Heat recovery system and control method thereof

Abstract

The present application relates to the technical field of fresh air heat recovery, in particular to a heat recovery system and a control method thereof; in the heat recovery system, the temperature of fresh air of each branch is monitored, the temperature difference of each branch is calculated, and the heat recovery of the corresponding branch is started when the starting temperature difference is met, so that different exhaust air units can accurately cope with different indoor environmental conditions; one set of heat recovery system can be shared by different end environmental conditions, the cost increase of setting multiple systems is reduced, and the heat recovery of each branch can be independently adjusted to realize maximum efficient operation.

Description

Technical Field

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

[0002] As a key device for improving indoor air quality and protecting human health, fresh air systems continuously introduce fresh outdoor air and expel stale indoor air during operation. The temperature difference between fresh and exhaust air leads to significant energy loss, a problem particularly pronounced in scenarios with high air conditioning loads during winter and summer. Therefore, exhaust heat recovery technology, as a core means of reducing the energy consumption of fresh air systems, is gradually gaining popularity. It has become a standard component of fresh air systems in regions with stringent requirements for indoor thermal environment control, such as the frigid north and the warm summers and mild winters of the south, as well as in energy-intensive high-end buildings such as high-end commercial buildings, hotels, medical facilities, and data centers.

[0003] Currently, the control logic of existing heat recovery systems is mostly based on simple start / stop or airflow adjustment using a single parameter (such as fresh air inlet temperature and exhaust air outlet temperature), lacking comprehensive consideration of load changes in multiple areas of the building, dynamic fluctuations in outdoor weather conditions, and the operating status of the heat exchange core. For example, when outdoor temperatures drop sharply in winter, a single heat recovery system may not be able to quickly raise the fresh air temperature, leading to indoor temperature fluctuations; while maintaining high heat exchange efficiency during transitional seasons will result in energy waste. Furthermore, in large buildings with multiple independent fresh air zones, a single heat recovery system struggles to achieve precise heat recovery control for each zone, further reducing the system's energy efficiency and operational flexibility.

[0004] As high-end buildings increasingly demand higher energy efficiency, stability, and intelligence in their fresh air systems, traditional single-unit heat recovery systems can no longer meet practical application needs. Therefore, developing a multi-unit fresh and exhaust air heat recovery system that can adapt to various regional operating conditions, achieve precise heat recovery control, and possess high fault tolerance has become a pressing technical challenge in the field of building ventilation and energy conservation. This is of great significance for promoting the technological upgrading of fresh air systems and improving the overall energy efficiency of buildings. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention aims to provide a heat recovery system and its control method to solve the problem of low heat recovery rate in multiple fresh air handling units and exhaust fan units.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a heat recovery system, including multiple fresh air units and multiple exhaust fan units connected by pipelines, as well as a hydraulic module. Each set of fresh air units and exhaust fan units is equipped with a heat recovery coil. Taking the hydraulic module as the starting and ending point, along the flow direction of the medium in the pipeline, the system consists of, in sequence, a hydraulic module pump post-pressure gauge, a hydraulic module medium circulation flow meter, a medium thermometer flowing from the hydraulic module into the fresh air unit, a medium-side valve of fresh air unit i, a heat recovery coil of fresh air unit i, a medium-side outlet thermometer of fresh air unit i, a medium thermometer returning from the hydraulic module to the fresh air unit, a medium thermometer flowing from the hydraulic module into the exhaust fan unit, a medium-side valve of exhaust fan unit i, a heat recovery coil of exhaust fan unit i, and a medium-side outlet thermometer of exhaust fan unit i. The hydraulic module provides a medium thermometer for the medium flowing into and returning from the exhaust fan unit, and a hydraulic module pre-pump pressure gauge. The pipeline between the hydraulic module medium circulation flow meter and the hydraulic module medium thermometer flowing into the fresh air unit is connected to the pipeline between the hydraulic module medium thermometer flowing into and returning from the fresh air unit and the hydraulic module medium thermometer flowing into the exhaust fan unit via a hydraulic module bypass valve. The inlet and outlet of the heat recovery coil of the fresh air unit i are respectively equipped with a fresh air unit i air-side inlet thermometer, a fresh air unit i air-side outlet thermometer, and a fresh air unit i air volume meter. The inlet and outlet of the heat recovery coil of the exhaust fan unit i are respectively equipped with an exhaust fan unit i air-side inlet thermometer, an exhaust fan unit i air-side outlet thermometer, and an exhaust fan unit i air volume meter.

[0008] Furthermore, the hydraulic module also includes a water pump, a filter, a medium replenishment port, a pressure stabilizing tank, an exhaust port, and a drain port.

[0009] On the other hand, the present invention provides a control method for a heat recovery system, based on the aforementioned heat recovery system;

[0010] Monitor the air inlet temperature T on the air side of the fresh air handling unit air,sup,in,i and the air inlet temperature T of the exhaust fan unit air,exh,in,i ;

[0011] If temperature difference is activated Greater than or equal to the preset summer start-up temperature difference ΔT s1 Or preset the winter start-up temperature difference ΔT s2 If the valve is open, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be opened; otherwise, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be closed.

[0012] Initial opening of the medium-side valve of the fresh air handling unit The initial opening degree of the medium-side valve of the exhaust fan unit i ;

[0013] Adjust the operating power of the water pump within the hydraulic module to make , where C P，air For the specific heat of air at constant pressure, CP，gly For the specific heat at constant pressure of the medium, ρ air ρ is the air density. gly Q is the density of the medium. gly Q represents the circulating flow rate of the hydraulic module medium. air,exh,i i represents the air volume of the exhaust fan unit;

[0014] Monitor the heat exchange temperature difference ΔT of the fresh air respectively sup,i The heat exchange temperature difference ΔT between the exhaust and the air side exh,i , , ;

[0015] If ΔT sup,i If the temperature difference is less than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then reduce the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i If ΔT sup,i If the temperature difference is greater than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then increase the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i Otherwise, maintain the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i constant;

[0016] If ΔT exh,i If the temperature difference is less than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then reduce the opening degree V of the medium-side valve of the exhaust fan unit i. gly,exh,i If ΔT exh,i If the temperature difference exceeds the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then increase the opening degree V of the medium-side valve of the exhaust fan unit i. gly,exh,i Otherwise, maintain the opening degree V of the medium-side valve of exhaust fan unit i. gly,exh,i constant;

[0017] Continuously monitor the start-up temperature difference ΔT si If the temperature difference ΔT is activated si Less than or equal to the preset summer heat exchange temperature difference ΔT s1 -ζ or the preset winter heat exchange temperature difference ΔT2-ζ, then close the medium-side valve of the fresh air unit i and the medium-side valve of the exhaust fan unit i. If the temperature difference ΔT is activated... si Greater than the preset summer heat exchange temperature difference ΔT s1 -ζ or preset winter heat exchange temperature difference ΔT2-ζ, ζ is the start-stop hysteresis of the hydraulic module pump, then reset the initial opening of the medium side valve of fresh air unit i and the medium side valve of exhaust air unit i.

[0018] After closing the medium-side valves of the fresh air handling unit i and the exhaust air handling unit i, determine whether all medium-side valves of the fresh air handling unit i and the exhaust air handling unit i are closed. If not, reset the initial opening of the medium-side valves of the fresh air handling unit i and the exhaust air handling unit i. If yes, shut down the water pump and stop the heat recovery system.

[0019] Furthermore, it also includes monitoring the pressure P1 before the hydraulic module pump and the pressure P2 after the hydraulic module pump, and calculating their pressure difference ΔP; if the pressure difference ΔP is greater than or equal to the high pressure warning value, a high pressure warning is issued and the pump frequency is reduced; if the pressure difference ΔP is greater than or equal to the high pressure shutdown value of the pump, the pump is shut down.

[0020] Furthermore, if the pressure difference ΔP is less than or equal to the low-pressure warning value, a low-pressure warning is issued and the pump frequency is increased; if the pressure difference ΔP is less than or equal to the low-pressure shutdown value of the pump, the pump is shut down.

[0021] Furthermore, it also includes monitoring the outlet temperature of the fresh air unit on the medium side. If it is lower than the low temperature warning temperature, it will indicate the risk of low temperature freezing.

[0022] If the temperature drops below the low-temperature freezing warning temperature, the system will shut down and display the anti-freeze protection message 1.

[0023] Furthermore, it also includes monitoring the air-side inlet temperature and humidity of exhaust fan unit i and the temperature of the medium flowing into the exhaust fan unit from the hydraulic module, and calculating the inflow dew point temperature of exhaust fan unit i; if the inflow dew point temperature of exhaust fan unit i is less than 0℃ and less than the set dew point temperature, the hydraulic module bypass valve is opened and gradually increased to prompt antifreeze protection 2; otherwise, the bypass valve is gradually closed and the prompt is canceled.

[0024] Furthermore, it also includes monitoring the pressure P1 before the hydraulic module pump; when P1 is less than or equal to the pump's minimum suction pressure P... min This indicates that there is a risk of cavitation on the pump inlet blades. The pump frequency is reduced, and the risk of cavitation is indicated.

[0025] The beneficial effects of this invention are as follows: In the heat recovery system of this invention, each branch monitors the fresh and exhaust air temperature of its own branch and calculates the temperature difference between each branch. When the starting temperature difference is met, the heat recovery of the corresponding branch is activated, which can accurately respond to the conditions of different exhaust fan units corresponding to different indoor environmental conditions. It enables different terminal environmental conditions to share a single heat recovery system, reducing the cost increase of setting up multiple separate systems. Moreover, the heat recovery of each branch can be adjusted independently to achieve maximum efficient operation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the heat recovery system of the present invention;

[0027] Figure 2This is a logic diagram of the control method for the heat recovery system of the present invention;

[0028] Wherein, 1 is the hydraulic module; 2 is the pressure gauge after the hydraulic module pump; 3 is the medium circulation flow meter of the hydraulic module; 4 is the medium temperature gauge of the hydraulic module flowing into the fresh air handling unit; 5 is the medium-side valve of fresh air handling unit i; 6 is the heat recovery coil of fresh air handling unit i; 7 is the medium-side outlet temperature gauge of fresh air handling unit i; 8 is the medium temperature gauge of the hydraulic module flowing into the fresh air handling unit and returning; 9 is the medium temperature gauge of the hydraulic module flowing into the exhaust fan unit; 10 is the medium-side valve of exhaust fan unit i; 11 is the exhaust fan unit. 12 is the heat recovery coil; 13 is the outlet thermometer on the medium side of the exhaust fan unit; 14 is the thermometer for the medium flowing from the hydraulic module into the exhaust fan unit and returning; 15 is the pressure gauge before the pump of the hydraulic module; 16 is the bypass valve of the hydraulic module; 17 is the inlet thermometer on the air side of the fresh air unit; 18 is the outlet thermometer on the air side of the fresh air unit; 19 is the inlet thermometer on the air side of the exhaust fan unit; 20 is the outlet thermometer on the air side of the exhaust fan unit; 21 is the air volume meter of the exhaust fan unit. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments.

[0030] It should be noted that these embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Simple improvements to the method under the premise of the present invention are all within the scope of protection claimed by the present invention.

[0031] See Figure 1This invention provides a heat recovery system, comprising multiple fresh air units and multiple exhaust fan units connected by pipes, and a hydraulic module 1. Each fresh air unit and exhaust fan unit is equipped with a heat recovery coil. Taking the hydraulic module as the starting and ending point, along the flow direction of the medium in the pipes, the system consists of: a hydraulic module pump post-pressure gauge 2, a hydraulic module medium circulation flow meter 3, a medium thermometer 4 for the medium flowing into the fresh air unit 1, a medium-side valve 5 for the fresh air unit 1, a heat recovery coil 6 for the fresh air unit 1, a medium-side outlet thermometer 7 for the fresh air unit 1, a medium thermometer 8 for the medium returning from the hydraulic module to the fresh air unit 1, a medium thermometer 9 for the medium flowing into the exhaust fan unit 1, a medium-side valve 10 for the exhaust fan unit 1, a heat recovery coil 11 for the exhaust fan unit 1, and a medium-side outlet thermometer 12 for the exhaust fan unit 1. The medium thermometer 13 flowing into the exhaust fan unit and the pressure gauge 14 before the hydraulic module pump are connected to the medium thermometer flowing into the fresh air unit via the hydraulic module bypass valve 15. The pipe between the medium circulation flow meter of the hydraulic module and the medium thermometer flowing into the fresh air unit is connected to the pipe between the medium thermometer flowing into the fresh air unit and the medium thermometer flowing into the exhaust fan unit via the hydraulic module. The inlet and outlet of the heat recovery coil 6 of the fresh air unit i are respectively equipped with the inlet thermometer 16, the outlet thermometer 17, and the air volume meter 18 of the fresh air unit i. The inlet and outlet of the heat recovery coil 11 of the exhaust fan unit i are respectively equipped with the inlet thermometer 19, the outlet thermometer 20, and the air volume meter 21 of the exhaust fan unit i.

[0032] The system comprises multiple fresh air units and exhaust units. The number of fresh air units and exhaust units can vary; one fresh air unit can correspond to multiple exhaust units, or multiple fresh air units can correspond to one exhaust unit. The specific matching depends on the configuration of the fresh air and exhaust units in the same space / room. Successfully matched fresh air and exhaust units are considered to be on the same branch, meaning the i-th fresh air unit and the i-th exhaust unit form one branch. Alternatively, if the i-th exhaust unit consists of multiple units (i.e., i-1, i-2 exhaust units), they would all be on the same branch as the i-th fresh air unit.

[0033] The heat exchange medium inside the pipe can be a solution of ethylene glycol and propylene glycol.

[0034] The water pump in the hydraulic module drives the heat exchange medium to flow in the pipeline. In the exhaust fan unit, the heat recovery coil transfers the cold and heat in the exhaust air to the heat exchange medium. In the fresh air fan unit, the heat recovery coil transfers the cold and heat in the heat exchange medium to the fresh air, recovering the cold and heat in the exhaust air and pre-cooling and preheating the fresh air to achieve energy saving. The greater the temperature difference between the fresh air and the exhaust air, the greater the air volume and the greater the heat recovery.

[0035] The hydraulic module also includes a water pump, filter, medium replenishment port, pressure stabilizing tank, vent, and drain port.

[0036] See Figure 2 A control method for the aforementioned heat recovery system includes:

[0037] Monitor the air inlet temperature T on the air side of the fresh air handling unit air,sup,in,i and the air inlet temperature T of the exhaust fan unit air,exh,in,i ;

[0038] If temperature difference is activated Greater than or equal to the preset summer start-up temperature difference ΔT s1 Or preset the winter start-up temperature difference ΔT s2 If the valve is open, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be opened; otherwise, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be closed.

[0039] Initial opening of the medium-side valve of the fresh air handling unit The initial opening degree of the medium-side valve of the exhaust fan unit i ;

[0040] Adjust the operating power of the water pump within the hydraulic module to make , where C P，air For the specific heat of air at constant pressure, C P，gly For the specific heat at constant pressure of the medium, ρ air ρ is the air density. gly Q is the density of the medium. gly Q represents the circulating flow rate of the hydraulic module medium. air,exh,i i represents the air volume of the exhaust fan unit;

[0041] Monitor the heat exchange temperature difference ΔT of the fresh air respectively sup,i The heat exchange temperature difference ΔT between the exhaust and the air side exh,i , , ;

[0042] If ΔT sup,i If the temperature difference is less than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2 (specifically compared with the summer or winter heat exchange temperature difference, depending on whether it is summer or winter at that moment), then reduce the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i If ΔT sup,i If the temperature difference is greater than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then increase the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i Otherwise, maintain the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i constant;

[0043] If ΔT exh,i If the temperature difference is less than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then reduce the opening degree V of the medium-side valve of the exhaust fan unit i.gly,exh,i If ΔT exh,i If the temperature difference exceeds the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then increase the opening degree V of the medium-side valve of the exhaust fan unit i. gly,exh,i Otherwise, maintain the opening degree V of the medium-side valve of exhaust fan unit i. gly,exh,i constant;

[0044] Continuously monitor the start-up temperature difference ΔT si If the temperature difference ΔT is activated si Less than or equal to the preset summer heat exchange temperature difference ΔT s1 -ζ or the preset winter heat exchange temperature difference ΔT2-ζ, then close the medium-side valve of the fresh air unit i and the medium-side valve of the exhaust fan unit i. If the temperature difference ΔT is activated... si Greater than the preset summer heat exchange temperature difference ΔT s1 -ζ or preset winter heat exchange temperature difference ΔT2-ζ, ζ is the start-stop hysteresis of the hydraulic module pump, then reset the initial opening of the medium side valve of fresh air unit i and the medium side valve of exhaust air unit i.

[0045] After closing the medium-side valves of the fresh air handling unit i and the exhaust air handling unit i, determine whether all medium-side valves of the fresh air handling unit i and the exhaust air handling unit i are closed. If not, reset the initial opening of the medium-side valves of the fresh air handling unit i and the exhaust air handling unit i. If yes, shut down the water pump and stop the heat recovery system.

[0046] Each branch monitors the fresh and exhaust air temperature of its own branch and calculates the temperature difference between the branches. If the temperature difference is met, the heat recovery of the corresponding branch is activated. This can accurately respond to the different indoor environmental conditions of different exhaust fan units. For example, in summer, even if the exhaust air temperature in some rooms is too high due to different indoor conditions and there is no heat recovery potential, the branch can be shut down immediately without affecting the heat recovery system of other branches.

[0047] In the initial stage of system startup, the initial valve opening of each branch is set according to the air volume ratio of each branch to ensure the fastest initial operation of the system. Then, the valve opening is finely adjusted based on the actual heat exchange temperature difference, so that the entire heat recovery system can always be in the efficient heat exchange range, thereby improving the module heat recovery efficiency.

[0048] Record ΔT i η sup,i η exh,i η total W, W pump The curves showing the changes of six parameters over time serve as a monitoring tool for the overall operation of the heat recovery system; the meanings of each parameter are as follows:

[0049] 1) ΔT iThe preset heat exchange temperature differences ΔT1 and ΔT2 for summer and winter are generally set to 3-6℃. In areas with high humidity in summer, it is recommended to set ΔT1 to a smaller value to avoid excessive condensation of fresh air, which would increase airflow resistance. Additionally, water will be blown out at the outlet of the heat recovery heat exchanger. In this case, it is recommended to install a baffle plate.

[0050] 2) Real-time heat exchange efficiency of the heat recovery heat exchanger in the fresh air handling unit: If the efficiency is too low, the heat exchange temperature difference can be increased appropriately.

[0051] 3) Real-time heat exchange efficiency of the exhaust fan unit's heat recovery heat exchanger: If the efficiency is too low, the heat exchange temperature difference can be increased appropriately.

[0052] 4) Real-time heat exchange efficiency of the entire heat recovery system module: ;

[0053] 5) Real-time heat recovery power of the entire heat recovery system module: ;

[0054] 6) Pump power W of the hydraulic module in the heat recovery system pump .

[0055] The control method also includes: monitoring the pressure P1 before the hydraulic module pump and the pressure P2 after the hydraulic module pump, and calculating their pressure difference ΔP; if the pressure difference ΔP is greater than or equal to the high pressure warning value, a high pressure warning is issued and the pump frequency is reduced; if the pressure difference ΔP is greater than or equal to the high pressure shutdown value of the pump, the pump is shut down.

[0056] If the pressure difference ΔP is less than or equal to the low-pressure warning value, a low-pressure warning will be issued and the pump frequency will be increased; if the pressure difference ΔP is less than or equal to the low-pressure shutdown value of the pump, the pump will be shut down.

[0057] The control methods also include: monitoring the outlet temperature of the fresh air unit i on the medium side, and if it is lower than the low temperature warning temperature, indicating the risk of low temperature freezing;

[0058] If the temperature drops below the low-temperature freezing warning temperature, the system will shut down and display the anti-freeze protection message 1.

[0059] The heat exchange medium may freeze at any time, requiring an emergency shutdown. In other words, under extreme low-temperature conditions in winter in certain regions, the corresponding heat recovery system may not be able to start normally.

[0060] The control method also includes: monitoring the inlet temperature and humidity of the exhaust fan unit i on the air side and the temperature of the medium flowing into the exhaust fan unit from the hydraulic module, and calculating the dew point temperature of the inflow air volume of the exhaust fan unit i; if the dew point temperature of the inflow air volume of the exhaust fan unit i is less than 0℃ and less than the set dew point temperature, the bypass valve of the hydraulic module is opened and gradually increased to prompt the antifreeze protection 2; otherwise, the bypass valve is gradually closed and the prompt is canceled.

[0061] The control method also includes: monitoring the pressure P1 before the hydraulic module pump; when P1 is less than or equal to the pump's minimum suction pressure P... min This indicates that there is a risk of cavitation on the pump inlet blades. The pump frequency is reduced, and the risk of cavitation is indicated.

[0062] The heat recovery system and control method proposed in this application allow different end-point environmental conditions to share a single heat recovery system, reducing the cost increase of setting up multiple separate systems. Furthermore, the heat recovery of each branch can be adjusted independently to achieve maximum efficient operation.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A control method of a heat recovery system, characterized by, Based on the heat recovery system, the heat recovery system includes a plurality of fresh air units and a plurality of exhaust air units connected by pipes and a hydraulic module, each set of fresh air unit and exhaust air unit is provided with heat recovery coil; With the hydraulic module as the starting and ending point, the flow direction of the medium in the pipeline is hydraulic module pump pressure gauge, hydraulic module medium circulation flow meter, hydraulic module inflow fresh air unit medium temperature meter, fresh air unit i medium side valve, fresh air unit i heat recovery coil, fresh air unit i medium side outlet temperature meter, hydraulic module inflow fresh air unit return medium temperature meter, hydraulic module inflow exhaust air unit medium temperature meter, exhaust air unit i medium side valve, exhaust air unit i heat recovery coil, exhaust air unit i medium side outlet temperature meter, hydraulic module inflow exhaust air unit return medium temperature meter and hydraulic module pump front pressure gauge, the pipeline between the hydraulic module medium circulation flow meter and the hydraulic module inflow fresh air unit medium temperature meter is communicated with the pipeline between the hydraulic module inflow fresh air unit return medium temperature meter and the hydraulic module inflow exhaust air unit medium temperature meter by setting hydraulic module bypass valve; The air inlet and air outlet of the fresh air unit i heat recovery coil are respectively provided with fresh air unit i air side inlet temperature meter, fresh air unit i air side outlet temperature meter and fresh air unit i air flow meter, and the air inlet and air outlet of the exhaust air unit i heat recovery coil are respectively provided with exhaust air unit i air side inlet temperature meter, exhaust air unit i air side outlet temperature meter and exhaust air unit i air flow meter; Monitoring the fresh air unit i wind side inlet temperature T air,sup,in,i And exhaust air unit i wind side inlet temperature T air,exh,in,i ; If temperature difference is activated Greater than or equal to the preset summer start-up temperature difference ΔT s1 Or preset the winter start-up temperature difference ΔT s2 If the valve is open, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be opened; otherwise, the corresponding valve on the medium side of the fresh air handling unit i and the valve on the medium side of the exhaust air handling unit i will be closed. Initial opening degree of medium side valve of fresh air handling unit i Initial opening degree of medium side valve of exhaust air handling unit i ; Adjusting the running power of the water pump in the water power module, so that Where C P，air is the specific heat of air at constant pressure, C P，gly is the specific heat of medium at constant pressure, p air is the density of air, p gly is the density of medium, Q gly is the circulating flow of the water power module medium, Q air,exh,i is the air volume of the exhaust fan unit i; The fresh air side heat transfer temperature difference ΔT sup,i and the exhaust air side heat transfer temperature difference ΔT exh,i , , ; If ΔT sup,i If the temperature difference is less than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then reduce the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i If ΔT sup,i If the temperature difference is greater than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, then increase the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i Otherwise, maintain the opening degree V of the medium-side valve of the fresh air unit i. gly,sup,i constant; If ΔT exh,i is less than a preset summer heat exchange temperature difference ΔT1 or a preset winter heat exchange temperature difference ΔT2, the medium side valve opening degree V gly,exh,i of the exhaust fan unit i is decreased. exh,i If ΔT gly,exh,i is greater than the preset summer heat exchange temperature difference ΔT1 or the preset winter heat exchange temperature difference ΔT2, the medium side valve opening degree V gly,exh,i of the exhaust fan unit i is increased. Otherwise, the medium side valve opening degree V of the exhaust fan unit i is kept unchanged. Monitoring the start-up temperature difference ΔT si , if the start-up temperature difference ΔT si is less than or equal to the preset summer heat exchange temperature difference ΔT s1 -ζ or the preset winter heat exchange temperature difference ΔT2-ζ, then the fresh air handling unit i medium side valve and the exhaust air handling unit i medium side valve are closed, if the start-up temperature difference ΔT si is greater than the preset summer heat exchange temperature difference ΔT s1 -ζ or the preset winter heat exchange temperature difference ΔT2-ζ, ζ is the hydraulic module water pump start-stop hysteresis, then the initial opening of the fresh air handling unit i medium side valve and the exhaust air handling unit i medium side valve is reset; After the fresh air unit i medium side valve and the exhaust air unit i medium side valve are closed, it is judged whether all fresh air unit i medium side valves and exhaust air unit i medium side valves are closed, if not, the initial opening of the fresh air unit i medium side valve and the exhaust air unit i medium side valve is reset, if yes, the water pump is closed, and the heat recovery system stops running.

2. The control method of a heat recovery system according to claim 1, characterized by, The hydraulic module further comprises a water pump, a filter, a medium liquid supplement port, a pressure stabilizing tank, an exhaust port and a blowdown port.

3. The control method of a heat recovery system according to claim 1, characterized by, The hydraulic module further comprises a water pump, a filter, a medium liquid supplement port, a pressure stabilizing tank, an exhaust port and a blowdown port.

4. The control method of a heat recovery system according to claim 3, characterized by, If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed.

5. The control method of a heat recovery system according to claim 4, characterized by, If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed. If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed.

6. The control method of a heat recovery system according to claim 5, characterized by, If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed. If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed. If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed. If the pressure difference ΔP is less than or equal to the low pressure warning value, a low pressure warning is carried out, and the frequency of the water pump is increased; if the pressure difference ΔP is less than or equal to the water pump low pressure closing value, the water pump is closed.

7. The control method of a heat recovery system according to claim 6, characterized by, Also included is monitoring the hydraulic module pump pre-pressure P1, when P1 is less than or equal to the water pump minimum suction pressure P min , that is, the water pump inlet blade is at risk of cavitation, the water pump is reduced in frequency, and the cavitation risk is prompted.

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