A control method of a modular multi-cold-source cascade energy recovery unit

Abstract

The application discloses a control method of a modular multi-cold-source cascade energy recovery unit, and belongs to the technical field of automatic control of central air-conditioning heat recovery, which comprises an exhaust fan unit, a fresh air fan unit, a heat recovery unit and an energy recovery device, the fresh air fan unit is provided with a fresh air inlet temperature and humidity sensor, the temperature and humidity of fresh air are detected according to the fresh air inlet temperature and humidity sensor, and one of the following three operation modes is switched: a full-heat recovery air-conditioning mode, a transition season ventilation mode and a plum rain season dehumidification mode; when the temperature is greater than a set temperature, the full-heat recovery air-conditioning mode is started; when the temperature is less than the set temperature and the humidity is less than a set humidity, the transition season ventilation mode is started; and when the temperature is less than the set temperature and the humidity is greater than the set humidity, the plum rain season dehumidification mode is started. According to the temperature of the fresh air side, the application can select a suitable mode, reduce energy loss, fully utilize latent heat and sensible heat in exhaust air and improve overall recovery rate.

Description

TECHNICAL FIELD

[0001] The application relates to a control method of a modular multi-cold-source cascade energy recovery unit, and belongs to the technical field of automatic control of central air conditioning heat recovery. BACKGROUND

[0002] At present, heat recovery of a central air conditioning ventilation system mainly adopts a rotary wheel type, a plate-fin type, a heat pipe type and the like to recover heat exchange technology. These products are usually improved in recovery efficiency, air isolation, anti-condensation and water leakage and the like compared with traditional devices, but still mainly adopt a single heat recovery loop or a single-stage evaporation structure. In the control part, most of the existing units are only provided with two modes of 'full recovery' and 'full bypass', and cannot be adjusted in stages according to different seasons and different outdoor fresh air states to realize an energy-saving operation strategy.

[0003] In the current single-stage evaporation or sensible heat recovery mode, the latent heat and the sensible heat in the exhaust air cannot be fully utilized, the overall recovery rate is low, short circuit is prone to occur in the heat exchange medium or the bypass valve structure, air cross contamination is caused, condensate water is prone to occur at the position of the condensate water drainage port, and leakage or blockage is caused, cleaning and maintenance are frequent and the cost is high. SUMMARY

[0004] The technical problem to be solved by the application is to provide a control method of a modular multi-cold-source cascade energy recovery unit.

[0005] The exhaust air unit, the fresh air unit, the heat recovery unit and the energy recovery device,

[0006] The exhaust air unit, the fresh air unit, the heat recovery unit and the energy recovery device,

[0007] The fresh air unit is provided with a fresh air inlet temperature and humidity sensor, and the fresh air inlet temperature and humidity sensor can detect the temperature and humidity of fresh air,

[0008] According to the detection result of the fresh air inlet temperature and humidity sensor, one of the following three operation modes is judged and switched: a full heat recovery air conditioning mode, a transition season ventilation mode and a plum rain season dehumidification mode. When the temperature of fresh air is greater than a set temperature, the full heat recovery air conditioning mode is started. When the temperature of fresh air is less than the set temperature and the humidity is less than a set humidity, the transition season ventilation mode is started. When the temperature of fresh air is less than the set temperature and the humidity is greater than the set humidity, the plum rain season dehumidification mode is started.

[0009] Preferably, in the full heat recovery air conditioning mode, one-stage heat recovery, two-stage evaporation condensation recovery,

[0010] Close the fresh air bypass valve, open the fresh air fan, and the fresh air passes through the fresh air filter, the pre-cooling surface cooler, and the re-cooling evaporator in turn before entering the use environment;

[0011] Close the exhaust air bypass valve, open the exhaust air fan, and the exhaust air passes through the exhaust air filter, the wet membrane heat exchange core, the heat recovery condenser, and the exhaust fan before being discharged outside;

[0012] A heat recovery tank is provided between the exhaust air fan and the fresh air fan,

[0013] Start one-stage heat recovery, the circulating water pump extracts cooling water from the bottom of the heat recovery tank, pumps it into the fresh air side pre-cooling surface cooler to cool the fresh air, and sprays it at the top of the wet membrane heat exchange core to exchange heat with the exhaust air before returning to the bottom of the heat recovery tank;

[0014] The medium water warmed by the pre-cooling surface cooler exchanges heat with the exhaust air above and below the wet membrane heat exchange core in the heat recovery tank.

[0015] Preferably, the compressor is internally provided with refrigerant, and when the fresh air inlet temperature is higher than the set value, one-stage heat recovery is maintained; when the fresh air outlet temperature is higher than the set value, the compressor is started and the four-way valve is powered off to enter two-stage evaporation condensation recovery;

[0016] In two-stage evaporation condensation recovery,

[0017] The compressor compresses the refrigerant into high-temperature and high-pressure gas, which is converted into medium-temperature and high-pressure liquid after exchanging heat with the exhaust air through the heat recovery condenser,

[0018] The refrigerant is throttled by the throttling mechanism, converted into low-temperature and low-pressure liquid, and then enters the re-cooling evaporator to exchange heat with the pre-cooled fresh air, vaporized and sucked into the compressor, which can reduce the temperature and humidity of the fresh air.

[0019] Preferably, in the transition season ventilation mode,

[0020] Open the fresh air bypass valve and open the fresh air fan, and the fresh air passes through the fresh air filter and is directly output to the supply air side;

[0021] Open the exhaust air bypass valve and open the exhaust air fan, and the exhaust air passes through the exhaust air filter and is directly output to the exhaust air side;

[0022] 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 run at energy-saving frequency.

[0023] Preferably, in the Meiyu season dehumidification mode:

[0024] Close the fresh air bypass damper and open the fresh air fan, and the fresh air sequentially passes through the fresh air filter, the pre-cooling cooling coil, the re-cooling evaporator, and the re-heating condenser and is output to the supply air side;

[0025] Open the exhaust air bypass damper and open the fresh air fan, and the exhaust air passes through the exhaust air filter and is directly output to the exhaust air side;

[0026] Start the four-way valve and the compressor, and the refrigerant sequentially completes heat exchange circulation in the re-heating condenser and the re-cooling evaporator to realize cooling and dehumidification and reheating of the fresh air.

[0027] Preferably, the fresh air fan and the exhaust air fan adopt variable frequency motor control; in the total heat recovery air conditioning mode, the fresh air fan and the exhaust air fan operate at rated power; in the Meiyu season dehumidification mode, the fresh air fan operates at rated power and the exhaust air fan operates at energy-saving frequency; in the transition season ventilation mode, the fresh air fan and the exhaust air fan operate at energy-saving frequency.

[0028] Preferably, the fresh air fan and the exhaust air fan are each provided with a detection module, the detection module can detect whether the fresh air fan and the exhaust air fan rotate normally and whether the current is overloaded, and when an abnormality is detected, a fault alarm is issued and the machine is stopped for protection.

[0029] Preferably, the fault detection of the bypass valve, the water pump and the compressor includes: feedback position signals of the actuators of the fresh air bypass damper and the exhaust air bypass damper, if the positions are not reached within a specified time, a fault is issued; water flow switch and current overload detection of the primary heat recovery circulating water pump; high pressure, low pressure, high temperature protection switch and current overload detection of the secondary heat recovery compressor.

[0030] Preferably, the fresh air unit is provided with a control device on the side, and the control device includes a processor which can receive signals and control various devices according to the signals.

[0031] An air conditioner, preferably, the air conditioner adopts the control method of the modular multi-cold-source cascade energy recovery unit during operation.

[0032] The beneficial effects of the present application are:

[0033] Through the application, the fresh air temperature and humidity sensor is provided, and one of the following modes is determined according to the signal detected by the fresh air temperature and humidity sensor: running the full heat recovery air conditioner mode, the ventilation mode in the transition season, and the dehumidification mode in the plum rain season. The appropriate mode is selected according to the temperature of the fresh air side, so that the energy loss is reduced, the latent heat and sensible heat in the exhaust air are fully utilized, and the overall recovery rate is improved.

[0034] Through the application, in the full heat recovery air conditioner mode, the exhaust air bypass valve and the fresh air bypass valve are closed, so that the fresh air and the exhaust air always pass through the recovery box and the heat exchanger, the fresh air and the exhaust air are prevented from crossing, and the air isolation is ensured. In the ventilation mode in the transition season, the exhaust air bypass valve and the fresh air bypass valve are opened, and the exhaust air fan and the fresh air fan are started, so that the fresh air is directly introduced into the indoor, and the exhaust air is directly discharged to the outdoor without starting the recovery device, thereby significantly reducing the energy consumption. In the dehumidification mode in the plum rain season, the state of the exhaust air bypass valve is automatically switched according to the temperature and humidity feedback, so that the dehumidification and reheating functions are accurately realized, and the energy saving efficiency is improved.

[0035] Through the application, the wet membrane heat exchange core is arranged between the water tank at the bottom of the heat recovery box and the heat recovery condenser. The water in the water tank can be pumped into the pre-cooling surface cooler of the fresh air box. In this process, the water is heated in the pre-cooling surface cooler, and the heated water is sprayed at the top end of the wet membrane heat exchange core to exchange heat with the exhaust air. The open cycle is realized, the frequency of external water supplement is reduced, the water temperature is increased after the pre-cooling surface cooler absorbs the heat of the fresh air, and the heat in the exhaust air is absorbed by the spray at the top end of the wet membrane, so that the energy utilization in the primary recovery process is more sufficient. The circulating water pump is detected by the water flow switch and the current, so that the circulating water path is kept unobstructed, the water pump is prevented from idling and clogging, and the system reliability is improved.

[0036] Through the application, the secondary evaporation condensation heat recovery mode is provided. When the temperature of the fresh air supply is still higher than the set value after the primary heat recovery, the four-way valve is kept in the power-off state, the compressor sucks and compresses the low-pressure side refrigerant, and sends it to the heat recovery condenser to exchange heat with the exhaust air. The liquid refrigerant is throttled to the pre-cooling evaporator to exchange heat with the pre-cooled fresh air. In the dehumidification mode in the plum rain season, the four-way valve is connected to the power supply, the high-pressure refrigerant is guided to the reheating condenser, and the dehumidified fresh air is reheated. The refrigerant cooled by the reheating condenser is throttled by the throttling mechanism and then enters the pre-cooling evaporator to dehumidify the fresh air.

[0037] Through the application, the fresh air fan and the exhaust air fan are variable frequency fans, which run at different frequencies according to different modes to achieve energy saving effect. The processor is arranged in the control cabinet, which can process the signals detected by various sensors to ensure the automatic operation of the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a full heat recovery air conditioner mode running structure diagram of the application.

[0039] Figure 2 Schematic diagram of operation structure of the Meiyu season initial mode of the present application.

[0040] Figure 3 Schematic diagram of operation structure of the transition season ventilation mode of the present application.

[0041] Figure 4 Principle diagram of operation of the refrigeration system of the present application.

[0042] Figure 5 Flow chart of the control method of the present application.

[0043] In the figure: 11 - exhaust air box, 12 - exhaust air filter, 13 - exhaust air bypass valve, 14 - exhaust air fan, 21 - heat recovery box, 22 - wet membrane 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 - sub-cooling evaporator, 45 - reheat condenser, 46 - throttling mechanism, 51 - exhaust air temperature and humidity sensor, 52 - fresh air supply temperature and humidity sensor, 53 - air shortage pressure difference 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

[0044] In order to make the technical means, creative characteristics, purposes and effects of the present application easy to understand, the present application will be further described below in combination with specific embodiments. Embodiment 1

[0045] As shown in the figure, a control method of a modular multi-cold-source cascade energy recovery unit. Figures 1-5 In this embodiment, an air conditioner is provided, which comprises an exhaust air unit, a fresh air 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.

[0046] The side of the exhaust air unit is sequentially provided with the heat recovery unit and the fresh air unit. The exhaust air unit comprises an exhaust air bypass valve 13, an exhaust air fan 14, and an exhaust air filter 12; the fresh air unit comprises a fresh air bypass valve 36, a fresh air fan 35, and a fresh air filter 32; the heat recovery unit comprises a water tank 23 and a wet membrane heat exchange core 22; and the energy recovery device comprises a heat recovery condenser 43, a pre-cooling surface cooler 33, a sub-cooling evaporator 44, a reheat condenser 45, a circulating water pump 34, a four-way valve 42, and a compressor 41.

[0047] Referring to

[0048] , Figure 1 ,

[0049] The exhaust fan unit is arranged inside the exhaust box 11, the fresh air fan unit is arranged inside the fresh air box 31, and the heat recovery box 21 is arranged between the exhaust box 11 and the fresh air box 31. The exhaust box 11 is in the shape of a cuboid, the lower end side is provided with an exhaust air inlet, and the top is provided with an exhaust air outlet. The exhaust air can enter the exhaust box 11 from the exhaust air inlet and be guided out of the exhaust box 11 by the exhaust fan 14. The exhaust air can flow into the heat recovery box 21 or not flow into the heat recovery box 21 when it is in the exhaust box 11.

[0050] The bottom of the heat recovery box 21 is provided with a water tank 23, the middle is provided with a wet membrane heat exchange core 22, and the top is provided with a heat recovery condenser 43. The exhaust air flowing into the heat recovery box 21 can pass through the wet membrane heat exchange core 22 and the heat recovery condenser 43 in sequence and then enter the exhaust box 11 again. The inclined heat recovery condenser 43 can increase the contact surface of the exhaust air and the heat recovery condenser 43.

[0051] The fresh air fan unit is arranged inside the fresh air box 31, and the control device is also arranged inside the fresh air box 31. The control device includes a control cabinet 57, and a processor is arranged in the control cabinet. The processor can receive signals and control various devices according to the signals.

[0052] In this embodiment, the exhaust box 11 is provided with an exhaust bypass valve 13 in the middle, the exhaust fan 14 is arranged on the top of the exhaust bypass valve 13, the exhaust fan 14 is provided with a lack of air pressure difference switch 53 on the top, the exhaust filter 12 is arranged on the bottom side of the exhaust box 11, and the exhaust temperature and humidity sensor 51 is arranged on the exhaust filter 12. The compressor 41, the low-voltage switch 54, the high-temperature switch 55, the high-voltage switch 56, and the four-way valve 42 are arranged in sequence from left to right on the inside bottom of the exhaust box 11. The pipeline at the bottom of the exhaust box 11 extends to the bottom of the fresh air box 31, and the circulating water pump 34, the water flow switch 37, the throttling mechanism 46, the reheating condenser 45, the subcooling evaporator 44, and the precooling surface cooler 33 are arranged in sequence from left to right on the inside bottom of the fresh air box 31.

[0053] The heat recovery box 21 is provided between the exhaust air box 11 and the fresh air box 31, the bottom of the heat recovery box 21 is provided with a water tank 23, the middle is provided with a wet membrane heat exchange core 22, and the top is provided with a heat recovery condenser 43. The middle of the fresh air box 31 is provided with a fresh air bypass valve 36, the top is provided with a fresh air fan 35, and a control cabinet 57 is arranged outside the box. A lack of air pressure difference switch 53 is arranged at the top of the fresh air fan 35, and a fresh air supply temperature and humidity sensor 52 is arranged at the fresh air fan 35. The side bottom of the fresh air box 31 is provided with a fresh air filter 32, and the top of the fresh air filter 32 is provided with 58. A processor is arranged in the control cabinet 57, which can receive data detected by various sensors and control various devices according to the detected data.

[0054] In this embodiment, the exhaust air bypass valve 13 and the fresh air bypass valve 36 can be opened or closed, and the state of controlling the exhaust air bypass valve 13 and the fresh air bypass valve 36 can control the flow direction of the exhaust air and the fresh air.

[0055] When the exhaust air bypass valve 13 is closed, the exhaust air enters the bottom of the exhaust air box 11 from the exhaust air filter 12, passes through the heat recovery box 21, enters the top of the exhaust air box 11 from the top of the heat recovery box 21, and is discharged from the exhaust air box 11 by the exhaust air fan 14.

[0056] When the exhaust air bypass valve 13 is opened, the exhaust air enters the bottom of the exhaust air box 11 from the exhaust air filter 12, directly passes through the exhaust air bypass valve 13, and is discharged from the exhaust air box 11 by the exhaust air fan 14.

[0057] 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, and then passes through the pre-cooling surface cooler 33, the re-cooling evaporator 44, the reheating condenser 45, and the throttling mechanism 46 arranged in the bottom of the fresh air box 31, and is discharged from the fresh air box 31 by the fresh air fan 35.

[0058] When the fresh air bypass valve 36 is opened, the 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 by the fresh air fan 35.

[0059] In this embodiment, the operation modes include a full heat recovery air conditioning mode, a transition season ventilation mode, and a plum rain season dehumidification mode.

[0060] In 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 requirement of the fresh air supply temperature in use. When the detected fresh air side temperature is greater than the use temperature setting, the full heat recovery air conditioning mode is started; when the detected fresh air side temperature is less than the use temperature setting, the transition season ventilation mode is started; when the detected fresh air side temperature is less than the use setting temperature, but the humidity is greater than the setting humidity, the dehumidification mode is started.

[0061] In the full heat recovery air conditioning mode: the fresh air bypass valve 36 is closed, the fresh air fan 35 is opened, the fresh air enters the fresh air filter 32 from the bottom of the fresh air box 31, and moves upwards in turn through the pre-cooling surface cooler 33 and the re-cooling evaporator 44, and is discharged from the fresh air box 31 into the use environment through the fresh air fan 35. At the same time, the exhaust air bypass valve 13 in the exhaust air box 11 is closed, and the exhaust air fan 14 is opened.

[0062] The full heat recovery air conditioning mode includes a first heat recovery mode and a second evaporative condensation heat recovery mode. First, the first heat recovery mode is executed, and when the processed fresh air temperature cannot reach the set state, the second evaporative condensation heat recovery mode is started.

[0063] In the first heat recovery mode: the circulating water pump 34 is opened, the exhaust air enters the exhaust air filter 12 from the exhaust air box 11, and the exhaust air enters the heat recovery box 21 from the bottom of the exhaust air box. The exhaust air moves upwards after passing through the wet membrane heat exchange core 22, enters the heat recovery condenser 43, and then enters the exhaust air fan 14, which is discharged outside through the exhaust air fan 14. The circulating water pump 34 draws condensate water from the water tank 23 at the bottom of the heat recovery box 21, and pumps it into the pre-cooling surface cooler 33 in the fresh air box 31 to pre-cool the fresh air. The medium water after being heated is sprayed at the top of the wet membrane heat exchange core 22 in the middle of the heat recovery box 21, and fully exchanges heat and humidity with the exhaust air in the wet membrane heat exchange core 22. The medium water after being cooled is poured into the water tank at the bottom of the heat recovery box, and then enters the water pump again. An open cycle is formed to realize energy recovery, and the exhaust air after fully exchanging heat and humidity in the wet membrane heat exchange core 22 tends to be saturated and flows to the exhaust air fan 11.

[0064] 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 provided with a set temperature.

[0065] The circulating water pump 34 can be frequency-adjusted according to the fresh air supply temperature and the set temperature difference, and in the embodiment, the adjustment range is 25-50 Hz, the temperature difference Δt = fresh air supply temperature - set temperature, and the adjustment period f is 10-60 s, and in the embodiment, the adjustment period f is 30 s. The amplitude a (Hz) of the adjusted frequency is shown in the following table:

[0066]

[0067] After the circulating water pump is started, it runs at a full load 50 Hz frequency, 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 50 Hz frequency; when the temperature difference -0.5 < Δt ≦ 0.5℃, the frequency of the circulating water pump is not adjusted, and it runs at the existing frequency; when the temperature difference -0.5 ≦ Δt < -1℃, the frequency of the circulating water pump is reduced by 1 Hz every other adjustment period (30 s); when the temperature difference -1 ≦ Δt < -1.5℃, the frequency of the circulating water pump is reduced by 3 Hz every other adjustment period (30 s); and as shown in the above table, when the frequency of the circulating water pump is reduced to 25 Hz, the temperature difference Δt < -0.5℃, and then it runs at a frequency of 25 Hz and is not adjusted.

[0068] When the primary heat recovery runs and the fresh air treatment temperature cannot reach the set state, the secondary evaporation and condensation heat recovery system is started, and at this time the four-way valve 42 is not powered on, and the compressor 41 is started. The compressor 41 is provided with refrigerant inside, and the compressor 41 can compress the refrigerant into high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant enters the heat recovery condenser 43, exchanges heat with the exhaust air after wet heat exchange, becomes medium-temperature and high-pressure liquid refrigerant, and then flows into the recooling evaporator 44 after being converted into low-temperature and low-pressure liquid refrigerant by the throttling mechanism 46 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, and the fresh air is cooled and dehumidified in the process and then enters the fresh air fan.

[0069] In the embodiment, the compressor 41 is a variable frequency compressor, which can output power in stages. The compressor 41 adjusts the operating frequency of the compressor 41 according to the detected fresh air supply temperature. The fresh air supply temperature sensor 41 detects the fresh air outlet temperature, compares it with the set temperature, and calculates the temperature difference Δt.

[0070] When the temperature difference 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 -2℃ < Δt ≦ -1℃, the output of the compressor 41 is reduced by 50%; and when the temperature difference Δt ≦ -2℃, the compressor 41 is turned off.

[0071] In this embodiment, the above-mentioned judgment is performed every 3 minutes of operation, avoiding frequent switching caused by short-term temperature difference fluctuations. The output power of the compressor 41 is 0, 50%, and 100%. The compressor 41 can achieve stepwise output according to the real-time temperature difference. When the fresh air approaches the set temperature, only 50% of the power of the compressor 41 is used to maintain the cooling capacity, avoiding overcooling; when the temperature difference is large, the full capacity is used to quickly reduce the temperature. After a 3-minute delay, the operating conditions of the compressor 41 are adjusted to avoid frequent start-stop caused by short-period small fluctuations and improve the service life of the equipment.

[0072] In the transition season ventilation mode, the fresh air bypass valve 36 is opened, and the fresh air fan 35 in the fresh air box 31 is opened. The fresh air passes through the fresh air filter 32 and the fresh air bypass valve 36, enters the fresh air fan 35, and is sent into the use environment through the fresh air fan 35. The exhaust air bypass valve 13 is opened, and the exhaust air fan 14 is opened. The exhaust air enters the exhaust air filter 12, enters the exhaust air fan 14 from the exhaust air bypass valve 13, and is discharged outside through the exhaust air fan 14.

[0073] In the Meiyu season dehumidification mode, the fresh air bypass valve 36 is closed, and the fresh air fan 35 in the fresh air box 31 is opened. The fresh air passes through the fresh air filter 32, the pre-cooling surface cooler 33, the re-cooling evaporator 44, and the re-heating condenser 45, enters the fresh air fan 35, and is sent into the use environment through the fresh air fan 35. In the exhaust air side, the exhaust air bypass valve 13 is opened, and the exhaust air fan 14 is opened. The exhaust air passes through the exhaust air filter 12, enters the exhaust air box 11, and enters the exhaust air fan 14 after flowing through the exhaust air bypass valve 13, and is discharged outside by the exhaust air fan 14. At the same time, the four-way valve 42 is energized, and the compressor 41 is started. 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 enters the re-heating condenser 45 through the four-way valve 42 and exchanges heat with the fresh air after passing through the re-cooling evaporator 44, becoming medium-temperature and high-pressure liquid refrigerant. The medium-temperature and high-pressure liquid refrigerant becomes low-temperature and low-pressure liquid refrigerant after passing through the throttling mechanism 46 and enters the re-cooling evaporator 44. The low-temperature and low-pressure liquid refrigerant exchanges heat with the fresh air passing through the pre-cooling surface cooler 33 through the re-cooling evaporator 44, becoming low-temperature and low-pressure gaseous refrigerant. Subsequently, the low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 41. The fresh air is further dehumidified and then heated by the re-heating condenser 45. The fresh air is converted into a medium-temperature and low-humidity state and then enters the fresh air fan 35, which is sent into the use environment.

[0074] In this embodiment, the fresh air fan 35 and the exhaust air 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 Meiyu season dehumidification mode, and operates at an energy-saving frequency in the transition season ventilation mode.

[0075] In this embodiment, the energy-saving frequency is when the fresh air bypass damper and the exhaust air bypass damper are opened, the air volume is increased, and the frequency of the fan is adjusted to ensure constant air volume.

[0076] The way of adjusting the frequency of the fan includes:

[0077] 1. A fixed frequency is set as the energy-saving frequency;

[0078] 2. The frequency of the fan is controlled according to the air pressure difference, that is, the air pressure difference before and after the fan in the total heat recovery air conditioning mode is used as the control target to determine the operating frequency of the fan;

[0079] 3. The frequency of the fan is controlled according to the control air volume, that is, the air flow rate is detected by the air speed sensor in the air duct, and the flow rate is calculated as the measured air volume, and the controller adjusts the frequency of the fan to make the measured air volume consistent with the set air volume.

[0080] The exhaust air fan 14 operates at rated power in the total heat air conditioning mode, and operates at the energy-saving frequency in the ventilation mode in the transition season and the dehumidification mode in the plum rain season.

[0081] The exhaust air fan 14, the fresh air fan 35 are provided with air shortage pressure difference switches 53 on the air outlet side, which can detect whether the fan is running normally, and the air shortage pressure difference switches 53 can transmit the detected data to the processor in the control cabinet 57, and the processor can process the signals of the two air shortage pressure difference switches 53. When there is a pressure difference signal, the fan is running normally; when there is no pressure difference signal, it is a fault, and an alarm prompt is issued. The operating current of the fresh air fan 35 and the exhaust air fan 14 is detected, and when the operating current is higher than the rated value, the processor issues an alarm prompt for fault feedback.

[0082] 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 perform signal feedback of opening to position and closing to position through the air valve actuators, and when the processor gives an opening valve or closing valve instruction, if no opening to position or closing to position feedback signal is received within the running time, the processor issues an alarm prompt.

[0083] In the primary heat recovery mode, the circulating water pump 34 judges the working state of the water pump through the water flow switch on the water outlet side of the water pump, and can detect the operating current overcurrent detection of itself, and when the operating current is higher than the rated value, the signal is transmitted to the processor, and the processor issues an alarm prompt.

[0084] In the secondary heat recovery mode, the compressor is protected and controlled by the system high pressure, low pressure and high temperature switches, and has operating current overcurrent detection, and when the operating current is higher than the rated value, the signal is transmitted to the processor, and the processor issues an alarm prompt.

[0085] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and such changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A control method for a modular multi-source cascade energy recovery unit, comprising: Exhaust fan units, fresh air units, heat recovery units, energy recovery devices, The heat recovery unit and the fresh air unit are sequentially arranged on the side of the exhaust fan unit. The exhaust fan 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 features are: The fresh air handling unit is equipped with a fresh air intake temperature and humidity sensor, which can detect the temperature and humidity of the fresh air. Based on the results detected by the fresh air intake temperature and humidity sensor, determine and switch to one of the following three operating modes: total heat recovery air conditioning mode, transitional season ventilation mode, and rainy season dehumidification mode. When the fresh air side temperature is higher than the set temperature, the total heat recovery air conditioning mode is activated; when the fresh air side temperature is lower than the set temperature and the humidity is lower than the set humidity, the transitional season ventilation mode is activated; 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 activated. When in total heat recovery air conditioning mode, it includes primary heat recovery and secondary evaporation-condensation recovery. When the fresh air bypass valve is closed and the fresh air fan is turned on, the fresh air passes through the fresh air filter, the pre-cooling surface cooler, and the re-cooling evaporator in sequence before entering the operating environment. Close the exhaust bypass valve and turn on the exhaust fan. The exhaust air passes through the exhaust filter, wet membrane heat exchange core, heat recovery condenser and exhaust fan and is then discharged outdoors. A heat recovery box is installed between the exhaust fan and the fresh air fan. When the fresh air intake temperature is higher than the set temperature When the first-stage heat recovery is started, the circulating water pump draws cooling water from the bottom of the heat recovery box and pumps it into the pre-cooling surface cooler on the fresh air side to cool the fresh air. The water is then sprayed on the top of the wet film heat exchange core and exchanged with the exhaust air for heat and moisture before flowing back to the bottom of the heat recovery box. After being heated by the pre-cooled surface cooler, the medium water in the heat recovery box exchanges heat with the exhaust air from above to below the wet film heat exchange core. The compressor is equipped with refrigerant. When the fresh air intake temperature is higher than the set value, it maintains the first-stage heat recovery operation. When the fresh air supply temperature is higher than the set value, the compressor is started and the four-way valve is kept de-energized, entering the second-stage evaporation and condensation recovery. In two-stage evaporation and condensation recovery: The compressor compresses the refrigerant into a high-temperature, high-pressure gaseous state, which is then converted into a medium-temperature, high-pressure liquid state after heat exchange with the exhaust air in the heat recovery condenser. The refrigerant is throttled through a throttling mechanism, converted into a low-temperature, low-pressure liquid state, and then enters the recooling evaporator to exchange heat with the pre-cooled fresh air. After vaporization, it is drawn into the compressor, which can reduce the temperature and humidity of the fresh air during this process.

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

3. The control method for a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: When in dehumidification mode during the rainy season: The fresh air bypass valve is closed and the fresh air fan is turned on. The fresh air passes through the fresh air filter, the pre-cooling surface cooler, the recooling evaporator, and the reheat condenser in sequence before being output to the air supply side. Open the exhaust bypass valve and turn on the fresh air fan. The exhaust air passes through the exhaust filter and is directly output to the exhaust side. The four-way valve and compressor are started, and the refrigerant completes the heat exchange cycle in the reheat condenser and recooling evaporator in sequence to achieve cooling, dehumidification and reheating of fresh air.

4. The control method for 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 the total heat recovery air conditioning mode, the fresh air fan and the exhaust fan operate at rated power; in the rainy season dehumidification mode, the fresh air fan operates at rated power and the exhaust fan operates at energy-saving frequency; in the transition season ventilation mode, the fresh air fan and the exhaust fan operate at energy-saving frequency.

5. The control method for a modular multi-cold source cascade energy recovery unit according to claim 4, characterized in that: Both the fresh air fan and the exhaust fan are equipped with a detection module. The detection module 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.

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

7. The control method for a modular multi-cold source cascade energy recovery unit according to claim 1, characterized in that: The fresh air unit is equipped with a control device on its side. The control device includes a processor, which is capable of receiving signals and controlling various devices according to the signals.

8. An air conditioner, characterized in that, The control method of the modular multi-cold source cascade energy recovery unit as described in any one of claims 1-7 is used during the operation of the air conditioner.

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