, the high temperature and high humidity return air releases heat and its temperature drops after passing through the evaporation section 91. The relative humidity of the return air increases. Driven by the fan 11, the return air continues to flow to the dehumidifying evaporator 7. After passing through the dehumidifying evaporator 7, the temperature of the return air drops further, and most of the moisture it contains condenses into water and flows out from the drain pipe, thus achieving the cooling and dehumidification of the return air.

[0074] 4. The return air, which is cooler and has less moisture after cooling and dehumidification, continues to flow upward through the first air outlet 10 into the condensing chamber 4. As described in Example 1, the condensing section 92 of the upper part of the heat pipe heat exchanger is inserted into the condensing chamber 4. The return air entering the condensing chamber flows to the condensing section 92 of the heat pipe heat exchanger 9. The refrigerant in the condensing section 92 condenses and releases heat, and the refrigerant condenses into a liquid state. The refrigerant liquid then flows down along the heat pipe back to the evaporation section 91 to continue absorbing heat and evaporating. The return air exchanges heat with the refrigerant in the heat pipe heat exchanger 9. The heat emitted when the refrigerant condenses is transferred to the return air, which initially heats the cooled return air. The initially heated return air mixes with the uncooled and undehumidified primary return air that enters directly from the second air outlet 12 and then reaches the condenser 8.

[0075] 5. The mixed air exchanges heat with the high-temperature refrigerant in the condenser 8. After being heated by the condenser 8, the temperature of the mixed air increases, and finally, under the action of the fan 11, it is sent out from the air outlet 6 into the drying room. Under the action of the fan 11, this cycle continues, which reduces the humidity and increases the temperature in the drying room, thereby achieving the purpose of drying the items.

[0076] This utility model further provides a control method for a closed-loop drying system. The closed-loop drying system and closed-loop drying unit provided in Embodiment 2 described above implement the control method provided in this embodiment. The drying unit is connected to the drying chamber and provides the heat required for drying to the drying chamber according to a set program. The return air inlet 5 on the casing 1 is connected to the return air channel of the drying chamber, and the air inlet 11 is connected to the air inlet channel of the drying chamber. The controller of the closed-loop drying system is equipped with a preheating program and a drying heating program. When the system is started, it first detects the temperature at a predetermined location and, based on the detected real-time temperature, determines whether to execute the preheating program first and then the drying heating program, or to directly execute the drying heating program. Specifically:

[0077] S1, when the machine is powered on, detects the temperature at a predetermined location.

[0078] As mentioned above, temperature sensors are installed at five return air inlets to monitor the return air temperature of the drying chamber in real time. After receiving the start-up command, the temperature sensors monitor the temperature at the return air inlets in real time.

[0079] In practical applications, the predetermined location includes, but is not limited to, the return air temperature; it can also be any location within the drying chamber that can fully reflect the temperature inside the drying chamber. The detected real-time temperature is then sent to the closed-loop drying system.

[0080] S2 determines the operating mode of the drying system based on the received real-time temperature.

[0081] The operating modes include a preheating program and a drying heating program. Specifically:

[0082] The trigger conditions for the preheating and drying heating programs are set, including but not limited to refrigerant temperature, refrigerant pressure, and the real-time temperature at a specific location in the drying chamber / return air vent as mentioned above. In this embodiment, the real-time temperature at the return air vent is used as the trigger condition to control the operation mode of the closed-loop drying system and the switching between modes.

[0083] After receiving the power-on signal, the temperature sensor at the return air vent collects real-time temperature data and sends it to the controller. The controller then determines and operates the corresponding mode based on the comparison between the real-time temperature data and the preset data.

[0084] When the real-time temperature at the predetermined location is detected to be less than or equal to the first predetermined temperature, a preheating procedure is executed separately.

[0085] When the return air temperature at the return air vent is less than or equal to the first predetermined temperature, the electric heater 14 is activated, while the refrigerant circulation loop does not operate, and the electric heater 14 is used to heat the drying chamber.

[0086] Preferably, when the electric heater 14 is working, the condenser fan operates, sending the heat generated by the electric heater 14 into the drying chamber through the air inlet, thereby increasing the temperature of the drying chamber.

[0087] Preferably, the initial temperature of the electric heater is low, which may be lower than the return air temperature of the drying chamber. If the electric heater 14 and the condenser fan operate simultaneously, cold air lower than the drying chamber temperature will be supplied to the drying chamber, causing temperature fluctuations. Therefore, after the electric heater has operated for a predetermined time, allowing its heat to accumulate to a temperature not lower than the return air temperature, the condenser fan will then operate. It should be noted that the predetermined operating time of the electric heater 14 is dynamic data; this predetermined time varies for drying systems with different power (heat output), and the controller determines the predetermined time required for this start-up operation based on the pre-input power of the electric heater 14 and the current return air temperature. After the predetermined time, the condenser fan operates, delivering the heat generated by the electric heater into the drying chamber.

[0088] When the real-time temperature at the predetermined location is greater than or equal to the second predetermined temperature, the preheating program is stopped and the drying heating program is executed. The refrigerant circulation loop is activated, and the refrigerant evaporates in the condenser, releasing heat. At this time, the condenser fan is turned on to send the heat generated by the condenser into the drying chamber, and the temperature of the drying chamber is increased by relying on the heat of the condenser.

[0089] When the electric heater 14 is heating the drying chamber, it can simultaneously raise the temperature at the condenser 8, increasing the condenser temperature and / or return air temperature to above the required evaporation temperature of R245fa refrigerant. This allows R245fa refrigerant to operate throughout the single-stage closed-loop dryer unit. Therefore, the second predetermined temperature is greater than or equal to the evaporation temperature of R245fa refrigerant.

[0090] Preferably, during the initial operation of the drying system, the condenser temperature is lower than the normal operating temperature, even lower than the current operating temperature of the electric heater 14 and / or the current temperature of the drying chamber. Therefore, if the electric heater 14 is directly stopped and the lower-temperature condenser is used to heat the drying chamber, it will cause temperature fluctuations in the drying chamber. Therefore, when the return air temperature is greater than or equal to the second predetermined temperature, the electric heater 14 does not stop working directly, but works simultaneously with the condenser 8 for a predetermined time, providing heat to the drying chamber at the same time. When the return air temperature is greater than or equal to the third predetermined temperature, the electric heater 14 is stopped, that is, the preheating program is stopped, and the system enters the condenser 8's independent cooling stage, that is, the drying heating program is executed independently.

[0091] Preferably, when the preheating and drying heating programs are running simultaneously, the temperature of the condenser 8 gradually rises as the refrigerant circulates continuously. Therefore, during this process, the output power of the electric heater 14 is controlled to gradually decrease the heat supply, resulting in an overall downward trend, ensuring that the heat from the electric heater 14 and the condenser 8 remains relatively balanced. Temperature rise curves / data of condensers with different rated evaporation capacities operating at different temperatures are pre-calculated, and the corresponding electric heater power control algorithm is pre-stored in the controller. Based on the pre-acquired condenser temperature rise curves / data, the algorithm obtains the real-time power of the electric heater 14 at each time point, thus maintaining the total heat from the electric heater 14 and the condenser 8 in a relatively balanced state, i.e., the total heat remains constant or fluctuates slightly within an allowable range. When the condenser 8 reaches its optimal evaporation state, and the heat is maintained at a relatively stable, high temperature, the heat from the electric heater 14 is at its minimum, thus stopping the electric heater 14 and entering a separate condenser heating process, i.e., executing the drying heating program independently.

[0092] Alternatively, a third predetermined temperature can be set, and when the return air temperature is greater than or equal to the third predetermined temperature, the electric heater 14 can be turned off. The first predetermined temperature ≤ the second predetermined temperature ≤ the third predetermined temperature ≤ the drying chamber setting temperature. When the third predetermined temperature is reached, the return air temperature is the same as or only slightly different from the drying chamber temperature, and turning off the electric heater 14 will not have a significant impact on the drying chamber temperature.

[0093] Preferably, when the return air temperature is greater than or equal to the second predetermined temperature, the preheating program + drying heating program is entered. During this process, the electric heater maintains a stable heat output to quickly increase the temperature of the drying chamber, so that the return air temperature quickly reaches the third predetermined temperature, and then the electric heater 14 is turned off.

[0094] In practical applications, based on the accuracy requirements of the drying temperature, the system can be set to either directly enter the drying heating program or use a preheating program + drying heating program when the return air temperature reaches the second set temperature. In the preheating program + drying heating program, the total heat sent into the drying chamber is controlled by using a stable output of the electric heater or by gradually reducing the heat of the electric heater.

[0095] During the drying and heating process, the required heat varies depending on the condition of the drying chamber, resulting in temperature fluctuations within the chamber. To maintain a constant temperature within the drying chamber, the evaporation rate of condenser 8 can be adjusted according to the drying requirements.

[0096] As mentioned above, in this embodiment, when the machine is turned on, the return air temperature is detected first. When the return air temperature is less than or equal to the first set temperature, the preheating program is executed. As the return air temperature (temperature in the drying chamber) continues to rise, when the return air temperature rises to the second predetermined temperature, the preheating program + drying heating program or the drying heating program is executed directly. When the preheating program + drying heating program is executed, the drying heating program is executed when the return air temperature reaches the third predetermined temperature.

[0097] The first, second, and third predetermined temperatures can be set according to the evaporation temperature of the refrigerant. In this embodiment, R245fa refrigerant flows through the refrigerant circulation pipeline. Therefore, based on the characteristics of this refrigerant, the first predetermined temperature can be set to a value within the range of 42 to 48°C, such as 45°C; the second predetermined temperature can be set to a value within the range of 48 to 55°C, such as 50°C; and the third predetermined temperature can be set to a value within the range of 52 to 60°C, such as 55°C. This means the evaporation temperature of the R245fa refrigerant is presumably around 50°C. When the return air temperature reaches the second predetermined temperature, i.e., the temperature at the condenser has reached the evaporation temperature of the refrigerant, R245fa evaporation circulation heating can be directly initiated. The specific values ​​of the three predetermined temperatures can be determined based on the set temperature of the drying chamber, ensuring that the first predetermined temperature ≤ the second predetermined temperature ≤ the third predetermined temperature ≤ the set temperature for drying in the drying chamber; no specific requirements or restrictions apply.

[0098] During initial operation, when the first predetermined temperature < return air temperature < second predetermined temperature, the temperature inside the drying chamber is relatively high, allowing direct entry into the preheating + drying heating program. Simultaneously, the condenser fan activates, delivering heat from the condenser and heater into the drying chamber. Further, when the first predetermined temperature < return air temperature < second predetermined temperature, the electric heater operates for a predetermined time before the condenser fan and condenser activate simultaneously, delivering heat from both into the drying chamber. Before the condenser fan activates, the electric heater operates, increasing its heating temperature and simultaneously heating the condenser, thus raising its temperature to near the evaporation temperature of R245fa, achieving normal evaporative heat release cycle of the refrigerant.

[0099] When the initial operation begins, if the second predetermined temperature is less than the return air temperature, the temperature at the condenser has already reached the refrigerant evaporation temperature, and the drying and heating program can be executed directly.

[0100] The above solution has the following beneficial effects:

[0101] 1. This drying system uses a heat pipe heat exchanger 9, which replaces the commonly used total heat exchanger to achieve heat exchange between high-temperature and high-humidity air and low-temperature and low-humidity air. It has the characteristics of high efficiency and energy saving. It uses unique heat pipe technology to achieve efficient heat recovery and save energy costs. At the same time, the heat pipe heat exchanger also has the characteristics of low air flow resistance, low heat loss, high heat exchange efficiency, simple structure and small size. It can not only ensure heat exchange efficiency, but also help to reduce the space occupied by the heat exchanger and reduce the size of the unit.

[0102] 2. This drying system dehumidifies the return air from the drying room twice, and also heats it twice. This solves the problem of high humidity and high heat recovery, improves the dehumidification effect of the drying system, and increases the supply air temperature, which greatly reduces the system's energy consumption and meets the humidity and temperature requirements of the drying room.

[0103] 3. This drying system only requires one fan 11 to achieve airflow heat exchange, which simplifies the unit structure and reduces the unit cost.

[0104] 4. The drying system has a second air vent 12 on the partition 2 between the condenser 8 and the condensing section 92 of the heat pipe heat exchanger 9. The second air vent 12 forms a bypass airflow path between the return air vent 5 and the supply air vent 6. Part of the air entering from the return air vent 5 can directly enter the condensing chamber 4 through the second air vent 12 without exchanging heat with the heat pipe heat exchanger 9. Instead, it mixes with the air that has exchanged heat with the condensing section 92 of the heat pipe heat exchanger 9, and then exchanges heat with the high-temperature refrigerant in the condenser 8. This increases the inlet air temperature of the condenser 8, which is beneficial for significantly increasing the supply air temperature after heat absorption. This meets the higher temperature requirements of the drying room for drying air and can even ensure that the supply air temperature reaches above 120℃.

[0105] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present utility model. The implementation schemes in the above embodiments can be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A closed-loop drying system, characterized in that: include, The refrigerant circulation loop consists of a compressor, condenser, throttling element, and dehumidifying evaporator connected by pipes to form the loop; A heat pipe heat exchanger includes an evaporation section and a condensation section connected together, wherein the evaporation section is located on the air inlet side of the dehumidifying evaporator, and the condensation section is located on the air inlet side of the condenser; An auxiliary heater is provided on the air outlet side of the condenser; The return air from the drying room passes through the evaporation section, the dehumidifying evaporator, and the condensation section in sequence, then mixes with the bypass return air, and is then sent into the drying room through the condenser. The auxiliary heater is configured to activate when the return air temperature is less than or equal to a first predetermined temperature, and to deactivate when the return air temperature is greater than or equal to a second predetermined temperature.

2. The closed-loop drying system according to claim 1, characterized in that: A bypass airflow path is also provided between the air inlet side of the condenser and the air inlet side of the evaporator to directly guide part of the return air from the drying room to the air inlet side of the condenser.

3. The closed-loop drying system according to claim 2, characterized in that: A damper is provided in the bypass airflow path. The damper has a set opening degree to control the bypass airflow directly introduced into the air inlet side of the condenser to a set value.

4. The closed-loop drying system according to claim 1, characterized in that: The drying system also includes a fan on the air outlet side of the condenser, which drives the return air to complete the cooling, dehumidification, and heating cycle.

5. The closed-loop drying system according to any one of claims 1 to 4, characterized in that: The heat pipe heat exchanger is a flat plate heat pipe heat exchanger, which is inclinedly arranged between the condenser and the evaporator.

6. A closed-loop drying unit, characterized in that: The device includes a housing, within which a closed-loop drying system as described in any one of claims 1 to 5 is installed. An evaporation chamber and a condensation chamber are separated within the housing by a partition. The condensation chamber is located above the evaporation chamber. A return air vent is provided on the housing of the evaporation chamber, and an air supply vent is provided on the housing of the condensation chamber. The evaporation section of the dehumidifying evaporator and the heat pipe heat exchanger is placed in the evaporation chamber, and the condensation section of the condenser and the heat pipe heat exchanger is placed in the condensation chamber. An auxiliary heater is provided at the condenser.

7. The closed-loop drying unit according to claim 6, characterized in that: The heat pipe heat exchanger is a flat plate heat pipe heat exchanger, and it is installed at an angle inside the shell. The angle of the heat pipe heat exchanger towards the dehumidifying evaporator is an acute angle between the heat pipe heat exchanger and the bottom plate of the shell.

8. The closed-loop drying unit according to claim 7, characterized in that: The dehumidifying evaporator is vertically mounted on the bottom plate of the housing, and the top of the dehumidifying evaporator is connected to the heat pipe heat exchanger and / or the partition plate; Alternatively, the dehumidifying evaporator is installed at an angle inside the housing, with the angle of the dehumidifying evaporator being the same as that of the heat pipe heat exchanger, and the top of the dehumidifying evaporator being connected to the partition plate.

9. The closed-loop drying unit according to claim 7, characterized in that: The condenser is installed at an angle inside the housing, and the condenser is tilted in the same direction as the heat pipe heat exchanger. The top and bottom of the condenser are fixedly connected to the top plate and partition plate of the housing, respectively. Alternatively, the condenser is vertically installed inside the housing, with its top and bottom fixedly connected to the top plate and partition plate of the housing, respectively.

10. The closed-loop drying unit according to any one of claims 6 to 9, characterized in that: A second air vent is provided on the partition plate located between the condenser and the condensing section of the heat pipe heat exchanger to form a bypass airflow path, and an air valve is installed at the second air vent.

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