A direct expansion type radiant cooling terminal, anti-condensation method and cooling system

Abstract

The application discloses a direct expansion type radiation cooling terminal, a dew prevention method and a cooling system, and mainly relates to the technical field of building air conditioners and radiation cooling. The application discloses a direct expansion type radiation cooling terminal, a dew prevention method and a cooling system, and mainly relates to the technical field of building air conditioners and radiation cooling. The application discloses a direct expansion type radiation cooling terminal, a dew prevention method and a cooling system, and mainly relates to the technical field of building air conditioners and radiation cooling. The application discloses a direct expansion type radiation cooling terminal, a dew prevention method and a cooling system, and mainly relates to the technical field of building air conditioners and radiation cooling. The application discloses a direct expansion type radiation cooling terminal, a dew prevention method and a cooling system, and mainly relates to the technical field of building air conditioners and radiation cooling.

Description

Technical Field

[0001] This invention relates to the field of building air conditioning and radiant cooling technology, specifically a direct expansion radiant cooling terminal, an anti-condensation method, and a cooling system. Background Technology

[0002] Radiant cooling technology, as a low-energy cooling method, is considered a highly promising low-energy cooling solution due to its superior thermal comfort, low operating energy consumption, and good quiet operation. In particular, the direct expansion radiant cooling system, in which the refrigerant directly evaporates and absorbs heat in the capillary network or heat exchange coils at the radiant terminals, eliminates the intermediate water circulation link, reduces secondary heat exchange losses, and, due to its smaller capacity and faster response speed, exhibits significant energy-saving potential.

[0003] However, during the actual operation of the system, due to the low local evaporation temperature, when the indoor humidity is high and the substrate surface temperature is close to the dew point, condensation is easily formed, resulting in the formation of water droplets or water films. This not only affects indoor comfort but may also cause damage to the terminal or decoration materials.

[0004] To address the above problems, there are three existing solutions: The first approach is to improve the hardware structure or material type. For example, the invention patent with publication number CN115560400A discloses a temperature control device for preventing condensation in nuclear power plant air conditioning units. It integrates a canopy-shaped heating wire inside the air outlet for active temperature compensation and sets up an adjustment cylinder composed of highly absorbent material and activated carbon fiber particles. It reduces air humidity and temperature difference through the dual effects of heating and adsorption. However, the operation of the heating wire increases additional energy consumption, and the absorbent material also needs to be maintained and replaced regularly. In essence, it is a passive response remedy, which is weak in preventing sudden changes in humidity. The utility model patent with publication number CN217464848U adds a desiccant interlayer and a porous structure between the radiant panel and the indoor environment. Humidity regulating panels utilize a low-humidity environment created by a desiccant to drive the panel to continuously absorb moisture and regenerate, thereby passively regulating the humidity near the wall surface. However, this method relies on the physical properties of the materials, has a slow dynamic response, cannot cope with instantaneous moisture loads, and the desiccant has a defined moisture absorption saturation cycle, requiring regular manual replacement, which is inconvenient. The utility model patent with publication number CN220958628U proposes an idea of ​​embedding an infrared material heat-equalizing layer and combining it with precise temperature control. It controls the panel surface temperature by adjusting the water circuit to prevent condensation and activates electric heating to directly supplement heat when the heating supply is insufficient. However, it introduces high-cost precious metal materials and a complex control system, and the energy utilization quality of the electric heating supplementary heating method is low, which may affect the overall system energy efficiency.

[0005] The second approach is to construct a control strategy or optimization algorithm. The core idea is to dynamically optimize operating parameters (water temperature, air temperature, flow rate, etc.) by building a system model and applying advanced control algorithms (such as model predictive control (MPC) and machine learning). This predicts and avoids condensation risks from the system control logic level, while also taking energy efficiency into account. For example, the invention patent with publication number CN119983519A proposes a dynamic optimization algorithm based on model predictive control (MPC), which takes radiation as the main strategy and fresh air as the main strategy, continuously optimizes water temperature and air temperature, and triggers protection at the condensation risk threshold. However, the implementation of this method is highly dependent on an accurate and calibrated system model, and has high requirements for sensor accuracy and controller computing power, resulting in high engineering threshold and initial cost.

[0006] The third approach is to integrate a comprehensive system with intelligent control. The core idea is to build a complex system that integrates environmental perception, digital modeling, simulation prediction, multi-objective optimization, and intelligent decision-making. It usually combines the technical elements of the first two types and aims to achieve integrated, adaptive, and globally optimal anti-condensation and efficient operation. For example, the invention patent with publication number CN120819882A constructs a multi-module intelligent system that integrates environmental perception, load simulation, dynamic control, and anti-condensation protection. It achieves dynamic limiting of water supply temperature based on dew point temperature difference through closed-loop control. The significant problem with this system is the difficulty of integration and debugging due to its high complexity, the high overall cost, and the potential reliability risks under multi-module coupling. It may only be suitable for specific large-scale high-end projects.

[0007] In summary, the main problems with existing technologies are that raising the surface temperature of the radiant panel to prevent condensation reduces the radiant cooling capacity and affects the system's energy efficiency; using electric auxiliary heating or adding an independent dehumidification system will consume additional energy; existing anti-condensation coatings or moisture-absorbing materials can only passively absorb or buffer moisture, lacking effective automatic regeneration methods; and relying on complex sensor networks and algorithm models makes the system complex, costly, and poorly adaptable. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and provide a direct expansion radiant cooling terminal, an anti-condensation method and a cooling system. By setting a humidity buffer layer on the surface of the radiant plate, the condensate is absorbed and temporarily stored, delaying the formation of visible condensation. Combined with the heating mode of the direct expansion refrigeration system, the humidity buffer layer is actively regenerated, while promoting the return of lubricating oil, thereby improving system stability and radiant cooling efficiency.

[0009] To achieve the above objectives, the present invention employs the following technical solution: A direct expansion radiant cooling terminal includes: substrate; A thermally conductive layer is disposed on the side of the substrate facing the interior. A humidity buffer layer is disposed on the side of the thermally conductive layer away from the substrate; The flow channel is located on the side of the heat-conducting layer away from the humidity buffer layer, and the refrigerant directly evaporates and exchanges heat within the flow channel; A sensor, installed within the humidity buffer layer, is used to monitor the temperature or capacitance of the humidity buffer layer and send the monitoring results to the controller. The humidity buffer layer is made of a material that can absorb, temporarily store, and diffuse condensate. During radiant cooling operation, the humidity buffer layer absorbs, temporarily stores, and diffuses surface condensate to delay the formation of visible condensation. Furthermore, in heating operation mode, the heat released by the condensation of the refrigerant can evaporate and remove the moisture in the humidity buffer layer.

[0010] Preferably, the substrate has a mounting groove adapted to the flow channel on the side facing the interior. A heat-equalizing layer is provided on the surface of the substrate facing the interior and the inner wall of the mounting groove. The heat-equalizing layer is used to uniformly distribute the cold energy generated by the flow channel laterally.

[0011] Preferably, the humidity buffer layer is made of a material with hydrophilicity and water storage capacity, which temporarily stores surface condensate through capillary absorption, physical adsorption, or chemical bonding.

[0012] Preferably, the humidity buffer layer comprises an inorganic material capable of undergoing a reversible hydration-dehydration reaction with water.

[0013] Preferably, the inorganic material is a hydrated salt material.

[0014] Preferably, the humidity buffer layer further comprises an adhesive or a porous carrier.

[0015] Preferably, the flow channel is a capillary structure or a microchannel structure.

[0016] Preferably, the thermal resistance of the heat-conducting layer should ensure that, under normal radiant cooling conditions, the surface temperature of the humidity buffer layer and the direct expansion radiant cooling terminal is not lower than the dew point temperature; and under heating conditions, the heat-conducting layer transfers condensation heat to promote the regeneration of the humidity buffer layer.

[0017] A method for preventing condensation using a direct expansion radiant cooling terminal involves absorbing, temporarily storing, and diffusing condensate on the surface of the direct expansion radiant cooling terminal through a humidity buffer layer during radiant cooling operation. When the sensor detects that the humidity buffer capacity of the humidity buffer layer is close to the threshold, the direct expansion radiant cooling system switches to heating operation mode to regenerate the humidity buffer layer in situ.

[0018] A direct expansion radiant cooling system includes the aforementioned direct expansion radiant cooling terminal.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention can buffer and delay condensation on the surface of a direct expansion radiant cooling terminal. By setting a humidity buffer layer, when the surface temperature approaches or reaches the condensation condition, this layer can absorb, temporarily store, and diffuse condensate, delaying the formation of visible condensation and reducing the risk of water droplets or water films appearing on the surface. This mechanism can effectively cope with short-term condensation problems caused by sudden changes in environmental humidity or operating conditions, thereby improving the operational stability of the terminal.

[0020] 2. When the direct expansion radiant cooling system switches to heating mode, this invention utilizes the heat released by refrigerant condensation to evaporate and remove moisture from the humidity buffer layer, achieving active regeneration of this layer. This process does not require additional dedicated regeneration equipment; instead, it utilizes the inherent low-grade waste heat during system operation (such as the heat from the oil return stage) to integrate functional maintenance with system operation.

[0021] 3. This invention also takes into account the system's oil return function, enabling long-term operation. In heating mode, the flow of refrigerant and the condensation heat exchange process simultaneously promote the return of lubricating oil to the compressor along with the refrigerant, which helps maintain the lubrication and long-term reliable operation of the direct expansion radiant cooling system, achieving the dual benefits of anti-condensation regeneration and system maintenance.

[0022] 4. This invention improves radiative cooling efficiency. The humidity buffer layer delays surface condensation, eliminating the need for the system to raise the radiative surface temperature to prevent condensation. This maintains a lower surface operating temperature, ensuring high radiative cooling capacity and system energy efficiency. This invention does not rely on additional electrical energy for active heating, nor does it significantly increase the terminal temperature, avoiding the potential decrease in cooling efficiency or increased energy consumption associated with traditional anti-condensation methods.

[0023] 5. Based on the material properties, this invention improves system reliability by autonomously responding. The humidity buffer layer is made of a composite material with moisture absorption and heat release / moisture release and heat absorption properties, which can autonomously and in real time adjust according to changes in local thermal and humidity environment. From a physical mechanism perspective, it avoids the dependence on preset parameters such as fixed humidity and temperature difference, and also reduces the need for precision sensors and complex electronic control systems, thereby improving the hardware fault tolerance and operational reliability of the system.

[0024] 6. The present invention has a simple structure, is easy to integrate and promote. It can achieve its function by simply introducing a humidity buffer layer on the surface of the existing direct expansion radiant cooling terminal. The structure is flexible and easy to integrate with the existing terminal, making it suitable for promotion and application in building cooling systems. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention.

[0026] The following figures are labeled: 1. Substrate; 2. Flow channel; 3. Humidity buffer layer; 4. Heat dissipation layer; 5. Thermal conductive layer. Detailed Implementation

[0027] The present invention will now be described in detail and completely with reference to the accompanying drawings and specific embodiments.

[0028] It should be noted that in the description of this invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. These terms are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. The terms "horizontal," "vertical," and "suspended," etc., do not indicate that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Example 1: As shown in the attached document Figure 1 As shown, the present invention describes a direct expansion radiant cooling terminal, comprising: Substrate 1, preferably with a heat-insulating structure, to prevent heat transfer with the back of the direct expansion radiative cooling terminal; A thermally conductive layer 5 is disposed on the side of the substrate 1 facing the interior. A humidity buffer layer 3 is disposed on the side of the thermally conductive layer 5 away from the substrate 1; The flow channel 2 is located on the side of the heat-conducting layer 5 away from the humidity buffer layer 3, and the refrigerant directly evaporates and exchanges heat in the flow channel 2; A sensor is installed inside the humidity buffer layer 3 to monitor the temperature or capacitance of the humidity buffer layer 3 and send the monitoring results to the controller. The humidity buffer layer 3 is made of a material capable of absorbing, temporarily storing, and diffusing condensate. During radiant cooling operation, the humidity buffer layer 3 absorbs, temporarily stores, and diffuses surface condensate to delay the formation of visible condensation. Furthermore, in heating operation mode, the heat released by the condensation of the refrigerant can evaporate and remove the moisture in the humidity buffer layer 3. Through the combination of passive buffering and active regeneration, the system achieves delayed condensation on the terminal surface, improved system stability, and optimized radiant cooling efficiency.

[0031] The humidity buffer layer 3 can be made of hydrophilic materials, hydrated salts or porous carriers, etc. The humidity buffer layer 3 does not replace the air-side dehumidification device, but is used to passively buffer the risk of surface condensation during radiant cooling.

[0032] Preferably, the substrate 1 has a mounting groove adapted to the flow channel 2 on the side facing the interior. A heat-spreading layer 4 is provided on both the surface of the substrate 1 facing the interior and the inner wall of the mounting groove. The heat-spreading layer 4 is used to uniformly distribute the cooling energy generated by the flow channel 2 laterally. The heat-spreading layer 4 can be made of a metallic thermally conductive material, such as copper or aluminum.

[0033] In this embodiment, the flow channel 2 can adopt a capillary structure, and the refrigerant evaporates directly in the capillary to achieve radiative cooling. To improve heat exchange uniformity, a heat equalization layer 4 is also provided to ensure that the cooling capacity of the refrigerant evaporation is evenly distributed on the surface of the substrate 1.

[0034] In this embodiment, the humidity buffer layer 3 is disposed on the outermost surface of the direct expansion radiant cooling terminal in the form of a coating, a cover or a composite layer, and forms continuous contact with the substrate 1 through the heat-conducting layer 5 and the heat-spreading layer 4, so as to facilitate the rapid absorption and spread of surface condensate.

[0035] In this embodiment, the thermally conductive layer 5 is used to establish a controlled heat transfer channel between the substrate 1 and the humidity buffer layer 3, so that the humidity buffering process and the radiative cooling process are thermally coupled. On the one hand, the thermally conductive layer 5 can transfer the heat released by refrigerant condensation in the heating operation mode to the humidity buffer layer 3 to promote the evaporation and removal of moisture in the humidity buffer layer 3; on the other hand, in the cooling operation, the thermally conductive layer 5 buffers the low temperature of the substrate 1 through its thermal resistance characteristics, thereby adjusting the working temperature of the humidity buffer layer 3 and its end surface to be higher than the refrigerant evaporation temperature, and avoiding direct surface condensation under normal operating conditions.

[0036] In this embodiment, the material type, thickness, and thermal conductivity of the heat-conducting layer 5 can be selected according to the refrigerant evaporation temperature and the designed cooling load. By adjusting its thermal resistance, precise control of the surface temperature of the radiant cooling terminal can be achieved. Under normal radiant cooling conditions, the heat-conducting layer 5 keeps the humidity buffer layer 3 and the terminal surface temperature above or close to the dew point temperature, thereby reducing or avoiding direct condensation. When the humidity buffer capacity reaches the threshold and the system switches to heating mode, the heat-conducting layer 5 can effectively transfer the condensation heat, completing the regeneration of the humidity buffer layer 3.

[0037] In this embodiment, the humidity buffer layer 3 is disposed on the outside of the heat-conducting layer 5, which can absorb, temporarily store, and diffuse the condensate formed on the surface of the radiant cooling terminal. When the surface temperature approaches or reaches the condensation condition during radiant cooling operation, the humidity buffer layer 3 plays a passive buffering role on the condensate, delaying the formation of visible condensation.

[0038] In this embodiment, the controller can be directly adopted from the controller of a direct expansion radiant cooling system. The controller can predict the state of the humidity buffer layer 3 based on sensor detection results and dehumidify it in advance during non-cooling operation. If a problem occurs during normal cooling, the compressor needs to operate at a reduced frequency. For example, when the sensor detects that the moisture in the humidity buffer layer 3 is close to the preset humidity buffer capacity threshold, the system can switch to heating operation mode during non-cooling operation. The refrigerant condenses and releases heat inside the substrate 1, and the released heat is transferred to the humidity buffer layer 3 via the heat-conducting layer 5, causing the temporarily stored moisture to evaporate and be removed, thereby achieving in-situ regeneration of the humidity buffer layer 3. Simultaneously, in heating operation mode, the refrigerant flow direction and condensation heat exchange process facilitate the return of lubricating oil to the compressor along with the refrigerant, improving system operational reliability.

[0039] In this embodiment, the humidity buffer layer 3 is made of a material with hydrophilicity and water storage capacity, which can temporarily store surface condensate through capillary absorption, physical adsorption or chemical bonding.

[0040] In this embodiment, the humidity buffer layer contains an inorganic material capable of undergoing a reversible hydration-dehydration reaction with moisture to increase the moisture buffering capacity per unit area.

[0041] The inorganic material is a hydrated salt material, which is selected from one or more of carbonate hydrates, sulfate hydrates, and chloride hydrates.

[0042] In this embodiment, the humidity buffer layer 3 further includes an adhesive or a porous carrier to fix the humidity buffer material and enhance its structural stability during multiple water absorption and regeneration processes.

[0043] The porous carrier can be made of porous ceramic, porous metal or porous inorganic substrate, and is used to form a connected liquid water transport channel to promote the diffusion and uniform distribution of condensate in the humidity buffer layer.

[0044] This embodiment improves system stability and radiative cooling efficiency through the synergistic mechanism of temperature regulation of the heat-conducting layer, delayed condensation of the humidity buffer layer, and direct expansion heating regeneration.

[0045] Example 2: The difference from Example 1 is that in this example, the flow channel 2 adopts a microchannel structure. Specifically, multiple microchannels are integrated inside the substrate 1, and the refrigerant directly evaporates and exchanges heat within the microchannels. The microchannel structure can improve heat exchange efficiency and reduce system volume. When the flow channel 2 adopts a microchannel structure, the heat spreader layer 4 may not be provided, or a thermally enhanced structure may be locally provided on the outside of the microchannel as needed.

[0046] The structure and function of the heat-conducting layer 5 and the humidity buffer layer 3 are the same as in Example 1. The heat-conducting layer 5 controls the thermal resistance of the refrigerant evaporation temperature, ensuring the radiative cooling capacity while keeping the terminal surface temperature in a range that is conducive to delaying condensation. When the humidity buffer capacity reaches the threshold, the humidity buffer layer 3 is regenerated through the heating mode.

[0047] Example 3: Based on Example 1, this example provides a humidity buffer layer 3, which can be prepared using a composite material and mainly includes: Hydrated salt materials capable of undergoing reversible hydration-dehydration reactions with water account for approximately 40%–55% of the total material volume; Hydrophilic film-forming polymer materials account for approximately 35%–50% of the total material volume; A regulator used to adjust the water absorption and release properties and dehydration temperature of a material, accounting for approximately 5%–15% of the total material volume.

[0048] In this embodiment, the hydrated salt material can be sodium carbonate decahydrate, the hydrophilic film-forming polymer material can be polyvinyl alcohol and / or sodium carboxymethyl cellulose, and the regulator can be sodium chloride and / or glycerol.

[0049] The humidity buffer layer 3 can be applied to the surface of the heat-conducting layer 5 by coating, casting or composite methods to form a continuously covered humidity buffer structure.

[0050] Example 4: Based on Example 1, this example provides a method for selecting and judging the monitoring indicators of the humidity buffer capacity of the humidity buffer layer 3. Specifically: Hydrated salt materials undergo a hydration reaction after absorbing water, releasing heat. One of their advantages is that they can appropriately slow down the further decrease in surface temperature and prevent the deterioration of condensation conditions.

[0051] During the hydration reaction, the humidity buffer layer 3 exhibits temperature changes, increased conductivity, and an increased dielectric constant. Therefore, the humidity buffer capacity can be monitored by measuring changes in temperature or capacitance. Thus, the sensor can be a temperature sensor, a capacitance sensor, or a combination of both.

[0052] The sensor is placed inside the humidity buffer layer 3. Several sensors can be set along the thickness direction. As the moisture absorption process proceeds, the temperature and capacitance values ​​tend to increase, but the rate of change will show a trend of first increasing and then decreasing. When the upper limit of the moisture absorption capacity is reached, the sensor parameter change rate is 0, and the parameters no longer change, or there is a slight reverse change.

[0053] When the rate of change of the inner sensor parameters is close to 0, it indicates that the capacity of the entire humidity buffer layer 3 is approaching its upper limit.

[0054] Typically, once 1 / 3 to 2 / 3 of the material has completed the hydration reaction, the direct expansion radiant cooling system can be switched to heating mode during off-peak hours. This requires that the surface temperature of the radiant panels be below the air dew point during system operation; otherwise, the moisture absorption is minimal, and no special dehumidification is necessary; the system can simply perform normal oil return circulation.

[0055] For intermittently operating systems, switching can be performed after the system stops operating. If there is no risk of condensation, only oil return circulation will be performed; if there is a risk of condensation, the operating time will be extended according to the dehumidification requirements.

[0056] For continuously operating systems, switching should be performed during low-load periods. Before switching, the room temperature should be appropriately lowered to offset the impact of the heating cycle, while the independent air dehumidification system should remain operational.

[0057] Determining when the dehumidification process is complete: This can also be determined based on changes in temperature or capacitance. During the dehydration process, heat is absorbed, and the dielectric constant decreases. After switching to heating mode, the temperature will initially rise due to heating. Once the heat transfer process reaches equilibrium, dehydration will cause a decrease in both temperature and capacitance. Similarly, when the rate of change approaches 0, it indicates that the dehumidification process is nearing completion.

[0058] Example 5: A method for preventing condensation using the direct expansion radiant cooling terminal described in the above examples, comprising a humidity buffering stage and a humidity buffer layer regeneration stage. During radiant cooling operation, when the surface temperature of the direct expansion radiant cooling terminal approaches or reaches the condensation condition, the humidity buffer layer 3 passively buffers the condensate. The humidity buffer layer 3 absorbs, temporarily stores, and diffuses the condensate on the surface of the direct expansion radiant cooling terminal, thereby delaying the formation of visible condensation. When the sensor detects that the humidity buffering capacity of the humidity buffer layer 3 is close to a preset threshold, the direct expansion radiant cooling system is switched to heating operation mode. The refrigerant condensation releases heat to evaporate and remove the moisture in the humidity buffer layer 3, regenerating the humidity buffer layer 3 in situ. The duration of the heating operation mode is determined based on the sensor monitoring results, continuing until the humidity buffer layer 3 is fully regenerated.

[0059] This invention combines passive humidity buffering with active regeneration under limited conditions to achieve delayed condensation on the terminal surface, optimized system operation stability, and improved radiative cooling capacity, while taking into account both energy efficiency and reliability.

[0060] Example 6: A direct expansion radiant cooling system, including the direct expansion radiant cooling terminal in the above examples.

Claims

1. A direct expansion type radiant cooling terminal, characterized in that, include: substrate; A thermally conductive layer is disposed on the side of the substrate facing the interior. A humidity buffer layer is disposed on the side of the thermally conductive layer away from the substrate; The flow channel is located on the side of the heat-conducting layer away from the humidity buffer layer, and the refrigerant directly evaporates and exchanges heat within the flow channel; A sensor, installed within the humidity buffer layer, is used to monitor the temperature or capacitance of the humidity buffer layer and send the monitoring results to the controller. The humidity buffer layer is made of a material that can absorb, temporarily store, and diffuse condensate. During radiant cooling operation, the humidity buffer layer absorbs, temporarily stores, and diffuses surface condensate to delay the formation of visible condensation. Furthermore, in heating operation mode, the heat released by the condensation of the refrigerant can evaporate and remove the moisture in the humidity buffer layer.

2. The direct expansion radiant cooling terminal as described in claim 1, characterized in that, The substrate has a mounting groove adapted to the flow channel on the side facing the interior. A heat-equalizing layer is provided on the surface of the substrate facing the interior and the inner wall of the mounting groove. The heat-equalizing layer is used to uniformly distribute the cold energy generated by the flow channel laterally.

3. The direct expansion radiant cooling terminal as described in claim 1, characterized in that, The humidity buffer layer is made of a material with hydrophilicity and water storage capacity, which temporarily stores surface condensate through capillary absorption, physical adsorption or chemical bonding.

4. A direct expansion radiant cooling terminal as described in claim 3, characterized in that, The humidity buffer layer contains an inorganic material capable of undergoing a reversible hydration-dehydration reaction with water.

5. A direct expansion radiant cooling terminal as described in claim 4, characterized in that, The inorganic material is a hydrated salt material.

6. A direct expansion radiant cooling terminal as described in claim 1, characterized in that, The humidity buffer layer also includes an adhesive or a porous carrier.

7. A direct expansion radiant cooling terminal as described in claim 1, characterized in that, The flow channel is a capillary structure or a microchannel structure.

8. A direct expansion radiant cooling terminal as described in claim 1, characterized in that, The thermal resistance of the heat-conducting layer should ensure that, under normal radiant cooling conditions, the surface temperature of the humidity buffer layer and the direct expansion radiant cooling terminal is not lower than the dew point temperature; when operating under heating conditions, the heat-conducting layer transfers condensation heat to promote the regeneration of the humidity buffer layer.

9. A method for preventing condensation using the direct expansion radiant cooling terminal according to any one of claims 1-8, characterized in that: During the operation of radiant cooling, the condensate on the surface of the direct expansion radiant cooling terminal is absorbed, temporarily stored and diffused through the humidity buffer layer; when the sensor detects that the humidity buffer capacity of the humidity buffer layer is close to the threshold, the direct expansion radiant cooling system switches to the heating operation mode and regenerates the humidity buffer layer in situ.

10. A direct expansion radiant cooling system, characterized in that, Includes the direct expansion radiant cooling terminal as described in any one of claims 1-8.

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