Control method of modularized multi-cold-source cascade energy recovery unit

Abstract

The invention discloses a control method of a modularized multi-cold-source cascade energy recovery unit, and belongs to the technical field of central air conditioner heat recovery automatic control. The modularized multi-cold-source cascade energy recovery unit comprises an exhaust unit, a fresh air unit, a heat recovery unit and an energy recovery device; the temperature and humidity of fresh air are detected according to a fresh air inlet temperature and humidity sensor, one of the following three operation modes is switched: a total heat recovery air conditioning mode, a transition season ventilation mode and a plum rain season dehumidification mode, and the total heat recovery air conditioning mode is started when the temperature is higher than the set temperature; when the temperature is smaller than the set temperature and the humidity is smaller than the set humidity, a transition season ventilation mode is started; when the temperature is lower than the set temperature and the humidity is higher than the set humidity, a plum rain season dehumidification mode is started. The invention provides the method. A proper mode is selected according to the temperature of the fresh air side, energy loss can be reduced, latent heat and sensible heat in exhaust air are fully utilized, and the overall recovery rate is increased.

Description

Technical Field

[0001] The invention relates to a control method for a modular multi-cold source cascade energy recovery unit, belonging to the technical field of central air-conditioning heat recovery automatic control. Background Art

[0002] Currently, heat recovery in central air conditioning and ventilation systems primarily utilizes heat recovery devices using rotary, plate-fin, and heat pipe heat exchange technologies. These products typically offer improvements over traditional devices in terms of recovery efficiency, air isolation, and condensation and water leakage prevention, but they still primarily rely on a single heat recovery circuit or single-stage evaporation structure. In terms of control, most existing units offer only two modes: "full recovery" and "full bypass," failing to implement tiered adjustments based on seasonality and varying outdoor fresh air conditions to achieve energy-saving operational strategies.

[0003] The current single-stage evaporation or sensible heat recovery method fails to fully utilize the latent heat and sensible heat in the exhaust air, resulting in a low overall recovery rate; short circuits are prone to occur in the heat exchange medium or bypass valve structure, leading to air cross-contamination; the temperature at the condensate drain outlet is low, which is prone to condensation and water accumulation, causing leakage or blockage, and cleaning and maintenance are frequent and costly. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: a control method for a modular multi-cold source cascade energy recovery unit, comprising Exhaust fan unit, fresh air unit, heat recovery unit, energy recovery device, The heat recovery unit and the fresh air unit are sequentially arranged on the side of the exhaust unit. The exhaust unit includes an exhaust bypass valve, an exhaust fan, and an exhaust filter. The fresh air unit includes a fresh air bypass valve, a fresh air fan, and a fresh air filter. The heat recovery unit includes a water tank and a wet film heat exchange core. The energy recovery device includes a heat recovery condenser, a pre-cooling surface cooler, a re-cooling evaporator, a reheat condenser, a circulating water pump, a four-way valve, and a compressor. The fresh air unit is provided with a fresh air inlet temperature and humidity sensor, which can detect the temperature and humidity of the fresh air. According to the detection results of the fresh air inlet temperature and humidity sensor, one of the following three operating modes is judged and switched: full heat recovery air-conditioning mode, transition season ventilation mode, and rainy season dehumidification mode. When the fresh air side temperature is greater than the set temperature, the full heat recovery air-conditioning mode is started; when the fresh air side temperature is lower than the set temperature and the humidity is lower than the set humidity, the transition season ventilation mode is started; when the fresh air side temperature is lower than the set temperature and the humidity is higher than the set humidity, the rainy season dehumidification mode is started.

[0005] Preferably, when in full heat recovery air conditioning mode, it includes primary heat recovery and secondary evaporation condensation recovery. The fresh air bypass valve is closed and the fresh air blower is turned on, and the fresh air passes through the fresh air filter, the pre-cooling surface cooler, and the re-cooling evaporator in sequence before entering the use environment; The exhaust bypass valve is closed, and the exhaust fan is turned on, and the exhaust air passes through the exhaust filter, the wet film heat exchange core, the heat recovery condenser, and the exhaust fan and is then discharged outdoors; A heat recovery box is provided between the exhaust fan and the fresh air fan. Start the first-stage heat recovery, the circulating water pump draws cooling water from the bottom of the heat recovery box, pumps it into the fresh air side pre-cooling surface cooler, cools the fresh air, sprays it on the top of the wet film heat exchange core, exchanges heat and moisture with the exhaust air, and then flows back to the bottom of the heat recovery box; The medium water heated by the pre-cooling surface cooler flows from the upper part to the lower part of the wet film heat exchange core in the heat recovery box, and exchanges heat with the exhaust air in the wet film heat exchange core.

[0006] Preferably, a refrigerant is provided inside the compressor. When the fresh air inlet temperature is higher than the set value, the first-stage heat recovery operation is maintained; when the fresh air supply temperature is higher than the set value, the compressor is started and the four-way valve is kept off to enter the second-stage evaporation and condensation recovery; In the secondary evaporation condensation recovery: The compressor compresses the refrigerant into a high-temperature and high-pressure gas, which is then converted into a medium-temperature and high-pressure liquid after heat exchange with exhaust air in the heat recovery condenser. The refrigerant is throttled by the throttling mechanism, converted into a low-temperature, low-pressure liquid, and then enters the re-cooling evaporator, exchanges heat with the pre-cooled fresh air, and is inhaled into the compressor after being vaporized. In this process, the temperature and humidity of the fresh air can be reduced.

[0007] Preferably, in transitional season ventilation mode, Open the fresh air bypass valve and start the fresh air blower, and the fresh air passes through the fresh air filter and is directly output to the air supply side; Open the exhaust bypass valve and start the exhaust fan, and the exhaust air is directly output to the exhaust side through the exhaust filter; The fresh air fan and the exhaust air fan include variable frequency fans, and the fresh air fan and the exhaust air fan can be adjusted to operate at an energy-saving frequency.

[0008] Preferably, in the rainy season dehumidification mode: Close the fresh air bypass valve and turn on the fresh air blower, so that the fresh air passes through the fresh air filter, the pre-cooling surface cooler, the re-cooling evaporator, and the reheating condenser in sequence and is output to the air supply side; Open the exhaust bypass valve and start the fresh air blower, and the exhaust air passes through the exhaust filter and is directly output to the exhaust side; The four-way valve and the compressor are started, and the refrigerant completes the heat exchange cycle in the reheat condenser and the recooling evaporator in turn to achieve cooling, dehumidification and reheating of the fresh air.

[0009] Preferably, the fresh air fan and the exhaust fan are controlled by variable frequency motors. In full heat recovery air conditioning mode, the fresh air fan and the exhaust fan operate at rated power. In rainy season dehumidification mode, the fresh air fan operates at rated power, and the exhaust fan operates at an energy-saving frequency. In transitional season ventilation mode, the fresh air fan and the exhaust fan operate at an energy-saving frequency.

[0010] Preferably, the fresh air fan and the exhaust fan are both provided with a detection module, which can detect whether the fresh air fan and the exhaust fan are rotating normally and whether the current is overloaded. When an abnormality is detected, a fault alarm is issued and the machine is shut down for protection.

[0011] Preferably, the fault detection of the bypass valve, water pump and compressor includes: the actuator feedback position signal of the fresh air bypass valve and the exhaust bypass valve, if it does not reach the position within the specified time, a fault is issued; the water flow switch and current overcurrent detection of the first-level heat recovery circulating water pump; the high-pressure, low-pressure, high-temperature protection switch and current overcurrent detection of the second-level heat recovery compressor.

[0012] Preferably, a control device is provided on the side of the fresh air unit, and the control device includes a processor. The processor can receive signals and control various devices according to the signals.

[0013] An air conditioner, preferably, adopts the control method of a modular multi-cold source cascade energy recovery unit during the operation of the air conditioner.

[0014] The beneficial effects of the present invention are: The present invention incorporates a fresh air temperature and humidity sensor, and based on the signal detected by the sensor, determines one of the following modes: full heat recovery air conditioning mode, transitional season ventilation mode, or rainy season dehumidification mode. Selecting the appropriate mode based on the fresh air side temperature reduces energy loss, fully utilizes the latent and sensible heat in the exhaust air, and improves overall recovery rates.

[0015] Through the present invention, the exhaust bypass valve and the fresh air bypass valve are closed in the full heat recovery air-conditioning mode, so that the fresh air and the exhaust air always pass through the recovery box and the heat exchanger, avoiding the crossover of the fresh air and the exhaust air and ensuring air isolation. In the transition season ventilation mode, the exhaust bypass valve and the fresh air bypass valve are opened, and the exhaust fan and the fresh air fan are turned on to directly introduce the fresh air into the room and exhaust the air directly to the outside without activating the recovery device, thereby significantly reducing energy consumption. In the dehumidification mode in the rainy season, the state of the exhaust bypass valve is automatically switched according to the temperature and humidity feedback, accurately realizing the dehumidification and reheating functions, and improving energy saving efficiency.

[0016] The present invention installs a wet film heat exchange core between the water tank at the bottom of the heat recovery housing and the heat recovery condenser. The water inside the water tank can be pumped into the pre-cooling condenser of the fresh air housing. During this process, the water heats up in the pre-cooling condenser and is then sprayed on the top of the wet film heat exchange core to exchange heat with the exhaust air. This enables open circulation, reducing the number of external water replenishments. After the pre-cooling condenser absorbs the heat of the fresh air, the water temperature rises, and then sprays on the top of the wet film to absorb the heat in the exhaust air, making fuller use of the energy in the primary recovery process. The circulating water pump uses a water flow switch and current detection to ensure that the circulating water path is unobstructed, preventing the water pump from idling and clogging, and improving system reliability.

[0017] Through the present invention, a two-stage evaporation and condensation heat recovery mode is provided. When the fresh air supply temperature is still higher than the set value after the first-stage heat recovery, the four-way valve remains in the power-off state, and the compressor sucks in and compresses the low-pressure side refrigerant, sends it to the heat recovery condenser, and exchanges heat with the exhaust air; the liquid refrigerant is throttled to the re-cooling evaporator, and exchanges heat with the pre-cooled fresh air; in the dehumidification mode during the rainy season, the four-way valve is powered on, and the high-pressure refrigerant is directed to the reheat condenser to reheat the dehumidified fresh air. The refrigerant cooled by the reheat condenser is first throttled by the throttling mechanism, and then enters the re-cooling evaporator to dehumidify the fresh air.

[0018] Through the present invention, the fresh air fan and the exhaust fan adopt variable frequency fans, which operate at different frequencies according to different modes to achieve energy saving. A processor is set in the control cabinet, which can process the signals detected by various sensors to ensure the automatic operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the operating structure of the full heat recovery air conditioning mode of the present invention.

[0020] Figure 2 This is a schematic diagram of the initial mode operation structure of the plum rain season of the present invention.

[0021] Figure 3 This is a schematic diagram of the operating structure of the transitional season ventilation mode of the present invention.

[0022] Figure 4 This is a schematic diagram of the operating principle of the refrigeration system of the present invention.

[0023] Figure 5 Flowchart of the control method of the present invention.

[0024] In the figure: 11-exhaust box, 12-exhaust filter, 13-exhaust bypass valve, 14-exhaust fan, 21-heat recovery box, 22-wet film heat exchange core, 23-water tank, 31-fresh air box, 32-fresh air filter, 33-pre-cooling surface cooler, 34-circulating water pump, 35-fresh air fan, 36-fresh air bypass valve, 37-water flow switch, 41-compressor, 42-four-way valve, 43-heat recovery condenser, 44-recooling evaporator, 45-reheat condenser, 46-throttling mechanism, 51-exhaust temperature and humidity sensor, 52-fresh air supply temperature and humidity sensor, 53-lack of air pressure differential switch, 54-low pressure switch, 55-high temperature switch, 56-high pressure switch, 57-control cabinet, 58-fresh air inlet temperature and humidity sensor. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments. Example 1

[0026] like Figure 1-Figure 5 As shown, a control method for a modular multi-cold source cascade energy recovery unit.

[0027] In this embodiment, an air conditioner is provided, including an exhaust fan unit, a fresh air fan unit, a heat recovery unit, an energy recovery device, and a control method of a modular multi-cold source cascade energy recovery unit as described below.

[0028] The exhaust unit is flanked by a heat recovery unit and a fresh air unit. The exhaust unit includes an exhaust bypass valve 13, an exhaust fan 14, and an exhaust filter 12; the fresh air unit includes a fresh air bypass valve 36, a fresh air fan 35, and a fresh air filter 32; the heat recovery unit includes a water tank 23 and a wet film heat exchange core 22; and the energy recovery device includes a heat recovery condenser 43, a pre-cooling condenser 33, a re-cooling evaporator 44, a reheat condenser 45, a circulating water pump 34, a four-way valve 42, and a compressor 41.

[0029] Reference Figure 1 , The exhaust unit is disposed within the exhaust housing 11, the fresh air unit is disposed within the fresh air housing 31, and a heat recovery housing 21 is disposed between the exhaust housing 11 and the fresh air housing 31. The exhaust housing 11 is generally rectangular, with an exhaust air inlet disposed on the side of the lower end and an exhaust air outlet disposed on the top. Exhaust air can enter the exhaust housing 11 through the exhaust air inlet and be guided out of the exhaust housing 11 by the exhaust fan 14. While within the exhaust housing 11, the exhaust air can flow into the heat recovery housing 21 or not.

[0030] The heat recovery housing 21 is equipped with a water tank 23 at the bottom, a wet-film heat exchange core 22 in the middle, and a heat recovery condenser 43 at the top, positioned at an angle. Exhaust air flowing into the heat recovery housing 21 passes through the wet-film heat exchange core 22 and the heat recovery condenser 43 before reentering the exhaust housing 11. The tilted heat recovery condenser 43 increases the contact surface between the exhaust air and the heat recovery condenser 43.

[0031] The fresh air unit is arranged inside the fresh air box 31. A control device is also arranged inside the fresh air box 31. The control device includes a control cabinet 57. A processor is arranged in the control cabinet. The processor can receive signals and control various devices according to the signals.

[0032] In this embodiment, an exhaust bypass valve 13 is located in the middle of the exhaust housing 11. An exhaust fan 14 is located on top of the exhaust bypass valve 13. A low-pressure differential pressure switch 53 is located on top of the exhaust fan 14. An exhaust filter 12 is located on the side bottom of the exhaust housing 11, and an exhaust temperature and humidity sensor 51 is located on the exhaust filter 12. A compressor 41, a low-pressure switch 54, a high-temperature switch 55, a high-pressure switch 56, and a four-way valve 42 are located on the inner bottom of the exhaust housing 11, sequentially from left to right. Pipelines at the bottom of the exhaust housing 11 extend to the bottom of the fresh air housing 31. A circulating water pump 34, a water flow switch 37, a throttling mechanism 46, a reheat condenser 45, a recooling evaporator 44, and a precooling surface cooler 33 are located on the inner bottom of the fresh air housing 31, sequentially from left to right.

[0033] A heat recovery housing 21 is located between the exhaust housing 11 and the fresh air housing 31. A water tank 23 is located at the bottom of the heat recovery housing 21, a wet film heat exchange core 22 is located in the middle, and a heat recovery condenser 43 is located at an angle at the top. A fresh air bypass valve 36 is located in the middle of the fresh air housing 31, and a fresh air blower 35 and a control cabinet 57 are located at the top. The control cabinet 57 is located outside the housing. A low-pressure differential switch 53 is located at the top of the fresh air blower 35, and a fresh air supply temperature and humidity sensor 52 is located at the fresh air blower 35. A fresh air filter 32 is located at the bottom side of the fresh air housing 31, and a sensor 58 is located at the top of the fresh air filter 32. The control cabinet 57 houses a processor that receives data detected by various sensors and controls various devices based on the data.

[0034] In this embodiment, the exhaust bypass valve 13 and the fresh air bypass valve 36 can be opened or closed, and controlling the states of the exhaust bypass valve 13 and the fresh air bypass valve 36 can control the flow direction of the exhaust air and the fresh air.

[0035] When the exhaust bypass valve 13 is closed, the exhaust air enters the bottom of the exhaust box 11 from the exhaust filter 12, passes through the heat recovery box 21, enters the top of the exhaust box 11 from the top of the heat recovery box 21, and is discharged from the exhaust box 11 through the exhaust fan 14.

[0036] When the exhaust bypass valve 13 is opened, exhaust air enters the bottom of the exhaust box 11 from the exhaust filter 12 , directly passes through the exhaust bypass valve 13 , and is discharged from the exhaust box 11 through the exhaust fan 14 .

[0037] When the fresh air bypass valve 36 is closed, the fresh air enters the bottom of the fresh air box 31 from the fresh air filter 32, passes through the pre-cooling surface cooler 33, the re-cooling evaporator 44, the reheating condenser 45, and the throttling mechanism 46 arranged at the bottom of the fresh air box 31 in sequence, and then goes upward and is discharged from the fresh air box 31 through the fresh air fan 35.

[0038] When the fresh air bypass valve 36 is opened, fresh air enters the bottom of the fresh air box 31 from the fresh air filter 32, directly enters the top of the fresh air box 31 through the fresh air bypass valve 36, and is discharged from the fresh air box 31 through the fresh air blower 35.

[0039] In this embodiment, the operation modes include a full heat recovery air conditioning mode, a transition season ventilation mode, and a rainy season dehumidification mode.

[0040] During use, the fresh air supply temperature and humidity sensor 52 can detect the temperature and humidity of the fresh air entering the fresh air box 31 and transmit the detected data to the control cabinet 57. The control cabinet 57 can set the use demand of the fresh air supply temperature during use. When the detected fresh air side temperature is greater than the use temperature setting, the full heat recovery air conditioning mode is activated; when the detected fresh air side temperature is less than the use temperature setting, the transition season ventilation mode is activated; when the detected fresh air side temperature is less than the use temperature setting, but the humidity is greater than the set humidity, the dehumidification mode is activated.

[0041] In full heat recovery air conditioning mode, the fresh air bypass valve 36 is closed and the fresh air fan 35 is turned on. Fresh air enters the bottom of the fresh air box 31 through the fresh air filter 32, passes through the pre-cooling surface cooler 33, and then moves upward through the fresh air fan 35. It is then discharged from the fresh air box 31 and sent to the operating environment. At the same time, the exhaust bypass valve 13 in the exhaust box 11 is closed and the exhaust fan 14 is turned on.

[0042] The full heat recovery air conditioning mode includes the primary heat recovery mode and the secondary evaporation and condensation heat recovery mode. The primary heat recovery mode is executed first. If the treated fresh air temperature cannot reach the set state, the secondary evaporation and condensation heat recovery mode is activated.

[0043] In the primary heat recovery mode, the circulating water pump 34 is turned on, exhaust air enters the exhaust housing 11 through the exhaust filter 12, and enters the heat recovery housing 21 from the bottom of the exhaust housing. The exhaust air passes through the wet film heat exchange core 22, then upwards, passes through the heat recovery condenser 43, and enters the exhaust fan 14, and is discharged outdoors through the exhaust fan 14. The circulating water pump 34 extracts condensed water from the bottom water tank 23 of the heat recovery housing 21 and pumps it into the pre-cooling surface cooler 33 in the fresh air housing 31 to pre-cool the fresh air. The heated medium water is sprayed on the top of the wet film heat exchange core 22 in the middle of the heat recovery housing 21, and fully exchanges heat and moisture with the exhaust air in the wet film heat exchange core 22. After cooling, the medium water is poured into the water tank at the bottom of the heat recovery housing and enters the water pump again. An open cycle is formed to achieve energy recovery, and the exhaust air flows to the exhaust fan 11 after sufficient heat and moisture exchange in the wet film heat exchange core 22 and the humidity tends to be saturated.

[0044] In this embodiment, the frequency of the circulating water pump 34 can be adjusted according to the detected fresh air supply temperature. The data detected by the fresh air supply temperature and humidity sensor 52 is transmitted to the processor in the control cabinet 57, and the processor is set with a set temperature.

[0045] The circulating water pump 34 can adjust its frequency based on the fresh air supply temperature and the set temperature difference. In this embodiment, the adjustment range is: 25-50Hz, temperature difference Δt = fresh air supply temperature - set temperature, and the adjustment period f is 10-60s. In this embodiment, the adjustment period f is 30s. The amplitude a (Hz) of the adjustment frequency is shown in the following table:

[0046] After the circulating water pump is turned on, it runs at a full-load frequency of 50Hz, and then the frequency of the circulating water pump is adjusted by detecting the temperature difference. When the temperature difference Δt>0.5℃, the water pump runs at a full-load frequency of 50Hz; when the temperature difference is -0.5<Δt≦0.5℃, the circulating water pump frequency is not adjusted and maintains the existing frequency; when the temperature difference is -0.5≦Δt<-1℃, the circulating water pump frequency is reduced by 1Hz every adjustment cycle (30s); when the temperature difference is -1≦Δt<-1.5℃, the circulating water pump frequency is reduced by 3Hz every adjustment cycle (30s); as in the above table, when the circulating water pump frequency drops to 25Hz, the temperature difference Δt<-0.5℃, then the 25Hz frequency is maintained and no further adjustment is made.

[0047] When the fresh air processing temperature cannot reach the set state after the first-level heat recovery is running, the second-level evaporation and condensation heat recovery system is turned on. At this time, the four-way valve 42 is not powered on and the compressor 41 is started. A refrigerant is provided inside the compressor 41. The compressor 41 can compress the refrigerant into a high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant enters the heat recovery condenser 43 and exchanges heat with the exhaust air after the heat and moisture exchange, becoming a medium-temperature and high-pressure liquid refrigerant. The medium-temperature and high-pressure liquid refrigerant is converted into a low-temperature and low-pressure liquid refrigerant through the throttling mechanism 46 and then flows into the re-cooling evaporator 44 to exchange heat with the pre-cooled fresh air. In the process of heat exchange, the low-temperature and low-pressure gaseous refrigerant is sucked into the compressor. The fresh air is cooled and dehumidified in this process and then enters the fresh air blower.

[0048] In this embodiment, compressor 41 is a variable frequency compressor capable of tiered output power. Compressor 41 adjusts its operating frequency based on the detected fresh air supply temperature. Fresh air supply temperature sensor 41 detects the fresh air outlet temperature and compares it with a set temperature to calculate the temperature difference Δt.

[0049] When the temperature difference is 0.5℃<Δt≦1℃, the compressor 41 is started and the power of the compressor 41 is loaded to 50%; when the temperature difference Δt>1℃, the power of the compressor 41 is loaded to 100%; when the temperature difference is -2℃<Δt≦-1℃, the output of the compressor 41 is reduced by 50%; when the temperature difference Δt≦-2℃, the compressor 41 is turned off.

[0050] In this embodiment, the above judgment is performed every 3 minutes of operation to avoid frequent switching caused by short-term temperature fluctuations. The output power of compressor 41 is 0, 50%, and 100%. Compressor 41 can achieve graded output according to the real-time temperature difference. When the fresh air is close to the set temperature, only 50% of the power of compressor 41 is used to maintain the cooling capacity to avoid overcooling; when the temperature difference is large, the temperature is quickly lowered at full capacity. The operating conditions of compressor 41 are adjusted after a 3-minute delay to avoid frequent start-stop caused by short-term small fluctuations and to increase the life of the equipment.

[0051] In the transitional season ventilation mode, the fresh air bypass valve 36 is opened, and the fresh air fan 35 is turned on in the fresh air box 31. The fresh air passes through the fresh air filter 32 and the fresh air bypass valve 36, then enters the fresh air fan 35 and is then sent into the use environment through the fresh air fan 35. On the exhaust side, the exhaust bypass valve 13 is opened, and the exhaust fan 14 is turned on. The exhaust air enters the exhaust box 11 through the exhaust filter 12, enters the exhaust fan 14 through the exhaust bypass valve 13, and is discharged outdoors through the exhaust fan 14.

[0052] In the rainy season dehumidification mode, the fresh air bypass valve 36 is closed and the fresh air fan 35 is turned on in the fresh air box 31. The fresh air passes through the fresh air filter 32, the pre-cooling surface cooler 33, the re-cooling evaporator 44, and the reheating condenser 45, then enters the fresh air fan 35 and is then sent into the operating environment by the fresh air fan 35. On the exhaust side, the exhaust bypass valve 13 is opened, and the exhaust fan 14 is turned on. The exhaust air passes through the exhaust filter 12 and enters the exhaust box 11. After flowing through the exhaust bypass valve 13, it enters the exhaust fan 14 and is sent outdoors by the exhaust fan 14. At the same time, the four-way valve 42 is energized, starting the compressor 41. The compressor 41 compresses the low-temperature and low-pressure gaseous refrigerant into high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant passes through the four-way valve 42 and enters the reheat condenser 45 to exchange heat with the fresh air after passing through the recooling evaporator 44, becoming medium-temperature and high-pressure liquid refrigerant. The medium-temperature and high-pressure liquid refrigerant passes through the throttling mechanism 46 and becomes low-temperature and low-pressure liquid refrigerant and then enters the recooling evaporator 44. The low-temperature and low-pressure liquid refrigerant passes through the recooling evaporator 44 and exchanges heat with the fresh air that passes through the pre-cooling surface cooler 33 to become low-temperature and low-pressure gaseous refrigerant. Then, the low-temperature and low-pressure gaseous refrigerant is sucked in by the compressor 41, and the fresh air is further cooled and dehumidified, and then heated through the reheat condenser 45. After the fresh air is converted to a medium-temperature and low-humidity state, it enters the fresh air fan 35 and is sent into the use environment by the fresh air fan.

[0053] In this embodiment, the fresh air fan 35 and the exhaust fan 14 include variable frequency fans. The fresh air fan 35 operates at rated power in the full heat recovery air conditioning mode and the rainy season dehumidification mode, and operates at energy-saving frequency in the transition season ventilation mode.

[0054] In this embodiment, the energy-saving frequency is when the fresh air side ventilation valve and the exhaust air side ventilation valve are opened, the air volume increases, and a constant air volume is ensured by adjusting the fan frequency.

[0055] The ways to adjust the fan frequency are: 1. Set a fixed frequency as the energy-saving frequency; 2. Control the fan frequency based on the wind pressure difference, that is, determine the fan operating frequency based on the pressure difference before and after the fan in the full heat recovery air conditioning mode; 3. Control the fan frequency according to the controlled air volume, that is, the air flow rate is detected by the wind speed sensor in the air duct, and then the flow rate is calculated as the measured air volume. The controller adjusts the fan frequency to make the measured air volume consistent with the set air volume.

[0056] The exhaust fan 14 operates at rated power in the full heat air conditioning mode, and operates at energy-saving frequency in the transition season ventilation mode and the rainy season dehumidification mode.

[0057] Air-deficit pressure differential switches 53 are installed on the outlet side of the exhaust fan 14 and the fresh air fan 35. These switches detect whether the fans are operating normally. The pressure differential switches 53 transmit this data to a processor within a control cabinet 57, which processes the signals from both switches 53. When a pressure differential signal is present, the fans are operating normally; when no pressure differential signal is present, a fault is detected, and an alarm is issued. The operating current of the fresh air fan 35 and the exhaust fan 14 is also monitored. If the operating current exceeds the rated value, the processor issues an alarm and provides fault feedback.

[0058] The fresh air bypass valve 36 and the exhaust air bypass valve 13 are provided with air valve actuators, and the fresh air bypass valve 36 and the exhaust air bypass valve 13 provide signal feedback of the open position and the closed position through the air valve actuator. When the processor gives the valve opening or closing instruction, if the feedback signal of the open position or the closed position is not received within the running time, the processor will issue an alarm prompt.

[0059] In the primary heat recovery mode, the circulating water pump 34 determines the working status of the water pump through the water flow switch set on the water outlet side of the water pump, and can detect its own operating current overcurrent detection. When the operating current is higher than the rated value, the signal is transmitted to the processor, and the processor issues an alarm prompt.

[0060] In the secondary heat recovery mode, the compressor is protected and controlled by the system's high-pressure, low-pressure, and high-temperature switches. At the same time, the compressor has an operating current overcurrent detection. When the operating current is higher than the rated value, the signal is transmitted to the processor, and the processor issues an alarm.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments and that various modifications and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such modifications and improvements are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A control method for a modular multi-cold source cascade energy recovery unit, comprising: Exhaust fan unit, fresh air unit, heat recovery unit, energy recovery device, The heat recovery unit and the fresh air unit are sequentially arranged on the side of the exhaust unit. The exhaust unit includes an exhaust bypass valve, an exhaust fan, and an exhaust filter. The fresh air unit includes a fresh air bypass valve, a fresh air fan, and a fresh air filter. The heat recovery unit includes a water tank and a wet film heat exchange core. The energy recovery device includes a heat recovery condenser, a pre-cooling surface cooler, a re-cooling evaporator, a reheat condenser, a circulating water pump, a four-way valve, and a compressor. Its characteristics are: The fresh air unit is provided with a fresh air inlet temperature and humidity sensor, which can detect the temperature and humidity of the fresh air. According to the detection results of the fresh air inlet temperature and humidity sensor, one of the following three operating modes is judged and switched: full heat recovery air-conditioning mode, transition season ventilation mode, and rainy season dehumidification mode. When the fresh air side temperature is greater than the set temperature, the full heat recovery air-conditioning mode is started; when the fresh air side temperature is lower than the set temperature and the humidity is lower than the set humidity, the transition season ventilation mode is started; when the fresh air side temperature is lower than the set temperature and the humidity is higher than the set humidity, the rainy season dehumidification mode is started.

2. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: When in full heat recovery air conditioning mode, it includes primary heat recovery and secondary evaporation condensation recovery. The fresh air bypass valve is closed and the fresh air blower is turned on, and the fresh air passes through the fresh air filter, the pre-cooling surface cooler, and the re-cooling evaporator in sequence before entering the use environment; The exhaust bypass valve is closed, and the exhaust fan is turned on, and the exhaust air passes through the exhaust filter, the wet film heat exchange core, the heat recovery condenser, and the exhaust fan and is then discharged outdoors; A heat recovery box is provided between the exhaust fan and the fresh air fan. When the fresh air inlet temperature is higher than the set temperature, Start the first-stage heat recovery, the circulating water pump draws cooling water from the bottom of the heat recovery box, pumps it into the fresh air side pre-cooling surface cooler, cools the fresh air, sprays it on the top of the wet film heat exchange core, exchanges heat and moisture with the exhaust air, and then flows back to the bottom of the heat recovery box; The medium water heated by the pre-cooling surface cooler flows from the upper part to the lower part of the wet film heat exchange core in the heat recovery box, and exchanges heat with the exhaust air in the wet film heat exchange core.

3. The control method of a modular multi-cold source cascade energy recovery unit according to claim 2, characterized in that: The compressor is provided with a refrigerant inside. When the fresh air inlet temperature is higher than the set value, the first-stage heat recovery operation is maintained; when the fresh air supply temperature is higher than the set value, the compressor is started and the four-way valve is kept off to enter the second-stage evaporation and condensation recovery; In the secondary evaporation condensation recovery: The compressor compresses the refrigerant into a high-temperature and high-pressure gas, which is then converted into a medium-temperature and high-pressure liquid after heat exchange with exhaust air in the heat recovery condenser. The refrigerant is throttled by the throttling mechanism, converted into a low-temperature, low-pressure liquid, and then enters the re-cooling evaporator, exchanges heat with the pre-cooled fresh air, and is inhaled into the compressor after being vaporized. In this process, the temperature and humidity of the fresh air can be reduced.

4. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: In transitional season ventilation mode, Open the fresh air bypass valve and start the fresh air blower, and the fresh air passes through the fresh air filter and is directly output to the air supply side; Open the exhaust bypass valve and start the exhaust fan, and the exhaust air is directly output to the exhaust side through the exhaust filter; The fresh air fan and the exhaust air fan include variable frequency fans, and the fresh air fan and the exhaust air fan can be adjusted to operate at an energy-saving frequency.

5. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: In the rainy season dehumidification mode: Close the fresh air bypass valve and turn on the fresh air blower, so that the fresh air passes through the fresh air filter, the pre-cooling surface cooler, the re-cooling evaporator, and the reheating condenser in sequence and is output to the air supply side; Open the exhaust bypass valve and start the fresh air blower, and the exhaust air passes through the exhaust filter and is directly output to the exhaust side; The four-way valve and the compressor are started, and the refrigerant completes the heat exchange cycle in the reheat condenser and the recooling evaporator in turn to achieve cooling, dehumidification and reheating of the fresh air.

6. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: The fresh air fan and the exhaust fan are controlled by variable frequency motors. In full heat recovery air conditioning mode, the fresh air fan and the exhaust fan operate at rated power. In rainy season dehumidification mode, the fresh air fan operates at rated power, and the exhaust fan operates at an energy-saving frequency. In transitional season ventilation mode, the fresh air fan and the exhaust fan operate at an energy-saving frequency.

7. The control method of a modular multi-cold source cascade energy recovery unit according to claim 6, characterized in that: The fresh air fan and the exhaust air fan are both provided with a detection module, which can detect whether the fresh air fan and the exhaust air fan are rotating normally and whether the current is overloaded. When an abnormality is detected, a fault alarm is issued and the machine is shut down for protection.

8. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: Fault detection of bypass valves, water pumps and compressors includes: feedback position signals from the actuators of the fresh air bypass valve and the exhaust air bypass valve. If the position is not reached within the specified time, a fault is generated; water flow switch and current overcurrent detection of the first-stage heat recovery circulating water pump; high-pressure, low-pressure, high-temperature protection switches and current overcurrent detection of the second-stage heat recovery compressor.

9. The control method of a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: A control device is provided on the side of the fresh air unit. The control device includes a processor. The processor can receive signals and control various devices according to the signals.

10. An air conditioner, characterized in that: During the operation of the air conditioner, a control method for a modular multi-cold source cascade energy recovery unit according to any one of claims 1 to 9 is adopted.

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