A purification air conditioning system and control method based on fresh air natural cooling source

Abstract

This invention discloses a purification air conditioning system and control method using a fresh air natural cooling source, comprising a purification air conditioning unit assembly, an air duct assembly, a water duct assembly, and a control system. The air duct assembly connects the purification air conditioning unit assembly to the cleanroom. The water duct assembly provides refrigerant and heat transfer medium to the purification air conditioning unit assembly. The air duct assembly includes a supply air duct, a return air duct, and a fresh air duct. An exhaust air duct is provided between the return air duct and the purification air conditioning unit assembly. The system employs a parallel connection of exhaust fans and supply fans. Based on the performance parameters of the exhaust fans, such as air volume and air pressure, a variable frequency drive for the exhaust fans is used in conjunction with an electric regulating valve in the fresh air duct to replenish an appropriate amount of cold air, eliminating system heat load and reducing system energy consumption. Simultaneously, differential airflow control ensures stable pressure in the clean area.

Description

Technical Field

[0001] This invention relates to the field of cleanroom air conditioning systems, specifically disclosing a cleanroom air conditioning system and control method with a fresh air natural cooling source. Background Technology

[0002] In the design of cleanroom air conditioning systems, the temperature, humidity, and cleanliness of the return air are typically better than the outdoor air quality. Therefore, maximizing the use of return air, without the risk of cross-contamination, reduces the risk of external environmental contamination while saving energy consumption during summer. Some high-level aseptic production air conditioning systems, with positive pressure leakage to meet personnel fresh air needs, have a fresh air ratio of only 3-5%. While these systems have low cooling demand in summer, they have long cooling cycles due to the inherent temperature rise loads from personnel, lighting, and fans. For projects in northern regions, cleanroom air conditioning systems with low fresh air ratios still require cooling during winter operation.

[0003] Traditional dual-fan air conditioning units use fans connected in series, such as Figure 1 As shown, when partial fresh air is used during the transition season, the fan outlet is under positive pressure and discharged to the atmosphere. At the same time, in order to introduce fresh air, the fresh air section operates under negative pressure. The pressure difference between the return air fan outlet section and the fresh air section is consumed by the connected valve, resulting in energy waste. Summary of the Invention

[0004] To address the aforementioned problems, this invention discloses a purification air conditioning system and control method using a fresh air natural cooling source. The system employs a parallel connection of an exhaust fan and a supply fan. Based on the performance parameters of the exhaust fan, such as air volume and air pressure, a variable frequency drive for the exhaust fan is used in conjunction with an electric regulating valve in the fresh air duct to replenish an appropriate amount of cold air, eliminating system heat load and reducing system energy consumption. Simultaneously, differential airflow control ensures stable pressure in the clean area.

[0005] A cleanroom air conditioning system with a fresh air natural cooling source includes a cleanroom air conditioning unit assembly, an air duct assembly, a water pipe assembly, and a control system. The air duct assembly connects the cleanroom air conditioning unit assembly to the cleanroom, and the water pipe assembly provides refrigerant and heat transfer medium to the cleanroom air conditioning unit assembly. The air duct assembly includes a supply air duct, a return air duct, and a fresh air duct, and an exhaust air duct is provided between the return air duct and the cleanroom air conditioning unit assembly.

[0006] Preferably, the air supply duct, exhaust duct, and fresh air duct are all equipped with air volume detection cylinders and duct regulating valves.

[0007] Preferably, the water pipe assembly includes a temperature control pipe and a humidification pipe, and both the temperature control pipe and the humidification pipe are equipped with a water pipe regulating valve.

[0008] Preferably, the temperature control pipeline includes a refrigeration pipeline and a heating pipeline, and each pipeline is equipped with a regulating valve.

[0009] Preferably, the control system includes a thermometer, a hygrometer, a pressure gauge, and a controller.

[0010] This invention also discloses a control method for a purification air conditioning system with a fresh air natural cooling source, comprising the following steps: Step 1: Divide the control conditions into two parts: temperature and humidity control strategy and pressure control strategy; Step 2: Divide the fresh air control operation into four types of zones: cooling and dehumidification zone, cooling and humidification zone, ratio humidification zone, and ratio heating and humidification zone. Step 3: Based on the outdoor fresh air parameters, determine the operating zone of the air conditioner and activate the corresponding control method.

[0011] Preferably, the operating mode division in step 2 is as follows: (1) Calculate the air temperature and absolute humidity based on the outdoor temperature and humidity design parameters and the indoor temperature and humidity design parameters, and make isotherms and isohumidities; (2) Divide the operating conditions according to the enthalpy-humidity diagram of humid air.

[0012] Preferably, among the four operating zones, the boundary between the cooling and dehumidification zone and the cooling and humidification zone is d=9.1g / kg, the boundary between the cooling and humidification zone and the adjustable humidification zone is t=13℃, and the boundary between the adjustable humidification zone and the constant ratio heating and humidification zone is t=-8℃.

[0013] Preferably, in step 2, the fresh air section uses the dry-bulb temperature and relative humidity of the air to calculate the saturated vapor pressure of the humid air according to the formula.

[0014] Preferably, the outdoor fresh air parameters in step 3 are ambient temperature and relative humidity. Preferably, in step 3, the control method is as follows: Mode 1: When the fresh air detection parameters are calculated and located in the cooling and dehumidification zone, the return air temperature and humidity are the main control parameters, with humidity control taking priority. The water pipe cooling regulating valve is adjusted for the first time, and then the supply air temperature and humidity are the secondary control parameters, and the water pipe cooling regulating valve is adjusted for the second time. Mode 2: When the fresh air detection parameters are calculated and located in the cooling and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe cooling regulating valve is adjusted for the first time, and the temperature after the surface cooler is controlled at the boundary between the cooling and humidification zone and the ratio humidification zone. The water pipe humidification regulating valve is adjusted for the first time, and the supply air temperature and humidity are the secondary control parameters. At the same time, the water pipe cooling regulating valve and the water pipe humidification regulating valve are adjusted for the second time.

[0015] Mode 3: When the fresh air detection parameters are calculated and located in the proportional humidification zone, the outdoor fresh air temperature and humidity are the main control parameters. After calculation, the exhaust fan speed is adjusted so that the measured value of the exhaust air volume detection tube meets the proportional adjustment requirements. The water pipe humidification regulating valve is adjusted for the first time, and the supply air temperature and humidity are the secondary control parameters. The water pipe humidification regulating valve is adjusted for the second time.

[0016] Mode 4: When the fresh air detection parameters are calculated and located in the constant ratio heating and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe heating regulating valve is adjusted for the first time, and the water pipe humidification regulating valve is adjusted for the first time as well. The supply air temperature and humidity are the secondary control parameters, and the water pipe heating regulating valve and the water pipe humidification regulating valve are adjusted for the second time.

[0017] Preferably, the pressure control strategy in step 1 is as follows: The essence of cleanroom differential pressure control is differential air volume control, that is, fresh air volume = exhaust air volume + differential pressure air volume. The system adopts active pressure control, with differential pressure air volume as the main control parameter, adjusting the differential air volume regulating valve of the fresh air duct, and the cleanroom pressure as the auxiliary control parameter, adjusting the air volume regulating valve.

[0018] Beneficial effects: 1. The control zone is expanded to include a ratio humidification zone. During the transitional season, the system switches to ratio humidification mode based on the outdoor air conditioning parameters. When the outdoor temperature is the primary control parameter, the fan speed is controlled to ensure that the exhaust air reaches the calculated rated air volume. When the indoor temperature and humidity are the primary control parameters, the system controls the humidification capacity and performs combined regulation of the air and water systems in the ratio humidification zone.

[0019] 2. The system's pressure control strategy adopts active pressure control, with the difference between fresh air volume and exhaust air volume as the main control parameter and the cleanroom pressure as the auxiliary control parameter. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a structural schematic diagram in the background art of this invention; Figure 2 This is a schematic diagram of the technical solution of the present invention; Figure 3 This is a flowchart of the control process of the present invention; Figure 4 It is an enthalpy-humidity map showing the regional divisions. Detailed Implementation Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] like Figure 2-4 As shown, this invention discloses a purification air conditioning system and control method using a fresh air natural cooling source. The system recycles and reuses the return air from the cleanroom, employing a parallel connection of exhaust and supply fans. During transitional seasons and winter, the system uses a frequency converter on the exhaust fan and an electric regulating valve in the fresh air duct to inject an appropriate amount of cold air into the supply air duct, eliminating the room's heat load and reducing system energy consumption. Simultaneously, differential airflow control ensures stable pressure in the clean area.

[0023] The system includes a clean air conditioning unit assembly, air duct assembly, water pipe assembly, and a control system. The control system includes instruments and controllers, and the instruments include thermometers, hygrometers, pressure gauges, etc.

[0024] The cleanroom air conditioning unit assembly includes, sequentially arranged along the airflow direction, an exhaust fan section, a fresh air section, a primary filter section, a return air section, a surface cooling water baffle section, a supply fan section, a flow equalization section, a heating section, a humidification section, a medium-efficiency filter section, and an outlet air section. The supply air duct connects the outlet air section of the air conditioning system to the cleanroom. The cleanroom's return air vent is connected back to the air conditioning system via a return air duct, providing circulating air to the cleanroom. The return air duct has three branches: a primary return air duct, a secondary return air duct, and an exhaust air duct. A portion of the return air is transported to the air conditioning system's return air section via the primary return air duct, a portion is transported to the supply fan section via the secondary return air duct, and the remaining portion is transported to the exhaust fan section via the exhaust air duct and discharged to the outside by the exhaust fan. Outside fresh air is transported to the fresh air section via the fresh air duct and, together with the primary and secondary return air, is transported to the cleanroom via the supply air duct. The supply air duct, exhaust air duct, and fresh air duct are all equipped with air volume detection cylinders. The supply air duct, exhaust air duct, fresh air duct, primary return air duct, and secondary return air duct are all equipped with duct regulating valves. These duct regulating valves are connected to the controller, and the controller's control signals are used to control each duct.

[0025] The exhaust fan is a variable frequency fan, and its air volume is 30% of the system's calculated air volume, for the following reasons: 1) The disinfection and exhaust ventilation standards for Grade B areas require that the air supply volume be more than 30%.

[0026] 2) The minimum air volume of the variable frequency fan is usually 1 / 3 of the design air volume, that is, 10% of the system air volume.

[0027] 3) Calculations show that 30% is the control zone boundary, especially the boundary between the cooling and humidification zone and the ratio humidification zone, which is t=13℃ and is suitable for the operation of the chiller unit.

[0028] Among them, the cooling section, heating section, and humidification section are the temperature and humidity control functional sections of the air purification unit.

[0029] The water piping assembly includes temperature control piping and humidification piping. The temperature control piping includes cooling piping and heating piping. The cooling piping provides 7-12 degree Celsius chilled water to the surface cooling water baffle section for cooling the system's return air. The heating piping provides 0.3 MPa steam to the heating section for heating the system in extreme weather conditions where outdoor temperatures drop below -8 degrees Celsius. The humidification piping provides 0.3 MPa steam to the humidification section to ensure suitable humidity in the supply air ducts. Both the temperature control and humidification piping are equipped with water pipe regulating valves, which are connected to the controller. The controller's control signals control the water pipes.

[0030] The method for controlling this system using a controller is as follows: 1. Based on the outdoor and indoor temperature and humidity design parameters, using isotherms and isohumidities, and according to the enthalpy-humidity diagram of humid air, the system is divided into four operating zones: Zone 1 (cooling and dehumidification zone), Zone 2 (cooling and humidification zone), Zone 3 (adjustment humidification zone), and Zone 4 (constant ratio heating and humidification zone).

[0031] The boundary between Zone 1 and Zone 2 is d=9.1g / kg, the boundary between Zone 2 and Zone 3 is t=13℃, and the boundary between Zone 3 and Zone 4 is t=-8℃.

[0032] 2. Controller Calculation Method: The dry-bulb temperature t and relative humidity ψ of the fresh air section are measured by temperature and humidity sensors. The saturated vapor pressure of the moist air is calculated according to the following formula. , When t=200℃; In the formula; c8 = -5800.2206; c9 = 1.3914993; c 10 =-0.04860239; c 11 =0.41764768×10 -4 ; c 12 =-0.14452093×10 -7 c 13 =6.5459673.

[0033] Calculate the air humidity d using the following formula, where B is atmospheric pressure. The relative humidity being measured.

[0034] 3. Based on the temperature t and the humidity d, determine the operating zone of the air conditioner and activate the corresponding control method.

[0035] 4. The following is a table of the operation combinations for zoned control methods and control instruments. a. Temperature and humidity control strategies: Mode 1: When the fresh air detection parameters are calculated and located in Zone 1 (cooling and dehumidification zone), the return air temperature and humidity are the main control parameters, with humidity control taking priority. The water pipe cooling regulating valve is adjusted for the first time, and then the supply air temperature and humidity are adjusted for the second time.

[0036] Mode 2: When the fresh air detection parameters are calculated and located in the cooling and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe cooling regulating valve is adjusted for the first time, and the temperature after the surface cooler is controlled at the boundary between the cooling and humidification zone and the ratio humidification zone. The water pipe humidification regulating valve is adjusted for the first time, and the supply air temperature and humidity are the secondary control parameters. At the same time, the water pipe cooling regulating valve and the water pipe humidification regulating valve are adjusted for the second time.

[0037] Mode 3: When the fresh air detection parameters are calculated and located in the proportional humidification zone, the outdoor fresh air temperature and humidity are the main control parameters. After calculation, the exhaust fan speed is adjusted so that the measured value of the exhaust air volume detection tube meets the proportional adjustment requirements. The water pipe humidification regulating valve is adjusted for the first time, and the supply air temperature and humidity are the secondary control parameters. The water pipe humidification regulating valve is adjusted for the second time.

[0038] Mode 4: When the fresh air detection parameters are calculated and located in the constant ratio heating and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe heating regulating valve is adjusted for the first time, and the water pipe humidification regulating valve is adjusted for the first time as well. The supply air temperature and humidity are the secondary control parameters, and the water pipe heating regulating valve and the water pipe humidification regulating valve are adjusted for the second time.

[0039] b. Stress control strategies: The essence of cleanroom differential pressure control is differential air volume control, that is, fresh air volume = exhaust air volume + differential pressure air volume. The system adopts active pressure control, with differential pressure air volume as the main control parameter, adjusting the differential air volume regulating valve of the fresh air duct, and the cleanroom pressure as the auxiliary control parameter, adjusting the air volume regulating valve.

[0040] The technical effects of this application are illustrated below using a technical upgrade project of a freeze-dried powder injection workshop in a certain region as an example: I. Project Overview The building area to be renovated is 1645m2, and the fire resistance rating is Class II. The left side of the workshop is the production auxiliary area, including rooms such as refrigeration room, air compressor room, water treatment room, and power distribution room. The right side of the workshop is the clean production area, including functional rooms for bottle washing and stopper washing, weighing, liquid preparation, pre-sterilization room, post-sterilization room, freeze-drying room, capping room, automatic light inspection, and packaging room.

[0041] II. Design Parameters 1. Obtain outdoor meteorological data for the area. (1) Atmospheric pressure: 101.91 kPa in winter; 99.79 kPa in summer.

[0042] (2) Calculated outdoor dry bulb temperature for air conditioning: -7.7℃ in winter; 34.7℃ in summer.

[0043] (3) The calculated outdoor wet-bulb temperature of the air conditioner in summer is 26.8℃.

[0044] (4) The outdoor calculated relative humidity of the air conditioner in winter (the average outdoor calculated relative humidity of the coldest month) is 53%. 2. Core clean area, including sterilization post-sterilization room, freeze-drying pre-sterilization room, etc., is classified as Class B. Room design parameters: 22±2℃, 45~60%, and static pressure difference between clean room and non-clean room is greater than or equal to 10Pa.

[0045] III. Design Scheme 1. The air conditioning system is a centralized, all-air system. The air in the clean area is filtered through primary, medium, and high-efficiency filters before being delivered indoors.

[0046] 2. According to the specifications, the air exchange rate of a Class B cleanroom is greater than 60 times / hour, and the system is designed to supply air volume of 24,000 m3 / h. Class B cleanrooms use fumigation sterilization, and residual gases are promptly removed after disinfection. A disinfection exhaust fan is installed, with an air volume of 30% of the total air volume. The system is designed to supply disinfection exhaust air volume of 7,200 m3 / h.

[0047] 3. The refrigerant for the workshop's modular air conditioning system is 7 / 12°C chilled water, and a water-cooled screw chiller unit is selected. The heating medium is steam (0.3MPa), and the air conditioning humidification is steam humidification, with the steam sourced from the external pipeline network.

[0048] IV. Designed according to the traditional dual-fan series design mode 1. Parameters of return air fan and supply air fan: Return air fan design parameters: air volume 24000m3 / h, total pressure 750Pa, power 11kW; supply air fan design parameters: air volume 24000m3 / h, total pressure 1550Pa, power 18.5kW. 2. Operating Mode The exhaust outlet regulating valve of the air conditioning unit adjusts the exhaust volume to 10% of the system air volume, i.e., 2400 m3 / h. At the same time, outdoor fresh air is introduced into the air conditioning unit to maintain a positive pressure of more than 10 Pa in the clean room.

[0049] 3. Energy Consumption Analysis 3.1 Fan energy consumption According to Section 9.2.15 of GB50457 "Design Standard for Cleanrooms in Pharmaceutical Industry", the air conditioning system of the clean area for sterile drug production should operate continuously to maintain the corresponding cleanliness level.

[0050] Wind turbine energy consumption: (11 + 18.5) * 24 * 365 = 258420 kWh 3.2 Operating energy consumption of air conditioning refrigeration systems 3.2.1 Calculation Conditions The innovation of this patent lies in the ratio humidification zone, therefore only the operating energy consumption of air conditioning refrigeration in the ratio humidification zone is calculated.

[0051] According to Appendix A of the "Code for Design of Heating, Ventilation and Air Conditioning of Industrial Buildings" GB50019, the number of days with an average daily temperature ≤8℃ in this area is 122.

[0052] According to relevant data, the inherent heat load per unit area of ​​a cleanroom is 15 W / m² for personnel, 25 W / m² for lighting, and 110 W / m² for fan temperature rise. The area of ​​the Class B cleanroom in this project is 150 m². The inherent heat load of the Class B cleanroom air conditioning system is: (15 + 25 + 110) * 150 = 22.5 kW Overall energy efficiency ratio of the refrigeration system: ξ=3.5 As the outdoor temperature gradually decreases, the overall temperature difference coefficient is 0.5. 3.2.2 Operating energy consumption of the air conditioning refrigeration system in the ratio-controlled humidification zone. 22.5 * 0.5 * 24 * 122 / 3.5 = 9411 kWh V. Design of Purification Air Conditioning and Control System for Fresh Air Natural Cooling Source 1. Parameters of exhaust fan and supply fan: Exhaust fan design parameters: air volume 7200 m3 / h, total pressure 750 Pa, power 4 kW; supply fan design parameters: air volume 24000 m3 / h, total pressure 1950 Pa, power 22 kW. 2. Division of Operating Zones Based on the cleanroom interior design parameters of 22℃, 55% humidity, and 9.1g / kg absolute humidity, the boundary between Zone 1 and Zone 2 is set at d=9.1g / kg. According to the inherent heat load calculation of the Class B zone air conditioning system, the boundary between Zone 2 and Zone 3 is set at t=13℃, and the boundary between Zone 3 and Zone 4 is set at t=-8℃. 3. Energy Consumption Analysis 3.1 Wind turbine energy consumption: (22+4)*24*365=227760kWh 3.2 Operating energy consumption of air conditioning refrigeration systems In the humidification zone, this solution uses outdoor fresh air as the cold source, and the air conditioning refrigeration system is turned off.

[0053] VI. Economic Benefits and Carbon Dioxide Emission Reduction The cost savings over one operating year are calculated based on an electricity cost of 0.8 yuan / kWh. (258420-227760+9411)*0.8=32056 (yuan) Operating carbon emission reduction accounting The average CO2 emission factor (kGCO2 / kWh) of the power grid in North China is 0.8843. The reduction in CO2 emissions from electricity consumption is: (258420-227760+9411)*0.8843=35434 (kGCO2). The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a purified air conditioning system with a fresh air natural cooling source, characterized in that, The system includes a cleanroom air conditioning unit assembly, a ductwork assembly, a water pipe assembly, and a control system. The ductwork assembly connects the cleanroom air conditioning unit assembly to the cleanroom, and the water pipe assembly provides refrigerant and heat transfer medium to the cleanroom air conditioning unit assembly. The ductwork assembly includes a supply air duct, a return air duct, and a fresh air duct. An exhaust air duct is provided between the return air duct and the cleanroom air conditioning unit assembly. The air supply duct, exhaust duct, and fresh air duct are all equipped with air volume detection cylinders and duct regulating valves; The water pipe assembly includes a temperature control pipe and a humidification pipe, both of which are equipped with water pipe regulating valves; The temperature control pipeline includes a refrigeration pipeline and a heating pipeline, and each pipeline is equipped with a regulating valve; The control system includes a thermometer, a hygrometer, a pressure gauge, and a controller; The control method includes the following steps: Step 1: Divide the control conditions into two parts: temperature and humidity control strategy and pressure control strategy; The essence of cleanroom differential pressure control is differential air volume control, that is, fresh air volume = exhaust air volume + differential pressure air volume. The system adopts active pressure control, with differential pressure air volume as the main control parameter, which adjusts the differential air volume regulating valve of the fresh air duct, and the cleanroom pressure as the auxiliary control parameter, which adjusts the air volume regulating valve. Step 2: Divide the fresh air control operation into four types of operation zones: cooling and dehumidification zone, cooling and humidification zone, ratio-adjusted humidification zone, and ratio-heated humidification zone; The operating modes are divided as follows: (1) Calculate the air temperature and absolute humidity based on the outdoor temperature and humidity design parameters and the indoor temperature and humidity design parameters, and make isotherms and isohumidities; (2) Divide the operating conditions according to the enthalpy-humidity diagram of humid air; The boundary between the cooling and dehumidification zone and the cooling and humidification zone is d=9.1g / kg; the boundary between the cooling and humidification zone and the ratio-adjusting humidification zone is t=13℃; and the boundary between the ratio-adjusting humidification zone and the ratio-heating humidification zone is t=-8℃. Step 3: Based on the ambient temperature and relative humidity of the outdoor fresh air, determine the operating zone of the air conditioner and activate the control method of the following mode; Mode 1: When the fresh air detection parameters are calculated and located in the cooling and dehumidification zone, the return air temperature and humidity are the main control parameters, with humidity control taking priority. The water pipe cooling regulating valve is adjusted for the first time, and then the supply air temperature and humidity are the secondary control parameters, and the water pipe cooling regulating valve is adjusted for the second time. Mode 2: When the fresh air detection parameters are calculated and located in the cooling and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe cooling regulating valve is adjusted for the first time. The temperature after the surface cooler is controlled at the boundary between the cooling and humidification zone and the ratio humidification zone. The water pipe humidification regulating valve is adjusted for the first time. The supply air temperature and humidity are the secondary control parameters. At the same time, the water pipe cooling regulating valve and the water pipe humidification regulating valve are adjusted for the second time. Mode 3: When the fresh air detection parameters are calculated and located in the proportional humidification zone, the outdoor fresh air temperature and humidity are the main control parameters. After calculation, the exhaust fan speed is adjusted so that the measured value of the exhaust air volume detection tube meets the proportional adjustment requirements. The water pipe humidification regulating valve is adjusted for the first time, with the supply air temperature and humidity as the secondary control parameters. The water pipe humidification regulating valve is adjusted for the second time. Mode 4: When the fresh air detection parameters are calculated and located in the constant ratio heating and humidification zone, the return air temperature and humidity are the main control parameters. The water pipe heating regulating valve is adjusted for the first time, and the water pipe humidification regulating valve is adjusted for the first time as well. The supply air temperature and humidity are the secondary control parameters, and the water pipe heating regulating valve and the water pipe humidification regulating valve are adjusted for the second time.

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