A dual heat recovery DOAS air conditioner, system and control method

Abstract

The present invention relates to the technical field of air conditioning, and discloses a dual heat recovery type DOAS air conditioner, system and control method, comprising a chiller, a condensation heat recovery device, a cooling tower, an indoor exhaust heat recovery device, a fresh air unit, an air mixing box and a fan coil unit. A part of the condensation heat of the chiller is recovered and used to heat the return water of the fresh air unit to make it higher than the indoor dew point temperature, thereby avoiding the energy consumption of terminal chilled water reheating, reducing the cooling water inlet temperature of the chiller, and improving the overall energy efficiency of the system. The water temperature control of the condensation heat recovery avoids condensation at the terminal, pre-cools the hot and humid outdoor fresh air, and reduces the fresh air cooling load. The mixing ratio of the fresh air and the bypass fresh air is processed by the air valve control, thereby controlling the moisture content of the fresh air supply, and supplemented by the adjustment of the fresh air volume, realizing the humidity control of the terminal room by the fresh air unit. The fan coil unit realizes the control of the sensible heat exchange amount by adjusting the size of the circulating air volume, thereby achieving the purpose of accurately controlling the room temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a dual heat recovery type DOAS air conditioning, system and control method. Background Art

[0002] Building operating energy consumption in my country accounts for approximately 21% of the nation's total energy consumption, and air conditioning systems account for approximately 50% of this energy consumption. Energy-efficient operation of air conditioning systems has become a key component of energy conservation and emission reduction in my country. However, the energy efficiency of my country's current air conditioning systems remains relatively low, with some refrigeration rooms achieving an actual annual energy efficiency ratio (EER) of 2.5-3.0. This compares to ASHRAE, the American Society of Refrigeration, which stipulates that high-efficiency refrigeration rooms should have an EER of at least 5.0.

[0003] According to statistics, people spend approximately 90% of their lives indoors. A good indoor environment plays a vital role in physical and mental health. However, my country currently faces serious indoor air pollution. According to a survey, indoor air pollution causes 111,000 excess deaths and 4.3 million excess emergency room visits each year in my country, resulting in direct and indirect economic losses of US$10.7 billion (approximately over 70 billion RMB).

[0004] Compared with other air conditioning systems, dedicated outdoor air systems (DOAS) are increasingly popular due to their advantages, such as improving indoor air quality and reducing building operating energy consumption. Conventional DOAS often use a single-cold-source series water supply method, where the low-temperature outlet water from a single-temperature chiller is first supplied to the outdoor air unit, and the high-temperature return water from the outdoor air unit serves as the inlet water for the terminal equipment. When the inlet water temperature of the terminal equipment is lower than the indoor air dew point, it requires further treatment to raise it above the dew point to prevent condensation on the terminal equipment. This cascaded energy utilization method makes DOAS highly energy-efficient. Furthermore, the independent temperature and humidity control method, which controls humidity in the outdoor air unit and temperature in the terminal equipment, enables more precise control of indoor temperature and humidity.

[0005] However, due to the limitations of system design and control strategies, conventional DOAS have great energy-saving potential and are more prone to terminal condensation problems. For example, conventional DOAS use a mixed water method to control the terminal inlet water temperature to prevent condensation on the terminal equipment. This method is limited by the minimum frequency of the water pump, resulting in low control accuracy. At the same time, it increases the number of water pumps and adds additional energy consumption. Another method for controlling the terminal inlet water temperature is water temperature control, which uses heating to increase the terminal inlet water temperature. This method has high control accuracy but suffers from low energy efficiency due to the offset of cold and heat. How to improve the control accuracy of the terminal anti-condensation inlet water temperature while improving the system energy efficiency is a major issue facing existing DOAS.

[0006] The prior art discloses a variable-frequency household fresh air purification full air conditioning system, primarily consisting of a fresh air purification processor and a variable-frequency air-cooled hot / cold water heater. In the fresh air purification processor, fresh air and return air are mixed in a mixing section, filtered through a coarse-effect filter, and then heat-exchanged and dehumidified with chilled / cooled water in a surface heat exchanger. After passing through a high-efficiency filter, the air is then delivered to the room through the air supply vent. This invention achieves miniaturization of central air conditioning and, by regulating temperature, humidity, CO2 concentration, and PM2.5, maximizes a healthy and comfortable indoor environment year-round while improving energy efficiency. During transitional seasons, even without turning on the cooling unit, the system can filter the air and adjust the fresh air ratio and blower speed based on indoor PM2.5 and CO2 concentrations to ensure adequate indoor ventilation during these transitional seasons. This addresses the gap in traditional air conditioning systems that do not regulate the indoor environment during these transitional seasons. Furthermore, the system can be integrated with a mobile phone app to enable remote parameter monitoring and control. This prior art suffers from the problem of condensation at the end of the unit. Summary of the Invention

[0007] The purpose of the present invention is to provide a dual heat recovery DOAS air conditioner, system and control method to avoid terminal condensation and improve the overall energy efficiency of the system.

[0008] In order to achieve the above-mentioned objectives, the present invention provides a dual heat recovery type DOAS air conditioner, including a chiller, a condensing heat recovery device, a cooling tower, an indoor exhaust heat recovery device, a fresh air unit, an air mixing box and a fan coil unit. The water outlet of the chiller is connected to the water inlet of the cooling tower and the fresh air unit, the water outlet of the cooling tower and the fresh air unit is connected to the water inlet of the condensing heat recovery device, the water outlet of the condensing heat recovery device is connected to the water inlet of the chiller and the fan coil unit, the water outlet of the fan coil unit is connected to the water inlet of the chiller, the outdoor fresh air is connected to the air inlet of the fresh air unit, the air outlet of the fresh air unit is connected to the air inlet of the mixing box, the air outlet of the mixing box is connected to the air inlet of the room, the air outlet of the room is connected to the air inlet of the indoor exhaust heat recovery device, the air outlet of the indoor exhaust heat recovery device is connected to the outdoors, the air outlet of the room is connected to the air inlet of the fan coil unit, and the air outlet of the fan coil unit is connected to the air inlet of the room.

[0009] Preferably, a fresh air surface cooler and a fresh air fan are provided at the fresh air unit, the water outlet of the chiller is connected with the water inlet of the fresh air surface cooler of the fresh air unit, the water outlet of the fresh air surface cooler is connected with the water inlet of the condensing heat recovery device, the outdoor fresh air is connected with the air inlet of the fresh air surface cooler of the fresh air unit, and is connected with the air inlet of the mixing box through the drive of the fresh air fan.

[0010] Preferably, it also includes a terminal air reheater, and the air discharged from the air outlet of the air mixing box passes through the terminal air reheater and then enters the room.

[0011] Preferably, an exhaust fan is further included, and the air outlet of the indoor exhaust heat recovery device is connected to the outdoors through the exhaust fan.

[0012] Preferably, it also includes a cooling water pump and a chilled water pump, the water outlet of the condensing heat recovery device is connected to the water inlet of the chiller through the cooling water pump, and the water outlet of the fan coil is connected to the water inlet of the chiller through the chilled water pump.

[0013] Preferably, an expansion water tank is further included, and the expansion water tank is connected to the water inlet of the chilled water pump.

[0014] Preferably, it also includes a temperature sensor, a humidity sensor, and a flow sensor. The temperature sensor is arranged in the room, at the water inlet and outlet of the chiller, at the water outlet of the condensing heat recovery device, at the water outlet of the cooling tower, at the air inlet of the indoor exhaust heat recovery device, and at the air inlet of the room. The humidity sensor is arranged in the room. The flow sensor is arranged at the water inlet of the chiller, at the air outlet of the fresh air fan, and at the fresh air duct at the end of the room.

[0015] The present invention also provides a dual heat recovery DOAS air conditioning system, comprising a chilled water loop, a cooling water loop, a fresh exhaust air loop and an indoor circulating air loop;

[0016] The chilled water loop includes a chiller, fresh air surface cooler, condensing heat recovery device, terminal heat exchange equipment and chilled water pump;

[0017] The cooling water loop includes a chiller, cooling tower, condensing heat recovery device and cooling water pump;

[0018] The fresh air exhaust loop includes indoor exhaust air heat recovery device, fresh air surface cooler, fresh air fan, terminal air reheater and exhaust fan;

[0019] The indoor circulating air loop includes fan coil units and terminal air reheaters.

[0020] The present invention also provides a dual heat recovery DOAS air conditioning control method, including chilled water main bypass valve control, condensing heat recovery regulating valve control, terminal three-way water valve control, fresh air fan control, exhaust fan control, fresh air unit bypass air valve and fresh air unit air valve control, terminal fresh air valve control, fan coil built-in fan control, terminal air reheater control and indoor exhaust heat recovery device control;

[0021] The chilled water main bypass valve is controlled as follows: when the maximum temperature of the terminal room is lower than the indoor set temperature, that is, when the cooling capacity is oversupplied, the chilled water main bypass valve is opened and the maximum temperature of the terminal room is raised to near the set temperature by adjusting the opening;

[0022] The condensing heat recovery regulating valve control is specifically to adjust the opening of the condensing heat recovery regulating valve according to the deviation between the set value and the actual value of the fan coil water inlet temperature, so that the actual water inlet temperature is controlled above the indoor dew point temperature;

[0023] The terminal three-way water valve control specifically adjusts the opening of the terminal three-way water valve when the room temperature is lower than the indoor set temperature, so that all the chilled water bypasses back to the chiller to avoid overcooling of the room;

[0024] The control of the fresh air fan and the exhaust fan is to adjust the speed of the fresh air fan according to the deviation between the total fresh air volume set value and the actual value, so that the actual total fresh air volume is controlled near the set total fresh air volume. The exhaust fan speed needs to be controlled according to the indoor set pressure to maintain a certain indoor positive pressure.

[0025] The air valve control of the fresh air unit is specifically to adjust the opening of the air valve of the fresh air unit according to the deviation between the actual average relative humidity of each room and the set relative humidity, thereby adjusting the mixing ratio of the processed fresh air and the bypass fresh air, thereby controlling the moisture content of the fresh air supply and ultimately achieving the purpose of controlling the relative humidity of the room;

[0026] The terminal fresh air valve control specifically adjusts the opening of the terminal fresh air valve according to the deviation between the terminal fresh air volume set value and the actual value, so that the actual fresh air volume is controlled near the set fresh air volume;

[0027] The built-in fan control of the fan coil unit specifically adjusts the terminal circulation air volume according to the deviation between the indoor temperature set value and the actual value, so that the actual indoor temperature is controlled near the set temperature;

[0028] The terminal air reheater control is to open the terminal air reheater when the room temperature is too cold, so that the room temperature returns to the reheating set temperature;

[0029] The indoor exhaust heat recovery device is controlled as follows: when the outdoor dry-bulb temperature is higher than the indoor return air temperature, the indoor exhaust heat recovery device is turned on to pre-cool the hot and humid outdoor fresh air; when the outdoor dry-bulb temperature is lower than the indoor return air temperature, the indoor exhaust heat recovery device is turned off, and at this time all the outdoor fresh air is bypassed to the fresh air unit.

[0030] Preferably, in the control of the condensing heat recovery regulating valve, when the heat transfer temperature difference is considered, the actual water inlet temperature can be slightly lower than the indoor air dew point temperature by about 3°C; in the control of the fresh air fan, the total fresh air volume must not only meet the minimum total fresh air volume requirements, but also meet the dehumidification requirements of the terminal room; the terminal fresh air valve control requires that the set value of the terminal fresh air volume is not lower than the minimum fresh air volume of the room.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The system's dual heat recovery links include condensation heat recovery and indoor exhaust heat recovery. In the condensation heat recovery link, when the return water temperature of the fresh air unit is lower than the indoor dew point temperature at the terminal, a portion of the condensation heat of the chiller is recovered and used to heat the return water of the fresh air unit to above the indoor dew point temperature. Condensation heat recovery avoids the energy consumption of terminal chilled water reheating on the one hand, and reduces the cooling water inlet temperature of the chiller on the other hand, thereby greatly improving the overall energy efficiency of the system. In addition, the water temperature control method of condensation heat recovery has high control accuracy and can effectively avoid the problem of condensation at the terminal. The indoor exhaust heat recovery link pre-cools the hot and humid outdoor fresh air, thereby reducing the fresh air cooling load and further improving the system energy efficiency. The fresh air unit controls the mixing ratio of fresh air and bypass fresh air through air valve control, thereby controlling the moisture content of the fresh air supply. At the same time, the adjustment of the fresh air volume effectively realizes the humidity control of the terminal room by the fresh air unit. The fan coil unit controls the sensible heat exchange by adjusting the circulating air volume, thereby achieving the purpose of accurately controlling the room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of a dual heat recovery DOAS air conditioner according to an embodiment of the present invention;

[0034] Figure 2 This is a module diagram of a dual heat recovery DOAS air conditioning system according to an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of the control method of the dual heat recovery DOAS air conditioner according to an embodiment of the present invention.

[0036] In the figure, 1. Chiller; 2. Cooling water pump; 3. Chilled water pump; 4. Expansion water tank; 5. Chilled water main bypass valve; 6. Condensation heat recovery device; 7. Cooling tower; 8. Condensation heat recovery regulating valve; 9. Terminal fresh air valve; 10. Temperature sensor; 11. Humidity sensor; 12. Exhaust fan; 13. Indoor exhaust heat recovery device; 14. Fresh air unit bypass air valve; 15. Fresh air unit air valve; 16. Fresh air unit; 17. Fresh air surface cooler; 18. Fresh air fan; 19. Flow sensor; 20. Mixing box; 21. Terminal air reheater; 22. Fan coil unit; 23. Terminal three-way water valve; 24. Room; 25. Outdoor; 26. Outdoor fresh air. DETAILED DESCRIPTION

[0037] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0041] Example 1

[0042] like Figure 1As shown, a dual heat recovery DOAS air conditioner of a preferred embodiment of the present invention includes a chiller 1, a condensing heat recovery device (water-water partition heat exchanger) 6, a cooling tower 7, an indoor exhaust heat recovery device 13, a fresh air unit 16, an air mixing box 20 and a fan coil 22. The water outlet of the chiller 1 is connected to the water inlet of the cooling tower 7 and the fresh air unit 16, the water outlet of the cooling tower 7 and the fresh air unit 16 is connected to the water inlet of the condensing heat recovery device 6, and the water outlet of the condensing heat recovery device 6 is connected to the water inlet of the chiller 1 and the fan coil 22. The water outlet of the fan coil unit 22 is connected to the water inlet of the chiller 1, the outdoor fresh air 26 is connected to the air inlet of the fresh air unit 16, the air outlet of the fresh air unit 16 is connected to the air inlet of the air mixing box 20, the air outlet of the air mixing box 20 is connected to the air inlet of the room 24, the air outlet of the room 24 is connected to the air inlet of the indoor exhaust heat recovery device 13, the air outlet of the indoor exhaust heat recovery device 13 is connected to the outdoor 25, the air outlet of the room 24 is connected to the air inlet of the fan coil unit 22, and the air outlet of the fan coil unit 22 is connected to the air inlet of the room 24.

[0043] A fresh air surface cooler 17 and a fresh air fan 18 are provided at the fresh air unit 16. The water outlet of the chiller 1 is connected to the water inlet of the fresh air surface cooler 17 of the fresh air unit 16. The water outlet of the fresh air surface cooler 17 is connected to the water inlet of the condensing heat recovery device 6. The outdoor fresh air 26 is connected to the air inlet of the fresh air surface cooler 17 of the fresh air unit 16, and is connected to the air inlet of the mixing box 20 through the drive of the fresh air fan 18.

[0044] This embodiment further includes a terminal air reheater 21 , and the air discharged from the air outlet of the air mixing box 20 passes through the terminal air reheater 21 and then enters the room 24 .

[0045] This embodiment further includes an exhaust fan 12 , and an air outlet of the indoor exhaust heat recovery device 13 is connected to the outside 25 through the exhaust fan 12 .

[0046] This embodiment also includes a cooling water pump 2 and a chilled water pump 3. The water outlet of the condensing heat recovery device 6 is connected to the water inlet of the chiller 1 through the cooling water pump 2, and the water outlet of the fan coil 22 is connected to the water inlet of the chiller 1 through the chilled water pump 3.

[0047] This embodiment further includes an expansion water tank 4 , which is communicated with the water inlet of the chilled water pump 3 .

[0048] This embodiment also includes a temperature sensor 10, a humidity sensor 11, and a flow sensor 19. The temperature sensor 10 is arranged in the room 24, at the water inlet and outlet of the chiller 1, the water outlet of the condensing heat recovery device 6, the water outlet of the cooling tower 7, the air inlet of the indoor exhaust heat recovery device 13, and the air inlet of the room 24. The humidity sensor 11 is arranged in the room 24. The flow sensor 19 is arranged at the water inlet of the chiller 1, the air outlet of the fresh air fan 18, and the fresh air duct at the end of the room 24.

[0049] Example 2

[0050] like Figure 2 As shown, the present invention also provides a dual heat recovery DOAS air conditioning system, including a chilled water loop, a cooling water loop, a fresh exhaust air loop and an indoor circulating air loop;

[0051] The chilled water loop includes the chiller 1, fresh air surface cooler 17, condensing heat recovery device 6, terminal heat exchange equipment and chilled water pump 3 and other main equipment;

[0052] The cooling water loop includes the main equipment such as the chiller 1, cooling tower 7, condensing heat recovery device 6 and cooling water pump 2;

[0053] The fresh air exhaust loop includes the indoor exhaust air heat recovery device 13, fresh air surface cooler 17, fresh air fan 18, terminal air reheater 21 and exhaust fan 12 and other main equipment;

[0054] The indoor circulating air loop includes main equipment such as fan coil units 22 and terminal air reheaters 21.

[0055] It is worth noting that the loops are coupled and included with each other, and through coordinated control, they jointly maintain stable indoor air parameters.

[0056] Take the double heat recovery DOAS air conditioning system with fan coil as the terminal heat exchange equipment as an example:

[0057] like Figure 1 As shown in the figure, the dual heat recovery DOAS air-conditioning system consists of four loops: chilled water loop (1-17-6-22-3-1), cooling water loop (1-7-6-2-1), fresh exhaust air loop (26-13-16-17-18-20-21-24-13-12-25), and indoor circulating air loop (24-22-20-21-24).

[0058] Chilled water loop process: The low-temperature chilled water outlet of the chiller 1 is sent to the fresh air surface cooler 17 of the fresh air unit 16. The return water of the fresh air surface cooler 17 is sent to the condensing heat recovery device 6. The chilled water return water of the condensing heat recovery device 6 is sent to the fan coil 22. The high-temperature chilled water return water of the fan coil 22 is sent back to the chiller 1 via the chilled water pump 3.

[0059] Cooling water loop process: The high-temperature cooling water outlet of the chiller 1 is sent to the cooling tower 7, the cooling water return from the cooling tower is sent to the condensing heat recovery device 6, and the low-temperature cooling water return from the condensing heat recovery device 6 is sent back to the chiller 1 through the cooling water pump 2;

[0060] Fresh air circulation process: outdoor fresh air 26 passes through the indoor exhaust heat recovery device 13 and is sent to the fresh air surface cooler 17 of the fresh air unit 16. Driven by the fresh air fan 18, it is mixed with the indoor return air in the air mixing box 20, and then passes through the terminal air reheater 21 and is sent to the room 24. Finally, driven by the exhaust fan 12, it passes through the indoor exhaust heat recovery device 13 and is discharged to the outside 25.

[0061] Indoor air circulation loop process: Indoor air is driven by the built-in fan of fan coil unit 22, passes through the built-in heat exchanger of fan coil unit 22, and is delivered to air mixing box 20, where it is mixed with processed outdoor fresh air and delivered to room 24. It is worth noting that when fan coil unit 22 is installed in a radiant ceiling, radiant wall, radiant floor, etc., the fan configuration can be omitted.

[0062] Example 3

[0063] like Figure 3 As shown, the present invention also provides a dual heat recovery DOAS air conditioning control method, which is highly practical, has high application value, and is highly robust, including control of the chilled water main bypass valve 5, the condensing heat recovery regulating valve 8, the terminal three-way water valve 23, the fresh air fan 18, the exhaust fan 12, the fresh air unit air valve 15, the terminal fresh air valve 9, the built-in fan of the fan coil 22, the terminal air reheater 21, and the indoor exhaust heat recovery device 13;

[0064] The bypass valve 5 of the chilled water main is controlled to achieve a balance between supply and demand and reduce the energy consumption of the pipe network. When the maximum temperature of the terminal room 24 is lower than the indoor set temperature, it is in a state of oversupply of cooling capacity. At this time, the bypass valve 5 of the chilled water main is opened and the opening is adjusted to bring the maximum temperature of the terminal room 24 back to near the set temperature.

[0065] The condensing heat recovery regulating valve 8 is controlled specifically by adjusting the opening of the condensing heat recovery regulating valve 8 according to the deviation between the set value and the actual value of the inlet water temperature of the fan coil 22, so that the actual inlet water temperature is controlled above the indoor dew point temperature;

[0066] The terminal three-way water valve 23 is controlled specifically to adjust the opening of the terminal three-way water valve 23 when the temperature of the room 24 is lower than the indoor set temperature, so that all the chilled water is bypassed back to the chiller 1 to avoid overcooling of the room 24;

[0067] The control of the fresh air fan 18 and the exhaust fan 12 is specifically to adjust the speed of the fresh air fan 18 according to the deviation between the total fresh air volume set value and the actual value, so that the actual total fresh air volume is controlled near the set total fresh air volume, and the exhaust fan 12 needs to be controlled according to the indoor set pressure to maintain a certain indoor positive pressure.

[0068] The control of the bypass ventilation valve 14 and the fresh air unit air valve 15 of the fresh air unit is specifically to adjust the opening of the bypass ventilation valve 14 and the fresh air unit air valve 15 according to the deviation between the actual average relative humidity of each room and the set relative humidity, thereby adjusting the mixing ratio of the processed fresh air and the bypass fresh air, thereby achieving the moisture content control of the fresh air supply, and ultimately achieving the purpose of controlling the relative humidity of the room;

[0069] The terminal fresh air valve 9 is controlled specifically to adjust the opening of the terminal fresh air valve 9 according to the deviation between the terminal fresh air volume set value and the actual value, so that the actual fresh air volume is controlled near the set fresh air volume;

[0070] The built-in fan control of the fan coil unit 22 specifically adjusts the terminal circulation air volume according to the deviation between the indoor temperature set value and the actual value, so that the actual indoor temperature is controlled near the set temperature;

[0071] The terminal air reheater 21 is controlled specifically to open the terminal air reheater 21 when the temperature of the room 24 is overcooled, so that the temperature of the room 24 returns to the reheating set temperature;

[0072] The indoor exhaust heat recovery device 13 is controlled specifically as follows: when the outdoor dry-bulb temperature is greater than the indoor return air temperature, the indoor exhaust heat recovery device 13 is turned on to pre-cool the hot and humid outdoor fresh air; when the outdoor dry-bulb temperature is lower than the indoor return air temperature, the indoor exhaust heat recovery device 13 is turned off, and at this time all the outdoor fresh air is bypassed to the fresh air unit 16.

[0073] In the control of the condensing heat recovery regulating valve 8, when the heat transfer temperature difference is taken into account, the actual water inlet temperature can be slightly lower than the indoor air dew point temperature by about 3°C; in the control of the fresh air fan 18, the total fresh air volume not only needs to meet the minimum total fresh air volume requirement, but also needs to meet the dehumidification requirement of the terminal room 24; in the control of the terminal fresh air valve 9, the set value of the terminal fresh air volume is required to be no lower than the minimum fresh air volume of the room.

[0074] In summary, the embodiment of the present invention provides a dual heat recovery type DOAS air conditioner, system and control method, wherein the dual heat recovery link of the system includes condensation heat recovery and indoor exhaust heat recovery. The condensation heat recovery link, that is, when the return water temperature of the fresh air unit is lower than the indoor dew point temperature at the terminal, recovers a part of the condensation heat of the chiller and uses it to heat the return water of the fresh air unit to make it higher than the indoor dew point temperature. The condensation heat recovery avoids the energy consumption of reheating the chilled water at the terminal on the one hand, and reduces the cooling water inlet temperature of the chiller on the other hand, thereby greatly improving the overall energy efficiency of the system. In addition, the chiller The water temperature control method of condensation heat recovery has high control accuracy and can effectively avoid the problem of condensation at the terminal. The indoor exhaust heat recovery link pre-cools the hot and humid outdoor fresh air, thereby reducing the fresh air cooling load and further improving the system energy efficiency. The fresh air unit controls the mixing ratio of fresh air and bypass fresh air through the air valve control, thereby controlling the moisture content of the fresh air supply, and at the same time, supplemented by the adjustment of the fresh air volume, effectively realizes the humidity control of the terminal room by the fresh air unit. The fan coil unit realizes the control of sensible heat exchange by adjusting the size of the circulating air volume, thereby achieving the purpose of accurately controlling the room temperature.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A dual heat recovery DOAS air conditioner, characterized in that: The invention comprises a chiller (1), a condensing heat recovery device (6), a cooling tower (7), an indoor exhaust heat recovery device (13), a fresh air unit (16), an air mixing box (20) and a fan coil unit (22), wherein the water outlet of the chiller (1) is connected to the water inlet of the cooling tower (7) and the fresh air unit (16), the water outlet of the cooling tower (7) and the fresh air unit (16) is connected to the water inlet of the condensing heat recovery device (6), the water outlet of the condensing heat recovery device (6) is connected to the water inlet of the chiller (1) and the fan coil unit (22), and the water outlet of the fan coil unit (22) is connected to the water inlet of the chiller (1). ), the outdoor fresh air (26) is connected to the air inlet of the fresh air unit (16), the air outlet of the fresh air unit (16) is connected to the air inlet of the air mixing box (20), the air outlet of the air mixing box (20) is connected to the air inlet of the room (24), the air outlet of the room (24) is connected to the air inlet of the indoor exhaust heat recovery device (13), the air outlet of the indoor exhaust heat recovery device (13) is connected to the outdoor (25), the air outlet of the room (24) is connected to the air inlet of the fan coil unit (22), and the air outlet of the fan coil unit (22) is connected to the air inlet of the room (24); It includes the control of the chilled water main bypass valve (5), the control of the condensing heat recovery regulating valve (8), the control of the terminal three-way water valve (23), the control of the fresh air fan (18), the control of the exhaust fan (12), the control of the fresh air unit bypass air valve (14) and the fresh air unit air valve (15), the control of the terminal fresh air valve (9), the built-in fan control of the fan coil (22), the control of the terminal air reheater (21) and the control of the indoor exhaust heat recovery device (13); The chilled water main bypass valve (5) is controlled specifically as follows: when the maximum temperature of the terminal room (24) is lower than the indoor set temperature, that is, when the cooling capacity is oversupplied, the chilled water main bypass valve (5) is opened, and the maximum temperature of the terminal room (24) is raised to near the set temperature by adjusting the opening degree; The condensation heat recovery regulating valve (8) is controlled specifically by adjusting the opening of the condensation heat recovery regulating valve (8) according to the deviation between the set value and the actual value of the inlet water temperature of the fan coil unit (22), so that the actual inlet water temperature is controlled above the indoor dew point temperature; The terminal three-way water valve (23) is controlled specifically to adjust the opening of the terminal three-way water valve (23) when the temperature of the room (24) is lower than the indoor set temperature, so that all the chilled water is bypassed back to the chiller (1) to avoid overcooling of the room (24); The control of the fresh air fan (18) and the exhaust fan (12) is specifically to adjust the speed of the fresh air fan (18) according to the deviation between the total fresh air volume set value and the actual value, so that the actual total fresh air volume is controlled near the set total fresh air volume, and the exhaust fan (12) needs to be controlled according to the indoor set pressure to maintain a certain indoor positive pressure; The control of the bypass ventilation valve (14) and the fresh air unit air valve (15) of the fresh air unit is specifically to adjust the opening of the bypass ventilation valve (14) and the fresh air unit air valve (15) according to the deviation between the actual average relative humidity of each room and the set relative humidity, thereby achieving the adjustment of the mixing ratio of the processed fresh air and the bypass fresh air, thereby achieving the control of the moisture content of the fresh air supply, and ultimately achieving the purpose of controlling the relative humidity of the room; The terminal fresh air valve (9) is controlled specifically by adjusting the opening of the terminal fresh air valve (9) according to the deviation between the terminal fresh air volume set value and the actual value, so that the actual fresh air volume is controlled to be close to the set fresh air volume; The built-in fan control of the fan coil unit (22) is specifically to adjust the terminal circulation air volume according to the deviation between the indoor temperature set value and the actual value, so that the actual indoor temperature is controlled near the set temperature; The terminal air reheater (21) is controlled specifically as follows: when the temperature of the room (24) is overcooled, the terminal air reheater (21) is turned on to raise the temperature of the room (24) back to the reheating set temperature; The indoor exhaust heat recovery device (13) is controlled specifically as follows: when the outdoor dry-bulb temperature is greater than the indoor return air temperature, the indoor exhaust heat recovery device (13) is turned on to pre-cool the hot and humid outdoor fresh air; when the outdoor dry-bulb temperature is less than the indoor return air temperature, the indoor exhaust heat recovery device (13) is turned off, and at this time all the outdoor fresh air is bypassed to the fresh air unit (16).

2. A dual heat recovery DOAS air conditioner according to claim 1, characterized in that: A fresh air surface cooler (17) and a fresh air fan (18) are provided at the fresh air unit (16); the water outlet of the chiller (1) is connected to the water inlet of the fresh air surface cooler (17) of the fresh air unit (16); the water outlet of the fresh air surface cooler (17) is connected to the water inlet of the condensing heat recovery device (6); the outdoor fresh air (26) is connected to the air inlet of the fresh air surface cooler (17) of the fresh air unit (16), and is connected to the air inlet of the mixing box (20) through the drive of the fresh air fan (18).

3. A dual heat recovery DOAS air conditioner according to claim 2, characterized in that: It also includes a terminal air reheater (21), and the air discharged from the air outlet of the air mixing box (20) passes through the terminal air reheater (21) and then enters the room (24).

4. A dual heat recovery DOAS air conditioner according to claim 3, characterized in that: It also includes an exhaust fan (12), and the air outlet of the indoor exhaust heat recovery device (13) is connected to the outside (25) through the exhaust fan (12).

5. A dual heat recovery DOAS air conditioner according to claim 4, characterized in that: It also includes a cooling water pump (2) and a chilled water pump (3), the water outlet of the condensing heat recovery device (6) is connected to the water inlet of the chiller (1) through the cooling water pump (2), and the water outlet of the fan coil (22) is connected to the water inlet of the chiller (1) through the chilled water pump (3).

6. A dual heat recovery DOAS air conditioner according to claim 5, characterized in that: It also includes an expansion water tank (4), which is connected to the water inlet of the chilled water pump (3).

7. A dual heat recovery DOAS air conditioner according to claim 6, characterized in that: The system further comprises a temperature sensor (10), a humidity sensor (11), and a flow sensor (19). The temperature sensor (10) is arranged at the room (24), the water inlet and the water outlet of the chiller (1), the water outlet of the condensing heat recovery device (6), the water outlet of the cooling tower (7), the air inlet of the indoor exhaust heat recovery device (13), and the air inlet of the room (24). The humidity sensor (11) is arranged in the room (24). The flow sensor (19) is arranged at the water inlet of the chiller (1), the air outlet of the fresh air fan (18), and the fresh air duct at the end of the room (24).

8. The dual heat recovery DOAS air conditioner according to claim 7, characterized in that: Including chilled water loop, cooling water loop, new exhaust air loop and indoor circulating air loop; The chilled water loop includes a chiller (1), a fresh air surface cooler (17), a condensing heat recovery device (6), a terminal heat exchange device and a chilled water pump (3); The cooling water loop includes a chiller (1), a cooling tower (7), a condensing heat recovery device (6) and a cooling water pump (2); The fresh air exhaust loop includes an indoor exhaust air heat recovery device (13), a fresh air surface cooler (17), a fresh air fan (18), a terminal air reheater (21) and an exhaust air fan (12); The indoor circulating air loop includes a fan coil unit (22) and a terminal air reheater (21).

9. A dual heat recovery DOAS air conditioning control method according to claim 1, characterized in that: In the control of the condensing heat recovery regulating valve (8), when the heat transfer temperature difference is taken into account, the actual water inlet temperature can be slightly lower than the indoor air dew point temperature by about 3°C; in the control of the fresh air fan (18), the total fresh air volume must not only meet the minimum total fresh air volume requirement, but also meet the dehumidification requirement of the terminal room (24); in the control of the terminal fresh air valve (9), the set value of the terminal fresh air volume must not be lower than the minimum fresh air volume of the room.

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