Heat recovery unit and control method thereof

Abstract

The application provides a heat recovery unit and a control method thereof. The heat recovery unit comprises: a fresh air unit (1) having a fresh air outlet; and a supply air assembly comprising a heat recovery device (2), the heat recovery device (2) comprising a pre-cooling section (3) and a surface cooler (4) arranged in sequence along a supply air direction, the pre-cooling section (3) being arranged at the fresh air outlet, and the cooling liquid in the surface cooler (4) being cooled by heat exchange with air and then entering the pre-cooling section (3) to pre-cool the air flowing through the pre-cooling section (3). According to the heat recovery unit, the energy utilization efficiency of the heat recovery unit can be improved, and the energy consumption can be greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of air conditioning system technology, and more specifically, to a heat recovery unit and its control method. Background Technology

[0002] Currently, air handling units used in data center ventilation and air conditioning systems primarily meet the environmental temperature and humidity requirements of the data center's main control room, ensuring the necessary temperature and humidity conditions for equipment operation and the comfort requirements of control room staff. The common practice in the market is to add electric heating after the surface cooler to reduce the relative humidity of the supply air and achieve the desired human comfort and environmental temperature and humidity. However, this method wastes the heat absorbed by the surface cooler and consumes additional electricity, significantly increasing energy consumption. Summary of the Invention

[0003] The main objective of this invention is to provide a heat recovery unit and its control method, which can improve the energy utilization efficiency of the heat recovery unit and significantly reduce energy consumption.

[0004] To achieve the above objectives, according to one aspect of the present invention, a heat recovery unit is provided, comprising:

[0005] The fresh air handling unit has a fresh air outlet;

[0006] The air supply assembly includes a heat recovery device, which includes a precooling section and a surface cooler arranged sequentially along the air supply direction. The precooling section is located at the fresh air outlet. The coolant in the surface cooler exchanges heat with the air and then enters the precooling section to precool the air flowing through the precooling section.

[0007] Furthermore, the heat recovery device also includes a reheat section, which is located downstream of the air supply direction of the surface cooler. The coolant in the precooling section exchanges heat with the air and then enters the reheat section to heat the air flowing through the reheat section.

[0008] Furthermore, the heat recovery device also includes a cooling unit, in which the coolant flows sequentially through the surface cooler, the precooling section and the reheating section before returning to the cooling unit.

[0009] Furthermore, the heat recovery device also includes a cooling unit and a water pump. The cooling unit forms a circulation loop with the surface cooler through an inlet pipe and a return pipe. A bypass pipe is installed on the return pipe. The bypass pipe is connected to the precooling section and the reheating section in sequence and then connected to the cooling unit. The return pipe can be selectively connected to the bypass pipe or the cooling unit. The water pump provides power for the flow of coolant.

[0010] Furthermore, the return pipe, bypass pipe, and cooling unit are connected by a three-way valve, and a flow regulating valve is installed on the return pipe.

[0011] Furthermore, the air supply assembly also includes a hot water coil, which is located downstream of the air supply direction of the heat recovery unit.

[0012] Furthermore, the air supply assembly also includes an electric heater, which is located downstream of the air supply direction of the heat recovery unit.

[0013] Furthermore, the air supply assembly also includes a humidifier, which is located downstream of the air supply direction of the heat recovery unit.

[0014] Furthermore, the air supply assembly also includes a hot water coil, an electric heater, and a humidifier, which are arranged sequentially downstream of the heat recovery device along the air supply direction.

[0015] Furthermore, the fresh air unit includes a heat recovery section, where fresh air exchanges heat with return air before being blown out from the fresh air outlet.

[0016] According to another aspect of the present invention, a control method for the above-described heat recovery unit is provided, comprising:

[0017] Obtain the current supply air temperature Tsupply and the target supply air temperature Tset;

[0018] Get the current outlet air humidity d_supplied and the target outlet air humidity d_set;

[0019] Compare the current outlet air temperature Tsupply with the target outlet air temperature Tset, and the current outlet air moisture content dsupply with the target outlet air moisture content dset.

[0020] The heat recovery device is adjusted based on the comparison results.

[0021] Furthermore, the steps for adjusting the heat recovery device based on the comparison results include:

[0022] Detect the difference between the current outlet air moisture content dsupply and the target outlet air moisture content dset;

[0023] When |d_send-d_set| ≤ a, the flow control valve remains stationary.

[0024] When |d_send - d_set| > a, the opening of the flow regulating valve is controlled by a PID algorithm based on the current outlet air humidity d_send and the target outlet air humidity d_set.

[0025] Furthermore, the steps for adjusting the heat recovery device based on the comparison results include:

[0026] Detect the difference between the current supply air temperature Tsupply and the target supply air temperature Tset;

[0027] When |T_send-T_set| ≤ b, the three-way valve remains stationary.

[0028] When |T_send - T_set| > b, the opening of the three-way valve is controlled according to the current outlet air temperature T_send and the target outlet air temperature T_set.

[0029] Furthermore, when |Tsend - Tset| > b, the steps for controlling the opening of the three-way valve using a PID algorithm based on the current outlet air temperature Tsend and the target outlet air temperature Tset include:

[0030] When T_send > T_set + b, reduce the bypass opening of the three-way valve until |T_send - T_set| ≤ b;

[0031] When Tsend < Tset-b, increase the bypass opening of the three-way valve;

[0032] Check if Tsend < Tset - b. If so, check if the bypass opening reaches 100%.

[0033] If the opening reaches 100%, then the electric heating is turned on until |T_send-T_set| ≤ b is satisfied;

[0034] If the opening degree is not 100%, continue to increase the bypass opening degree of the three-way valve.

[0035] According to the technical solution of this invention, the heat recovery unit includes: a fresh air unit with a fresh air outlet; and an air supply assembly including a heat recovery device. The heat recovery device includes a pre-cooling section and a surface cooler arranged sequentially along the air supply direction. The pre-cooling section is located at the fresh air outlet. The coolant in the surface cooler exchanges heat with the air and then enters the pre-cooling section to pre-cool the air flowing through it. The air supply assembly of this heat recovery unit includes a heat recovery device that uses the surface cooler to cool and dehumidify the air, regulating its humidity. The pre-cooling section reuses the coolant after heat exchange with the surface cooler, pre-cooling the air upstream of the surface cooler in the air supply direction. This reduces the load on the surface cooler during air handling, fully utilizes the cooling capacity of the coolant after cooling and dehumidifying, effectively improves the energy utilization efficiency of the heat recovery unit, and significantly reduces energy consumption. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 A schematic diagram of the structure of a heat recovery unit according to an embodiment of the present invention is shown; and

[0038] Figure 2 A control principle diagram of a heat recovery unit according to an embodiment of the present invention is shown.

[0039] The above figures include the following reference numerals:

[0040] 1. Fresh air handling unit; 2. Heat recovery device; 3. Pre-cooling section; 4. Surface cooler; 5. Reheat section; 6. Cooling unit; 7. Return pipe; 8. Bypass pipe; 9. Three-way valve; 10. Flow regulating valve; 11. Hot water coil; 12. Electric heater; 13. Humidifier; 14. Heat recovery section; 15. Water pump; 16. Air supply device; 17. Liquid inlet pipe. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] See Figure 1 As shown, according to an embodiment of the present invention, the heat recovery unit includes: a fresh air unit 1 having a fresh air outlet; and an air supply assembly including a heat recovery device 2. The heat recovery device 2 includes a precooling section 3 and a surface cooler 4 arranged sequentially along the air supply direction. The precooling section 3 is located at the fresh air outlet. The coolant in the surface cooler 4 exchanges heat with the air and then enters the precooling section 3 to precool the air flowing through the precooling section 3.

[0043] The air supply assembly of the heat recovery unit includes a heat recovery device 2. The heat recovery device 2 uses a surface cooler 4 to cool and dehumidify the air, regulate the air humidity, and reuses the coolant after heat exchange in the surface cooler 4 through the pre-cooling section 3. This pre-cools the air located upstream of the air supply direction of the surface cooler 4, reduces the load on the surface cooler 4 during air handling, and makes full use of the cooling capacity of the coolant after the surface cooler 4 cools and dehumidifies the air, effectively improving the energy utilization efficiency of the heat recovery unit and significantly reducing energy consumption.

[0044] In one embodiment, the heat recovery device 2 further includes a reheat section 5, which is located downstream of the air supply direction of the surface cooler 4. The coolant in the precooling section 3 exchanges heat with the air and then enters the reheat section 5 to heat the air flowing through the reheat section 5.

[0045] In this embodiment, the heat recovery device 2 further includes a reheat section 5, which is connected in series with the precooling section 3. After the precooling section 3 exchanges heat with the fresh air and absorbs the heat from the fresh air, the coolant that has absorbed the heat can flow to the reheat section 5, where a coolant with a temperature higher than the air temperature after being cooled and dehumidified by the surface cooler 4 is formed. This allows the heat absorbed by the coolant in the precooling section 3 to be used to heat the air located downstream of the surface cooler 4 and which has been cooled and dehumidified by the surface cooler 4. Since the precooling section 3 precools the air, it is internally cooled. The cooling capacity of the coolant comes from the cooling capacity of the coolant after heat exchange in the surface cooler 4. The heat of the coolant in the reheating section 5, which reheats the air, comes from the heat exchange of the fresh air. Therefore, it can make full use of the energy of the coolant itself and the energy contained in the air, reducing the cooling load of the surface cooler 4 in the process of air handling. At the same time, it can also reduce the heating load of the heater located after the surface cooler 4 for heating the processed air, reduce the sensible heat cooling load of the processed air, greatly reduce or even eliminate the energy consumption of traditional electric heating, and achieve high efficiency and energy saving.

[0046] The precooling section 3 and the reheating section 5 are located on the upstream and downstream sides of the surface cooler 4 and are connected by pipes to form a horseshoe-shaped heat exchange tube, or an integral horseshoe-shaped heat pipe can be used to achieve energy transfer by utilizing the characteristics of the heat pipe itself.

[0047] In one embodiment, the heat recovery device 2 further includes a cooling unit 6 and a water pump 15. The coolant in the cooling unit 6 flows sequentially through the surface cooler 4, the precooling section 3 and the reheating section 5 and then flows back to the cooling unit 6. The water pump 15 provides power for the flow of the coolant.

[0048] In this embodiment, the cooling unit 6 is sequentially connected to the precooling section 3, the surface cooler 4, and the reheating section 5. The water pump 15 can be located at the outlet of the cooling unit 6 to drive the coolant to circulate. During the coolant circulation, the air is first cooled and dehumidified at the surface cooler 4, then flows to the precooling section 3 where the residual coolant precools the air upstream of the surface cooler 4. After absorbing heat from the fresh air at the fresh air outlet and being heated, it flows to the reheating section 5 located downstream of the surface cooler 4 to exchange heat with the air downstream of the surface cooler 4, thus heating the air. In this embodiment, the coolant circulation formed by the cooling unit 6, precooling section 3, surface cooler 4, and reheating section 5 is a single-loop structure, and the air temperature and humidity can be adjusted by regulating the flow control valve 10 on the pipeline.

[0049] In one embodiment, the heat recovery device 2 further includes a cooling unit 6, which forms a circulation loop with the surface cooler 4 through an inlet pipe 17 and a return pipe 7. A bypass pipe 8 is provided on the return pipe 7, which is connected to the precooling section 3 and the reheating section 5 in sequence and then connected to the cooling unit 6. The return pipe 7 can be selectively connected to the bypass pipe 8 or the cooling unit 6.

[0050] The return pipe 7, the bypass pipe 8, and the cooling unit 6 are connected by a three-way valve 9, and a flow regulating valve 10 is installed on the return pipe 7.

[0051] In this embodiment, the three-way valve 9 can regulate the flow rate distributed to the bypass pipe 8, thereby regulating the air temperature. The flow regulating valve 10 can regulate the flow rate of the coolant flowing out of the surface cooler 4, thereby regulating the heat exchange time of the coolant in the surface cooler 4, regulating the surface temperature of the surface cooler 4, and achieving the purpose of regulating the air humidity.

[0052] The process of adjusting the air temperature using the three-way valve 9 is as follows: When the bypass opening of the three-way valve 9 decreases, the amount of coolant entering the precooling section 3 decreases, the amount of coolant exchanging heat with the air decreases, and the amount of air heat that can be absorbed decreases. Therefore, the amount of heat from the coolant entering the reheating section 5 decreases, and the amount of air heated after being cooled and dehumidified by the surface cooler 4 decreases, thus lowering the air temperature after heat exchange in the reheating section 5. When the bypass opening of the three-way valve 9 increases, the amount of coolant entering the precooling section 3 increases, the amount of coolant exchanging heat with the air increases, and the amount of air heat that can be absorbed increases. Therefore, the amount of heat from the coolant entering the reheating section 5 increases, and the amount of air heated after being cooled and dehumidified by the surface cooler 4 increases, thus raising the air temperature after heat exchange in the reheating section 5.

[0053] Through the combined regulation of the three-way valve 9 and the flow regulating valve 10, the indoor air supply temperature and humidity can be precisely controlled, thereby effectively ensuring a constant temperature and humidity indoor environment.

[0054] In one embodiment, the air supply assembly further includes a hot water coil 11, located downstream of the heat recovery device 2 in the air supply direction. The hot water coil 11 can heat the flowing air, thereby adjusting the air outlet temperature.

[0055] In one embodiment, the air supply assembly further includes an electric heater 12 located downstream of the heat recovery device 2 in the air supply direction. The electric heater 12 can heat the flowing air, thereby adjusting the outlet air temperature.

[0056] In one embodiment, the air supply assembly further includes a humidifier 13, located downstream of the heat recovery device 2 in the air supply direction. The humidifier 13 is, for example, an electrode humidifier. The humidifier 13 is often used for indoor humidification in winter to increase the moisture content of the air as it passes through.

[0057] In one embodiment, the air supply assembly further includes a hot water coil 11, an electric heater 12, and a humidifier 13, which are sequentially arranged downstream of the heat recovery device 2 along the air supply direction. The air supply assembly also includes an air supply device 16 located at the air outlet, which includes a fan capable of providing air supply power.

[0058] In one embodiment, the fresh air unit 1 includes a heat recovery section 14, where fresh air exchanges heat with return air in the heat recovery section 14 and is then blown out from the fresh air outlet.

[0059] The fresh air exchanges heat with the return air in the heat recovery section 14, which can fully absorb the cold air, thereby further reducing the cooling load of the surface cooler when processing air and improving the energy utilization efficiency.

[0060] The coolant mentioned above can be water, or other coolants such as ethanol.

[0061] In this embodiment of the invention, the heat recovery unit bypasses a portion of cold water into the heat recovery device 2 by adding a three-way valve 9 to the return pipe 7. When the hot and humid outdoor air passes through the plate-fin heat exchanger in the fresh air unit 1 and is cooled to a temperature of T1 with a relative humidity of H1, the calculated moisture content is d1. Then, it passes through the pre-cooling section 3 of the horseshoe-shaped heat pipe to a temperature of T2 with a relative humidity of H2, and the calculated moisture content is d2. The water in the pre-cooling section 3 of the horseshoe-shaped heat pipe evaporates and absorbs heat. Along the loop from the connecting section to the reheating section 5, the heat is carried away and the cold is transferred. The hot and humid fresh air becomes pre-cooled air. Then, it passes through the surface cooler 4 for dehumidification and further cooling to a temperature of T3 with a relative humidity of H3, and the calculated moisture content is d3. The surface-cooled fresh air then passes through the reheating section 5 of the horseshoe-shaped heat pipe and is heated to a temperature of T4 with a relative humidity of H4, and the calculated moisture content is d4, achieving a comfortable temperature and humidity before being sent indoors. The horseshoe-shaped heat pipe developed by this invention can be used in air conditioning systems to improve the dehumidification effect of the surface cooler and to save energy.

[0062] See also Figure 2 As shown, according to an embodiment of the present invention, the control method of the heat recovery unit includes: acquiring the current outlet air temperature Tsent and the target outlet air temperature Tset; acquiring the current outlet air humidity dsent and the target outlet air humidity dset; comparing the current outlet air temperature Tsent and the target outlet air temperature Tset, as well as the current outlet air humidity dsent and the target outlet air humidity dset; and adjusting the heat recovery device 2 according to the comparison results.

[0063] In one embodiment, the step of adjusting the heat recovery device 2 based on the comparison result includes: detecting the difference between the current outlet air humidity d_sent and the target outlet air humidity d_set; when |d_sent - d_set| ≤ a, then keeping the flow regulating valve inactive; when |d_sent - d_set| > a, then controlling the opening of the flow regulating valve using a PID algorithm based on the current outlet air humidity d_sent and the target outlet air humidity d_set.

[0064] In one embodiment, the step of adjusting the heat recovery device 2 based on the comparison result includes: detecting the difference between the current outlet air temperature Tsent and the target outlet air temperature Tset; when |Tsent - Tset| ≤ b, keeping the three-way valve 9 inactive; when |Tsent - Tset| > b, controlling the opening degree of the three-way valve 9 according to the current outlet air temperature Tsent and the target outlet air temperature Tset.

[0065] In one embodiment, when |Tsend - Tset| > b, the step of controlling the opening of the three-way valve 9 using a PID algorithm based on the current outlet air temperature Tsend and the target outlet air temperature Tset includes: when Tsend > Tset + b, reducing the bypass opening of the three-way valve 9 until |Tsend - Tset| ≤ b; when Tsend < Tset - b, increasing the bypass opening of the three-way valve 9; detecting whether Tsend < Tset - b, and if so, detecting whether the bypass opening reaches 100%;

[0066] If the opening reaches 100%, the electric heating is turned on until |T_send-T_set| ≤ b is met; if the opening does not reach 100%, the bypass opening of the three-way valve 9 is further increased.

[0067] In the above embodiments, a is, for example, 0.5 g / kg, and b is, for example, 1 °C.

[0068] The control method of this embodiment aims to regulate the supply air temperature and supply air moisture content to equal the set values. The set temperature hysteresis value is 1℃, and the set moisture content hysteresis value is 0.5g / kg. That is, if the difference between the supply air moisture content and the set value is within ±0.5g / kg, the flow regulating valve 10 remains unchanged. If the difference between the supply air temperature and the set value is within ±1℃, the bypass opening of the three-way valve 9 remains unchanged.

[0069] If |d_send - d_set| ≤ 0.5 for 10 seconds, the flow regulating valve 10 will not operate; otherwise, the opening of the flow regulating valve 10 will be controlled by a PID algorithm based on the target supply air humidity and the current supply air humidity. The target supply air humidity is the target humidity value, and the feedback temperature is the real-time humidity value. The P, Ti, and Td parameters in the PID control block can be set. If the supply air temperature T_send > the set temperature T_set + 1 for 10 seconds, the bypass opening of the three-way valve 9 will decrease, reducing the water flow. This reduces the amount of cold water flowing into the precooling section 3 and the reheating section 5, decreasing the heat exchange and thus lowering T_send until |T_send - T_set| ≤ 1, at which point the bypass opening of the three-way valve 9 will remain unchanged; conversely, the opposite is also true. If the demand is still not met after the bypass opening of the three-way valve 9 reaches 100%, the electric heater 12 can be turned on to meet the demand.

[0070] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0071] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat recovery unit, characterized in that, include: The fresh air handling unit (1) has a fresh air outlet; The air supply assembly includes a heat recovery device (2), which includes a precooling section (3) and a surface cooler (4) arranged sequentially along the air supply direction. The precooling section (3) is located at the fresh air outlet. The coolant in the surface cooler (4) exchanges heat with the air and then enters the precooling section (3) to precool the air flowing through the precooling section (3). The heat recovery device (2) further includes a reheat section (5), which is located downstream of the air supply direction of the surface cooler (4). The coolant in the precooling section (3) exchanges heat with the air and then enters the reheat section (5) to heat the air flowing through the reheat section (5). The heat recovery device (2) also includes a cooling unit (6) and a water pump (15). The coolant in the cooling unit (6) flows through the surface cooler (4), the precooling section (3) and the reheating section (5) in sequence and then flows back to the cooling unit (6). The water pump (15) provides power for the flow of the coolant. The heat recovery device (2) also includes a cooling unit (6), which forms a circulation loop with the surface cooler (4) through an inlet pipe (17) and a return pipe (7). A bypass pipe (8) is provided on the return pipe (7), which is connected to the precooling section (3) and the reheating section (5) in sequence and then connected to the cooling unit (6). The return pipe (7) can be selectively connected to the bypass pipe (8) or the cooling unit (6). The return pipe (7), the bypass pipe (8) and the cooling unit (6) are connected by a three-way valve (9), and a flow regulating valve (10) is provided on the return pipe (7).

2. The heat recovery unit according to claim 1, characterized in that, The air supply assembly also includes a hot water coil (11), which is located downstream of the air supply direction of the heat recovery device (2).

3. A control method for a heat recovery unit as described in claim 1 or 2, characterized in that, include: Obtain the current supply air temperature Tsupply and the target supply air temperature Tset; Get the current outlet air humidity d_supplied and the target outlet air humidity d_set; Compare the current outlet air temperature Tsupply with the target outlet air temperature Tset, and the current outlet air moisture content dsupply with the target outlet air moisture content dset. The heat recovery device (2) is adjusted according to the comparison results.

4. The control method for the heat recovery unit according to claim 3, characterized in that, The steps for adjusting the heat recovery device (2) based on the comparison results include: Detect the difference between the current outlet air moisture content dsupply and the target outlet air moisture content dset; When |d_send-d_set| ≤ a, the flow control valve remains stationary. When |d_send - d_set| > a, the opening of the flow regulating valve is controlled by a PID algorithm based on the current outlet air humidity d_send and the target outlet air humidity d_set.

5. The control method for the heat recovery unit according to claim 3, characterized in that, The steps for adjusting the heat recovery device (2) based on the comparison results include: Detect the difference between the current supply air temperature Tsupply and the target supply air temperature Tset; When |T_send-T_set| ≤ b, keep the three-way valve (9) from operating; When |T_send-T_set| > b, control the opening degree of the three-way valve (9) according to the current outlet air temperature T_send and the target outlet air temperature T_set.

6. The control method for the heat recovery unit according to claim 5, characterized in that, When |T_send-T_set| > b, the steps for controlling the opening of the three-way valve (9) using a PID algorithm based on the current outlet air temperature T_send and the target outlet air temperature T_set include: When T_send > T_set + b, reduce the bypass opening of the three-way valve (9) until |T_send - T_set| ≤ b; When Tsend < Tset-b, increase the bypass opening of the three-way valve (9); Check if Tsend < Tset - b; if so, check if the bypass opening reaches 100%. If the opening reaches 100%, then the electric heating is turned on until |T_send-T_set| ≤ b is satisfied; If the opening degree does not reach 100%, the bypass opening degree of the three-way valve (9) is further increased.

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