Energy-saving fresh air system suitable for high-temperature and high-humidity areas and control method

Abstract

The invention relates to an energy-saving fresh air system suitable for a high-temperature and high-humidity area and a control method. The energy-saving fresh air system comprises a filter, a heat exchanger, a surface air cooler and a fan which are sequentially arranged on an air pipe. Outdoor fresh air enters the heat exchanger through the filter, the heat exchanger precools the filtered fresh air with dehumidification cold air from the surface air cooler as a cold source, and the precooled fresh air is subjected to deep cooling dehumidification through the surface air cooler, reheated through the heat exchanger and finally fed into a room through the draught fan. A branch pipe is arranged between the filter and the heat exchanger, filtered fresh air is led out of the branch pipe to be fed into the surface air cooler, and the amount of the fresh air fed into the surface air cooler is controlled through a bypass air valve. And the other part of fresh air controls the fresh air volume fed into the heat exchanger through the pre-cooling air valve, the circulation path and the heat exchange proportion of the fresh air are controlled through linkage of the bypass air valve and the pre-cooling air valve, and air supply temperature adjustment is achieved. And the fresh air is pre-cooled by using the cold air after deep dehumidification, and meanwhile, the dehumidified low-temperature cold air is reheated, so that the energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of fresh air units, and in particular to an energy-saving fresh air system and a control method suitable for high-temperature and high-humidity areas. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In high-temperature and high-humidity regions, the wet load accounts for a significant portion of the fresh air system. This places greater pressure on fresh air units to meet indoor air quality and dehumidification requirements while also increasing the system's operational burden. Furthermore, to prevent condensation indoors, the cooled and dehumidified fresh air typically needs to be reheated before being delivered indoors. Traditional fresh air units' heat and moisture management methods result in a cold-heat offset, further increasing their energy consumption. Furthermore, conventional fresh air units lack effective intelligent control mechanisms, preventing on-demand fresh air delivery and hindering comprehensive system optimization. Summary of the Invention

[0004] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides an energy-saving fresh air system and control method suitable for high temperature and high humidity areas. The cold air after deep dehumidification is used to pre-cool the fresh air to reduce the load of the surface cooler. At the same time, the heat of the fresh air before pre-cooling is used to reheat the low-temperature cold air after dehumidification, which not only reduces the dehumidification load of the surface cooler, but also avoids condensation caused by directly sending cold air into the room.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A first aspect of the present invention provides an energy-saving fresh air system suitable for high-temperature and high-humidity areas, comprising a filter, a heat exchanger, a surface cooler, and a fan sequentially arranged on an air duct; outdoor fresh air passes through the filter and enters the heat exchanger; the heat exchanger pre-cools the filtered fresh air using dehumidified cold air from the surface cooler as a cooling source; the pre-cooled fresh air is deep-cooled and dehumidified by the surface cooler, reheated by the heat exchanger, and finally delivered to the room by the fan; A branch pipe is provided between the filter and the heat exchanger, which leads the filtered fresh air to the front of the surface cooler, and controls the amount of fresh air sent to the surface cooler through a bypass air valve; another part of the fresh air is controlled by the pre-cooling air valve to control the amount of fresh air sent to the heat exchanger, and the bypass air valve and the pre-cooling air valve are linked to control the flow path and heat exchange ratio of the fresh air to achieve air supply temperature regulation.

[0006] Furthermore, the heat exchanger uses the dehumidified cold air from the surface cooler as the cold source to pre-cool the filtered fresh air. The dehumidified cold air releases cold energy and then heats up, achieving reheating of the fresh air after dehumidification.

[0007] Furthermore, the surface cooler uses circulating cold water as a cold source to perform deep cooling and dehumidification for the fresh air, and uses a control valve to adjust the circulation volume of the cold water.

[0008] A second aspect of the present invention provides a control method for an energy-saving fresh air system suitable for high temperature and high humidity areas, comprising the following steps: Fresh air volume control: By obtaining the carbon dioxide concentration and the number of people in the target room, the amount of fresh air that needs to be increased or decreased is calculated. Combined with the fan's operating frequency and rated air volume, the control signal that the fan responds to the air volume change is determined; Supply air temperature control: The dew point temperature is calculated based on the temperature and humidity of each target room. The sum of the maximum dew point temperature and the set margin is used as the supply air temperature set value. The pre-cooling air valve and the bypass air valve are linked to adjust the opening to maintain the current supply air temperature close to the set value. Humidity control: Determine the maximum humidity based on the humidity of each target room, use the difference between the maximum humidity and the set humidity as the feedback signal, adjust the cold source circulation volume of the surface cooler, and maintain the fresh air humidity within the set range.

[0009] Furthermore, the carbon dioxide concentration in the target room is obtained, and the weighted average concentration value is obtained through weighted processing. According to the deviation from the preset target concentration, the frequency increment control signal u of the fresh air fan is generated. f1 .

[0010] Furthermore, the number of people in the target room is obtained, and the amount of fresh air that needs to be increased or decreased is determined based on the number of people changing. The fan frequency increment control signal u is determined based on the fan power frequency and rated air volume. f2 .

[0011] Furthermore, the new fan frequency increment control signal u f1 with u f2 After summing, it is used as the control signal of the fan.

[0012] Furthermore, the temperature and humidity of each target room are obtained, the dew point temperature of the corresponding room is calculated based on the approximate method, and the maximum dew point temperature is determined. The sum of the maximum dew point temperature and the margin is used as the optimal setting value of the supply air temperature.

[0013] Furthermore, the temperature at the fan outlet is used as the supply air temperature, and compared with the obtained optimal supply air temperature setting value to obtain a deviation signal, and an adjustment signal is generated to adjust the opening of the pre-cooling air valve and the bypass air valve.

[0014] Furthermore, the humidity of each target room is obtained to determine the maximum humidity. The difference between the maximum humidity and the set humidity is used as a feedback signal to adjust the cold water circulation volume of the surface cooler to maintain the fresh air humidity within the set range.

[0015] Compared with the existing technology, one or more of the above technical solutions have the following beneficial effects: 1. After using the surface cooler for dehumidification, traditional fresh air units generally use electric heating to achieve reheating before sending it indoors to avoid condensation in the room due to the low temperature of the dehumidified air. In this method, there is a heat offset between cooling and dehumidification and reheating after dehumidification, which makes the energy consumption of the unit too high. This system has an optimized structural design, using the cold air after deep dehumidification to pre-cool the fresh air, reducing the load of the surface cooler. At the same time, the heat of the fresh air before pre-cooling is used to reheat the low-temperature cold air after dehumidification, which not only reduces the dehumidification load of the surface cooler, but also avoids condensation caused by directly sending cold air into the room. At the same time, it better utilizes the existing heat in the ambient air in high temperature and high humidity areas, reduces system energy consumption, and forms an energy-saving unit.

[0016] 2. This system introduces filtered fresh air into the dehumidification surface cooler through a bypass branch pipe. Through the linkage control of the pre-cooling air valve and the bypass air valve, the flow path and heat exchange ratio of the cold air are changed, thereby achieving precise air supply temperature regulation.

[0017] 3. Multi-strategy control. The system implements a triple control strategy based on indoor environmental parameters: fresh air volume control, supply air temperature control, and humidity control. While meeting air quality requirements, it precisely adjusts fresh air volume, supply air temperature, and indoor humidity to avoid energy waste.

[0018] 4. Fan variable frequency operation optimization. Dynamically adjust fan frequency based on fresh air load forecasts. Compared to traditional fixed-frequency operation, variable frequency control optimizes speed based on real-time demand, ensuring that air supply matches actual usage and reducing ineffective operating energy consumption.

[0019] 5. Wide adaptability. Not only is it suitable for centralized fresh air systems in high-temperature and high-humidity areas, it also has good modularity and scalability, adapting to a variety of scenarios with high requirements for air quality and energy conservation, such as commercial buildings, office buildings, subways, and hospitals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 This is a schematic structural diagram of an energy-saving fresh air system suitable for high-temperature and high-humidity areas, provided by one or more embodiments of the present invention; Figure 2 It is a schematic diagram of the fresh air treatment process of the prior art; Figure 3 is a schematic diagram of a fresh air treatment process provided by one or more embodiments of the present invention; Figure 4This is a schematic diagram of the control principle of an energy-saving fresh air system suitable for high temperature and high humidity areas provided by one or more embodiments of the present invention.

[0022] In the figure: 1 filter; 2 bypass air valve; 3 pre-cooling air valve; 4 heat exchanger; 5 electric valve; 6 surface cooler; 7 fan. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0025] "High temperature and high humidity areas" generally refer to environments with both high temperature and high relative humidity. The specific range may vary depending on the application scenario (such as construction, agriculture, industry, etc.). Generally, the following standards can be used as a reference: High temperature threshold: daily average temperature ≥ 28°C, or daily maximum temperature continuously ≥ 30°C (some standards may require ≥ 35°C to be defined as extreme high temperature); High humidity threshold: Relative humidity (RH) ≥ 70% (long-term average), or dew point temperature (indicating absolute humidity) ≥ 22°C (a key indicator of feeling hot and stuffy).

[0026] In light of the characteristics of high-temperature, high-humidity climates, and in conjunction with regional centralized cooling, the following embodiment presents an energy-saving fresh air system suitable for these regions. This system utilizes a heat recovery heat exchanger to exchange heat between outdoor fresh air and deeply dehumidified cold air, achieving both fresh air pre-cooling and cold air reheating. Furthermore, a control method for this system is proposed, combining precise control strategies for supply air temperature, humidity, and fresh air volume with environmental parameters of the air-conditioned room and occupant information. This strategy aims to comprehensively optimize the energy efficiency of the fresh air system, providing new insights for the energy-saving application of fresh air units in high-temperature, high-humidity regions.

[0027] Example 1: like Figure 1 As shown, the energy-saving fresh air system suitable for high temperature and high humidity areas includes a filter 1, a heat exchanger 4, a surface cooler 6, and a fan 7 arranged in sequence on the air duct; outdoor fresh air enters the heat exchanger 4 through the filter 1, and the heat exchanger 4 uses the dehumidified cold air from the surface cooler 6 as a cold source to pre-cool the filtered fresh air. The pre-cooled fresh air is deep-cooled and dehumidified by the surface cooler 6, and is reheated by the heat exchanger 4, and finally delivered into the room through the fan 7; A branch pipe is provided between the filter 1 and the heat exchanger 4, which leads the filtered fresh air to the front of the surface cooler 6, and controls the amount of fresh air sent to the surface cooler 6 through the bypass air valve 2; another part of the fresh air is controlled by the pre-cooling air valve 3 to send the fresh air volume to the heat exchanger 4, and the bypass air valve 2 and the pre-cooling air valve 3 are linked to control the flow path and heat exchange ratio of the fresh air, so as to achieve precise adjustment of the supply air temperature.

[0028] The working principle of the above system includes filtration link, heat exchange pre-cooling link, deep cooling and dehumidification link, cold air reheating link and air supply link.

[0029] The heat exchanger is responsible for realizing the heat exchange between fresh air and deeply dehumidified cold air, and has the dual functions of pre-cooling and reheating. It uses the cold air after deep dehumidification to pre-cool the fresh air, and at the same time reheats the low-temperature cold air, thereby reducing the subsequent dehumidification load and avoiding condensation caused by directly sending cold air into the room.

[0030] Filtration stage: Outdoor air is first purified through filter 1 to remove suspended particles and impurities, ensuring that the air quality entering the system meets the design standards.

[0031] Heat exchange pre-cooling: Purified fresh air is directed to heat exchanger 4, where it undergoes indirect heat exchange with the low-temperature cold air from the dehumidification section. This heat exchange process not only pre-cools the fresh air, reducing the cooling load of the subsequent dehumidification section, but also heats the low-temperature cold air, achieving its reheating function.

[0032] Furthermore, in order to achieve flexible adjustment, this link is provided with a pre-cooling air valve 3 and a bypass air valve 2, which control the flow path and heat exchange ratio of the cold air through the linkage of the two, thereby achieving precise adjustment of the supply air temperature.

[0033] Deep cooling and dehumidification: After preliminary pre-cooling, fresh outdoor air enters the deep cooling stage. Within the surface cooler 6, the fresh air exchanges heat with low-temperature cold water supplied from the equipment room through the walls of the cold water pipes. A motorized valve controls the cold water flow, lowering the fresh air temperature while achieving dehumidification through deep cooling.

[0034] Cold air reheating link: Since the low-temperature cold air at the outlet of the surface cooler 6 is relatively low, it is easy to cause condensation if it is directly sent into the room. Therefore, the cold air is reintroduced into the heat exchanger 4 to exchange heat with the newly entered outdoor fresh air with a higher temperature, so that the low-temperature cold air is heated to above the indoor dew point temperature.

[0035] Air supply link: The fresh air after reheating is delivered to each room by the fan, meeting the designed air supply temperature, humidity and fresh air volume indicators, and achieving high-quality and efficient indoor air supply.

[0036] like Figure 2As shown in the figure, the traditional fresh air treatment is reheated by electric heating after dehumidification in the surface cooler. This system has been structurally optimized, such as Figure 3 As shown in the figure, in the heat exchange link, the cold air after deep dehumidification is used to pre-cool the fresh air, and at the same time the low-temperature cold air is reheated, thereby reducing the subsequent dehumidification load and avoiding condensation caused by the cold air being directly sent into the room.

[0037] Example 2: like Figure 4 As shown, the control method of the energy-saving fresh air system suitable for high temperature and high humidity areas includes: (1) Fresh air volume control: Carbon dioxide sensors and occupancy detection sensors are installed in each room to collect information on the CO2 concentration and number of people in each room. A mechanism for controlling the fan frequency based on the number of people and CO2 concentration is established to accurately control the fresh air volume and avoid excessive ventilation and energy waste.

[0038] Furthermore, each room is equipped with a carbon dioxide (CO2) sensor and a occupancy detection sensor to monitor the indoor CO2 concentration and the number of people in real time, and upload the data to the edge controller.

[0039] Furthermore, the edge controller performs a weighted average of the CO2 concentration in each room according to the following formula to obtain a weighted average CO2 concentration value: ; Where: C i For the i Carbon dioxide concentration in each room, ppm; A i For the i Area of ​​the room, m 2 ; n The total number of rooms.

[0040] The obtained CO2 weighted average concentration value is input into the CO2 concentration fresh air volume controller. According to the deviation between the weighted average concentration and the preset target concentration, the fresh air fan frequency increment control signal u is generated according to the first feedback control law. f1 .

[0041] Furthermore, the occupancy detection sensor monitors the change in the number of occupants in each room in real time, inputs the occupancy detection information into the occupancy fresh air volume controller, and predicts the required increase in fresh air volume based on the current increase in the number of occupants according to the following formula: ; Where: Δ V The required fresh air volume corresponding to the current number of personnel increase, m 3 / h; V personThe fresh air volume required per person, m 3 / h; Δ N current Adds count to the real-time people in the room.

[0042] According to the required fresh air volume corresponding to the current number of personnel increase, combined with the fan power frequency, the output frequency increment signal u of the fresh air volume controller with the number of personnel is obtained. f2 , to ensure that indoor air quality is guaranteed when there is a surge in the number of people, as shown in the following formula: ; Where: Δ f is the fan frequency increment, Hz; f 0 is the fan power frequency, 50Hz; V 0 is the rated air volume of the fan at the working frequency, m 3 / h.

[0043] Furthermore, the CO2 concentration fresh air volume controller outputs u f1 The output of fresh air volume controller u is related to the number of people f2 After summing, they jointly drive the fan inverter to adjust the frequency, achieving fast and accurate control of the fresh air volume.

[0044] (2) Supply air temperature control: The dew point temperature is calculated in real time based on the room temperature and humidity sensor, and the supply air temperature setting value is optimized according to the dew point temperature to avoid condensation; the target supply air temperature is achieved by adjusting the opening of the pre-cooling air valve and the bypass air valve.

[0045] Furthermore, the supply air temperature setting value optimization method is as follows: the temperature and humidity sensors in each room monitor the indoor temperature and humidity in real time, and upload the detection data to the edge controller. The dew point temperature of each room is calculated using the Magnus-Tetens approximation method, and the maximum dew point temperature is obtained through the high value selector. Based on this dew point temperature, a margin of 1°C is added as the optimal supply air temperature setting value.

[0046] The Magnus-Tetens approximation method is used to calculate the dew point temperature, as shown below: ; ; Where: is the dew point temperature, °C; T is the temperature, °C; H is the relative humidity, %; It is an intermediate function calculated by temperature and humidity; the values ​​of constants A and B are 17.27 and 237.7 respectively.

[0047] Furthermore, the temperature sensor at the fan outlet monitors the supply air temperature in real time. By feeding back the supply air temperature in real time, the deviation signal e is obtained by comparing it with the optimal supply air temperature setting value, and the adjustment signal is generated according to the second feedback control law. u va , adjust the opening of the pre-cooling air valve and the bypass air valve to ensure that the low-temperature fresh air can exchange heat with sufficient outdoor high-temperature fresh air, and ultimately make the supply air temperature reach the target temperature.

[0048] (3) Humidity control: Collect the humidity of each room, select the difference between the highest humidity and the set humidity as the feedback signal, adjust the opening of the cold water valve of the surface cooler, and accurately control the indoor humidity to avoid dampness or over-dryness.

[0049] Furthermore, the humidity sensor in each room monitors the room humidity in real time and uploads the data to the edge controller. After receiving the humidity data uploaded by all sensors, the edge controller selects the maximum humidity value through the high value selector and calculates the difference between it and the preset humidity set point. The adjustment signal is generated based on the deviation e and the third feedback control law. u vw , control the electric regulating valve on the low-temperature cold water pipe, and accurately adjust the air humidity in the room by adjusting the cold water flow.

[0050] Multi-strategy control: This embodiment proposes a triple control strategy based on indoor environmental parameters: fresh air volume control, supply air temperature control, and humidity control. While meeting air quality requirements, it accurately adjusts the fresh air volume, supply air temperature, and indoor humidity to avoid energy waste.

[0051] Fan variable frequency operation optimization: This embodiment dynamically adjusts fan frequency based on fresh air load forecasts. Compared to traditional fixed-frequency operation, variable frequency control optimizes speed based on real-time demand, ensuring that air volume supply matches actual usage and reducing inefficient operating energy consumption.

[0052] Wide adaptability: This fresh air unit is not only suitable for centralized fresh air systems in high temperature and high humidity areas, but also has good modularity and scalability, and is suitable for a variety of commercial buildings, office buildings, subways, hospitals and other scenarios with high requirements for air quality and energy saving.

[0053] Energy savings calculation for heat recovery in the pre-cooling process. This energy-saving calculation is based on a building's fresh air unit in a typical high-temperature, high-humidity region (e.g., Guangdong Province). Specific parameters for the building's fresh air unit are shown in Table 1.

[0054] Table 1 Fresh air unit parameters

[0055] The area is located in a high temperature and high humidity region. The design parameters of outdoor dry-bulb temperature are between 32℃ and 36℃, and the relative humidity is between 70% and 90%. Therefore, the outdoor air state is taken as 35℃ dry-bulb temperature and 75% relative humidity. In GB 50736-2012 "Design Code for Heating, Ventilation and Air Conditioning of Civil Buildings", it is stipulated that the indoor design temperature in summer is between 24℃ and 26℃, and the relative humidity is between 50% and 60%.

[0056] Based on the above situation, the room design temperature is 26℃ and the relative humidity is 60%. According to the Magnus-Tetens approximation method, the room dew point temperature is calculated to be 17.62℃. Adding a margin of 1℃, the outlet temperature is 18.62℃.

[0057] Assume that the fresh air mass flow rate is Point A represents the initial fresh air state, and Point B represents the mixed fresh air state after bypassing. The heat exchange section bypasses on demand, so bypass is not considered for now. To meet dehumidification requirements, the fresh air unit typically dehumidifies and cools the outdoor fresh air to approximately 14°C (95% relative humidity) in engineering design and application. Therefore, 14°C is used here to calculate the energy savings.

[0058] The formula for sensible heat exchange is: ; ; ; The latent heat exchange formula is: ; ; Calculation formula for moisture content and saturated water vapor pressure: ; ; Where: , , , is the state point temperature, °C; , is the sensible heat exchange capacity of the heat exchange section and the surface cooling section, kW; c p is the specific heat capacity of dry air, ; is the relative humidity of air, %; is the saturated water vapor pressure, Pa; is the total air pressure, Pa; is the latent heat of vaporization of water vapor, kJ / kg; is the moisture content at the state point, ; , is the latent heat exchange capacity of the heat exchange section and the surface cooling section, kW.

[0059] According to the above formula, the energy consumption of the fresh air unit is: .

[0060] like Figure 2 As shown, the energy consumption of the traditional fresh air system is determined as: ; .

[0061] Compared with the traditional fresh air system, the energy saving rate of the fresh air unit proposed in this solution is: .

[0062] Energy saving analysis of fan variable frequency control.

[0063] (1) Calculation of energy consumption of traditional fixed-frequency system. Before the transformation, all fans were operated at fixed frequency, and the operating time was from 9:00 to 23:00, the frequency was maintained at 40Hz, and the corresponding air volume was 80% of the rated air volume. Therefore, the fan flow at 40Hz is: ; Where, is the flow rate of the fan at 40Hz, is the maximum flow rate of the fan.

[0064] The power of the fan is proportional to the cube of the air volume. According to the cube law, the relationship between the change of fan power and the change of air volume is: ; Where, P 额定 is the rated frequency of the fan, kW; V is the amount of fresh air required for the room m 3 / h; V 额定 is the maximum air volume of the fan, m 3 / h; Therefore, the fixed frequency operation power is: .

[0065] Since the operating time is 14 hours, the total energy consumption at fixed frequency is: .

[0066] (2) Calculation of energy consumption of the variable frequency drive system. After the renovation, each floor and each household of the building was equipped with a carbon dioxide sensor and a personnel detection device. Based on the indoor carbon dioxide concentration and the number of people from 9:00 to 23:00 on a certain day, the fan frequency at each moment can be calculated according to the fresh air volume controller. In building air conditioning systems, to ensure the normal operation and long-term reliability of the fan, the fan's variable frequency drive system is usually set with a minimum operating frequency lower limit, and the lower limit is generally set at 20-30 Hz. Here, the fan frequency lower limit is 30Hz. The fan frequency in each time period is shown in Table 2 below.

[0067] Table 2 Fan frequency in each time period

[0068] The formula for fan frequency and fan power in each time period is: ; Where, is the power in each period, kW; is the frequency of each time period, Hz.

[0069] The energy consumption formula for each period is: .

[0070] According to the above calculation, the total energy consumption at all times is: .

[0071] The energy saving rate after fan frequency conversion is: .

[0072] The above results show that by rationally designing the heat recovery structure and adopting a multi-strategy control method, the fresh air unit of this scheme can achieve significant energy saving and carbon reduction effects in high temperature and high humidity areas.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. Energy-saving fresh air system suitable for high temperature and high humidity areas, characterized by: It includes filters, heat exchangers, surface coolers and fans arranged in sequence on the air duct; outdoor fresh air enters the heat exchanger through the filter, and the heat exchanger uses the dehumidified cold air from the surface cooler as the cold source to pre-cool the filtered fresh air. The pre-cooled fresh air is deep-cooled and dehumidified by the surface cooler, and reheated by the heat exchanger, and finally sent into the room through the fan.

2. The energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 1, characterized in that: A branch pipe is provided between the filter and the heat exchanger, and the branch pipe leads the filtered fresh air to the front of the surface cooler, and controls the amount of fresh air sent to the surface cooler through a bypass air valve; another part of the fresh air is controlled by the pre-cooling air valve to control the amount of fresh air sent to the heat exchanger, and the bypass air valve and the pre-cooling air valve are linked to control the flow path and heat exchange ratio of the fresh air to achieve air supply temperature regulation.

3. The energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 1, characterized in that: The surface cooler uses circulating cold water as a cold source to perform deep cooling and dehumidification for fresh air, and uses a control valve to adjust the circulation amount of cold water.

4. A control method for an energy-saving fresh air system in high temperature and high humidity areas according to claims 1-3, characterized in that: The following steps are involved: Fresh air volume control: By obtaining the carbon dioxide concentration and the number of people in the target room, the amount of fresh air that needs to be increased or decreased is calculated. Combined with the fan's operating frequency and rated air volume, the control signal that the fan responds to the air volume change is determined; Supply air temperature control: The dew point temperature is calculated based on the temperature and humidity of each target room. The sum of the maximum dew point temperature and the set margin is used as the supply air temperature set value. The pre-cooling air valve and the bypass air valve are linked to adjust the opening to maintain the current supply air temperature close to the set value. Humidity control: Determine the maximum humidity based on the humidity of each target room, use the difference between the maximum humidity and the set humidity as the feedback signal, adjust the cold source circulation volume of the surface cooler, and maintain the fresh air humidity within the set range.

5. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 4, characterized in that: Obtain the carbon dioxide concentration in the target room, obtain the weighted average concentration value through weighted processing, and generate the fresh air fan frequency increment control signal u according to the deviation from the preset target concentration f1 .

6. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 5, characterized in that: Get the number of people in the target room, determine the amount of fresh air that needs to be increased or decreased based on the number of people changing, and determine the fan frequency increment control signal u based on the fan's power frequency and rated air volume. f2 .

7. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 6, characterized in that: The new fan frequency increment control signal u f1 With the fan control signal u f2 After summing, it is used as the control signal of the fan.

8. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 4, characterized in that: Obtain the temperature and humidity of each target room, calculate the dew point temperature of the corresponding room based on the approximate method, and determine the maximum dew point temperature. The sum of the maximum dew point temperature and the margin is used as the optimal setting value of the supply air temperature.

9. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 4, characterized in that: The temperature at the fan outlet is used as the supply air temperature, and compared with the obtained optimal supply air temperature setting value to obtain a deviation signal, and an adjustment signal is generated to adjust the opening of the pre-cooling air valve and the bypass air valve.

10. The control method of the energy-saving fresh air system suitable for high temperature and high humidity areas according to claim 4, characterized in that: The humidity of each target room is obtained to determine the maximum humidity. The difference between the maximum humidity and the set humidity is used as a feedback signal to adjust the cold water circulation volume of the surface cooler to maintain the fresh air humidity within the set range.

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