A control method and system for a direct expansion evaporator

Abstract

This invention discloses a control method and system for a direct expansion evaporator. The system includes an air handling module, a sensing module, a logic control module, and a compressor drive module connected in sequence. The air handling module is a fresh air handling unit, which has a fresh air section, a pre-filter section, a pre-stage direct expansion section, a post-stage direct expansion section, and a supply air section arranged sequentially along the fresh air flow direction. This invention employs a two-stage direct expansion section structure, coupled with precise monitoring by an evaporation temperature sensor, avoiding the heat exchange imbalance problem of a single-stage coil. The logic control module operates in stages according to the fresh air temperature; at low temperatures, only the post-stage is activated, preventing icing and ensuring continuous operation, thus improving energy efficiency. Furthermore, through multi-dimensional sensor data, the logic control module dynamically adjusts the compressor status, activating it according to room temperature and humidity deviations, with coordinated adjustment between the pre- and post-stages. When the post-stage temperature is too low, the pre-stage temperature is gradually reduced, avoiding temperature fluctuations caused by traditional shutdowns, achieving precise temperature control, reducing equipment wear, and extending lifespan.

Description

Technical Field

[0001] This invention belongs to the field of evaporator control technology, and particularly relates to a control method and system for a direct expansion evaporator. Background Technology

[0002] In direct expansion air conditioners, the operating status of the evaporator is crucial to the cooling effect and equipment reliability. Large direct expansion units using single-stage large coils are prone to heat exchange imbalance and coil icing due to uneven air distribution. While two-stage or multi-stage coils can improve this, when the fresh air temperature is low and indoor cooling is required, the air temperature is further reduced after pre-cooling by the upstream evaporator coil, leading to a sharp drop in the heat exchange efficiency of the downstream evaporator and making it extremely prone to icing, which seriously affects the operation of the unit. Traditional systems lack a coordinated strategy for driving the compressors of the upstream and downstream coils. When the operation of the upstream coil causes the downstream temperature to drop too low, the load cannot be adjusted by gradually reducing the number of upstream coils in operation. Instead, a single shutdown protection mechanism is required, which affects both the indoor cooling effect and the continuity of equipment operation. In view of the above reasons, this application proposes a control method and system for a direct expansion evaporator. Summary of the Invention

[0003] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a control method and system for a direct expansion evaporator.

[0004] Technical solution To achieve the above objectives, the present invention provides the following technical solution: a control system for a direct expansion evaporator. The system includes an air handling module, a sensor detection module, a logic control module, and a compressor drive module connected in sequence. The air handling module is a fresh air unit. The fresh air unit is equipped with a fresh air section, a primary filter section, a pre-stage direct expansion section, a post-stage direct expansion section and a supply air section in sequence along the fresh air flow direction. After the fresh air enters the unit, it passes through the pre-stage direct expansion section for pre-cooling and the post-stage direct expansion section for re-cooling. The sensing module is used to collect temperature and humidity information; The logic control module generates control commands based on the information from the sensor detection module; The compressor drive module controls the operation of the compressor in the front and rear direct expansion stages according to control commands; The logic control module has a built-in linkage control unit. After both the compressor systems of the current stage and the subsequent stage direct expansion stage are started, if the evaporator coil temperature of any subsequent stage direct expansion stage compressor system is ≤T2 and the running time reaches a preset threshold, the linkage control unit sends a load reduction command to the compressor drive module, controlling the number of compressor systems in the current stage direct expansion stage to decrease by 1. After a set time, if the evaporator coil temperature of any subsequent stage direct expansion stage compressor system is again detected to be ≤T2, the load reduction command is sent repeatedly until the evaporator coil temperature of the subsequent stage direct expansion stage compressor system is >T2. If the evaporator coil temperature of the subsequent stage direct expansion stage compressor system still does not rise, the linkage control unit sends a shutdown command to the compressor drive module, stopping the compressor of the corresponding system in the subsequent stage direct expansion stage whose evaporator coil temperature is ≤T2.

[0005] Preferably, in the air handling module, each system of each coil in the pre-stage direct expansion section and the post-stage direct expansion section is equipped with an evaporation temperature sensor. The evaporation temperature sensor is installed on the distribution pipe of the system and is used to collect the temperature at the lowest point of the system temperature. The sensing and detection module integrates the detection data of the evaporation temperature sensor to participate in the system control. The sensing and detection module also includes a fresh air temperature sensor and a room temperature and humidity sensor; the fresh air temperature sensor is used to acquire the fresh air temperature Tfresh air, and the room temperature and humidity sensor is used to acquire the room temperature Troom and the room humidity Hroom; the logic control module receives and stores the above temperature and humidity data.

[0006] Preferably, in cooling mode, the logic control module generates a compressor start command by comparing the room temperature T_room with the target temperature TSet and the room humidity H_room with the target humidity HSet. If T_room ≥ TSet + T_deviation and H_room ≥ HSet + H_deviation, the logic control module sends a start command to the compressor drive module to control the unit's compressor system to start.

[0007] Preferably, the logic control module has a built-in fresh air temperature judgment unit; when the fresh air temperature Tfresh air ≤ the set temperature T1 and the duration reaches a preset threshold, the fresh air temperature judgment unit sends a restriction command to the compressor drive module to prohibit the start of the compressor system related to the front-stage direct expansion section, and only allows the compressor drive module to run the compressor of the compressor system related to the rear-stage direct expansion section. When the current direct expansion compressor is prohibited from starting, the compressor drive module starts the subsequent direct expansion compressor system. After the system has been running for a specified time, the logic control module obtains the value of the evaporation temperature sensor of the subsequent direct expansion section. When the evaporation temperature sensor value of any subsequent system is lower than the set temperature T2 and the duration reaches the preset threshold, a shutdown command is sent to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value of the system recovers, a restart command is sent to restart the compressor of the system.

[0008] Preferably, when the fresh air temperature judgment unit of the logic control module is such that the fresh air temperature Tfresh air ≥ T1 and the duration reaches a preset threshold, and the startup conditions are met and there are no alarms in any system, the compressor drive module sends a graded startup command to the compressor drive module. The compressor drive module starts the three compressor systems of the downstream direct expansion section sequentially according to a preset time. When the downstream compressor is running at full capacity and the coil temperature of the downstream direct expansion section is not lower than T2, the compressor drive module starts the three compressor systems of the upstream direct expansion section sequentially according to a set time Time1. During the startup process, if the coil temperature of any downstream direct expansion section is lower than T2, the logic control module sends an adjustment command to the compressor drive module to control the three compressor systems of the upstream direct expansion section to pause loading and switch to unloading. After the compressor in the front-stage direct expansion section starts and the running time reaches a preset threshold, the logic control module obtains the value of the evaporation temperature sensor in the front-stage direct expansion section. When the evaporation temperature sensor value of any system in the front stage is lower than T2 and the running time reaches a preset threshold, the logic control module sends a stop command to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value of the system recovers, the logic control module sends a restart command to restart the compressor of the system.

[0009] This invention also proposes a control method for a direct expansion evaporator, the method comprising the following steps: Step 1: System Initialization: Start the air handling module, sensor detection module, logic control module and compressor drive module, complete self-test and establish connection, and each module enters the standby state; Step 2, Information Acquisition: The sensing and detection module collects data such as the evaporation temperature, fresh air temperature, and room temperature and humidity of the front and rear direct expansion sections, and transmits them to the logic control module for storage; Step 3, Cooling Start Judgment: Based on the data from the sensor detection module, when the room temperature and humidity reach the start-up conditions, the logic control module sends a command to the compressor drive module to start the unit compressor. Step 4, Fresh Air Temperature Control: The logic control module determines the fresh air temperature. If it is lower than T1 and continues to reach the threshold, it instructs the compressor drive module to run only the downstream direct expansion compressor. Step 5, Post-stage operation control: After the post-stage starts, the logic control module, based on the data from the sensor detection module, if the post-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop the corresponding system, and restarts after recovery; Step 6: Pre-stage staged start-up: When the fresh air temperature meets the standard and conditions are met, the logic control module instructs the compressor drive module to start the three downstream compressors first. After the downstream compressors are normal, the upstream compressors will start. If the downstream compressor temperature is too low during startup, the upstream compressors will pause loading and reduce load. Step 7, Pre-stage Operation Control: After the pre-stage starts, the logic control module, based on the data from the sensor detection module, if the pre-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop, and restarts after recovery; Step 8, Linkage Control: When both the front and rear stages are turned on, the logic control module, based on the data from the sensor detection module, will gradually reduce the number of front stages if the temperature of the rear stage is too low and continues to reach the threshold; if this is still ineffective, the corresponding system of the rear stage will be stopped.

[0010] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention adopts a two-stage processing structure of pre-cooling in the front-stage direct expansion section and re-cooling in the rear-stage direct expansion section. Combined with the precise monitoring of the lowest temperature point of the system by the evaporation temperature sensor, it can effectively avoid the heat exchange imbalance problem caused by uneven air distribution in traditional single-stage large coil tubes. At the same time, the logic control module realizes a graded operation strategy through the fresh air temperature judgment unit. When the fresh air temperature is low, only the rear-stage direct expansion section is activated, which can prevent the risk of icing in the rear stage caused by excessive pre-cooling in the front stage. This ensures continuous operation of the equipment and improves the energy utilization efficiency of the refrigeration process. 2. This invention utilizes multi-dimensional data acquisition from room temperature and humidity sensors and fresh air temperature sensors. The logic control module can dynamically adjust the compressor's operating status based on actual environmental parameters. In cooling mode, the start-up timing is determined by the deviation between room temperature and humidity and target values. Combined with a linkage control strategy—if the temperature of the downstream stage is too low when the upstream stage is running simultaneously, the number of upstream stages running is gradually reduced, avoiding temperature fluctuations caused by traditional single shutdown protection. This graded start-up and linkage adjustment method not only meets the precise control requirements of indoor temperature and humidity but also reduces the losses from frequent start-ups and shutdowns of the equipment, extending the unit's service life.

[0011] 3. In summary, this invention adopts a two-stage direct expansion section structure, combined with precise monitoring by an evaporation temperature sensor, to avoid the problem of heat exchange imbalance in single-stage coils; the logic control module operates in stages according to the fresh air temperature, only activating the downstream stage when the temperature is low, preventing icing and ensuring continuous operation, thus improving energy efficiency; furthermore, through multi-dimensional sensor data, the logic control module dynamically adjusts the compressor status, activating according to the room temperature and humidity deviation, with coordinated adjustment between upstream and downstream stages, gradually reducing the upstream stage temperature when the downstream stage temperature is too low, avoiding temperature fluctuations caused by traditional shutdowns, achieving precise temperature control, reducing equipment wear, and extending lifespan. Attached Figure Description

[0012] Figure 1 This is a system block diagram of the present invention; Figure 2 This is a flowchart illustrating the overall process of the method of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] like Figure 1-2 As shown, an embodiment of the present invention provides a control system for a direct expansion evaporator, comprising an air handling module, a sensing and detection module, a logic control module, and a compressor drive module connected in sequence; In the air handling module, each coil of the pre-stage direct expansion section and the post-stage direct expansion section is equipped with an evaporation temperature sensor. The evaporation temperature sensor is installed on the distribution pipe of the system and is used to collect the temperature at the lowest point of the system. The air handling module is a fresh air handling unit. The fresh air handling unit is provided with a fresh air section, a primary filter section, a pre-stage direct expansion section, a post-stage direct expansion section and a supply air section in sequence along the fresh air flow direction. After the fresh air enters the unit, it passes through the pre-stage direct expansion section for pre-cooling and the post-stage direct expansion section for re-cooling in sequence. The sensing and detection module is used to collect temperature and humidity information. The sensing and detection module integrates the detection data of the evaporation temperature sensor to participate in system control. The sensing and detection module also includes a fresh air temperature sensor and a room temperature and humidity sensor. The fresh air temperature sensor is used to obtain the fresh air temperature T. 新风 The room temperature and humidity sensor is used to obtain the room temperature T. 房间 and room humidity H 房间 ; The logic control module receives and stores the above temperature and humidity data; The logic control module generates control commands based on information from the sensor detection module. In cooling mode, the logic control module compares the room temperature T... 房间 With target temperature T Set Compare room humidity H 房间 With target humidity H Set Generates a compressor start command; If: T 房间 ≥T Set +T 偏差 H 房间 ≥H Set +H偏差 ; The logic control module sends a start command to the compressor drive module to control the unit's compressor system to start. The logic control module has a built-in fresh air temperature judgment unit. Fresh air temperature T 新风 ≤T1, where: T1 is the set temperature; When the fresh air temperature T 新风 If the temperature is ≤T1 and the duration reaches a preset threshold, the fresh air temperature judgment unit sends a restriction command to the compressor drive module to prohibit the start of the compressor system related to the front-stage direct expansion section and only allow the compressor drive module to run the compressor of the compressor system related to the rear-stage direct expansion section. When the compressor of the front-stage direct expansion section is prohibited from starting, the compressor drive module starts the compressor system of the rear-stage direct expansion section. The logic control module acquires the value of the evaporation temperature sensor in the downstream direct expansion section after the system has been running for a specified time. When the evaporation temperature sensor value of any downstream system is lower than T2 and the duration reaches a preset threshold, a shutdown command is sent to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value recovers, a restart command is sent to restart the compressor of the system. Where: T2 is the set temperature; The fresh air temperature judgment unit of the logic control module is located at a fresh air temperature T. 新风 When the duration of the signal reaches or exceeds T1 and the preset threshold is met, and the startup conditions are satisfied and there are no alarms in any system, a graded startup command is sent to the compressor drive module. The compressor drive module starts the three compressor systems of the downstream direct expansion section in sequence according to a preset time. When the downstream compressor is running at full capacity and the temperature of the downstream direct expansion section coil is not lower than T2, the compressor drive module operates according to a set time T. ime1 The three compressor systems in the front direct expansion section are started sequentially; During startup, if the temperature of any downstream direct expansion section coil is lower than T2, the logic control module sends an adjustment command to the compressor drive module to control the three compressor systems of the upstream direct expansion section to suspend loading and switch to unloading. The logic control module acquires the value of the evaporation temperature sensor of the front-stage direct expansion section after the compressor in the front-stage direct expansion section starts and the running time reaches a preset threshold. If the evaporation temperature sensor value of any system in the current stage is lower than T2 and the running time reaches a preset threshold, the logic control module sends a stop command to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value of the system recovers, a restart command is sent to restart the compressor of the system. The logic control module has a built-in linkage control unit. After both the compressor systems of the current stage direct expansion section and the subsequent stage direct expansion section are turned on, if the evaporator coil temperature of any subsequent stage direct expansion section compressor system is ≤T2 and the running time reaches a preset threshold, the linkage control unit sends a load reduction command to the compressor drive module to control the number of the current stage direct expansion section compressor system to decrease by 1. If, after a set time, the evaporator coil temperature of any downstream direct expansion compressor system is again detected to be ≤T2, the load reduction command is repeatedly sent until the evaporator coil temperature of the downstream direct expansion compressor system is >T2. If the evaporator coil temperature of the downstream direct expansion section compressor system still does not rise, the linkage control unit sends a shutdown command to the compressor drive module to stop the compressor of the corresponding system in the downstream direct expansion section where the evaporator coil temperature is ≤T2. The compressor drive module controls the operation of the compressor in the front and rear direct expansion stages according to control commands.

[0015] This invention also proposes a control method for a direct expansion evaporator, the method comprising the following steps: Step 1: System Initialization: Start the air handling module, sensor detection module, logic control module and compressor drive module, complete self-test and establish connection, and each module enters the standby state; Step 2, Information Acquisition: The sensing and detection module collects data such as the evaporation temperature, fresh air temperature, and room temperature and humidity of the front and rear direct expansion sections, and transmits them to the logic control module for storage; Step 3, Cooling Start Judgment: Based on the data from the sensor detection module, when the room temperature and humidity reach the start-up conditions, the logic control module sends a command to the compressor drive module to start the unit compressor. Step 4, Fresh Air Temperature Control: The logic control module determines the fresh air temperature. If it is lower than T1 and continues to reach the threshold, it instructs the compressor drive module to run only the downstream direct expansion compressor. Step 5, Post-stage operation control: After the post-stage starts, the logic control module, based on the data from the sensor detection module, if the post-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop the corresponding system, and restarts after recovery; Step 6: Pre-stage staged start-up: When the fresh air temperature meets the standard and conditions are met, the logic control module instructs the compressor drive module to start the three downstream compressors first. After the downstream compressors are normal, the upstream compressors will start. If the downstream compressor temperature is too low during startup, the upstream compressors will pause loading and reduce load. Step 7, Pre-stage Operation Control: After the pre-stage starts, the logic control module, based on the data from the sensor detection module, if the pre-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop, and restarts after recovery; Step 8, Linkage Control: When both the front and rear stages are turned on, the logic control module, based on the data from the sensor detection module, will gradually reduce the number of front stages if the temperature of the rear stage is too low and continues to reach the threshold; if this is still ineffective, the corresponding system of the rear stage will be stopped.

[0016] In practical application, the operation of a single dual-evaporator coil direct expansion unit follows the following process: it is configured with 6 systems and 6 compressors, the pre-stage evaporator contains 3 systems and 3 compressors, the post-stage evaporator contains 3 systems and 3 compressors, each evaporator coil is equipped with 3 temperature sensors, and the pre-stage and post-stage evaporators are placed one after the other. After the unit is started, the room temperature and humidity are checked first. When the room temperature T... 房间 ≥Target Temperature T Set With T 偏差 The sum of, or room humidity H 房间 ≥Target Humidity H Set With H 偏差 The sum of these conditions determines whether there is a need to turn on the compressor, provided that one of these conditions is met. If the fresh air temperature T is detected at this time 新风 At temperatures below 10.0℃, the three compressors in the pre-stage system are not allowed to start. The three compressors in the post-stage system will start sequentially according to the principle of balanced wear, provided there are no alarms. During operation, if the coil temperature of any post-stage system drops below -1.0℃, the compressor in that system will immediately stop running. When the room temperature and humidity reach the required levels, the post-stage compressors will stop sequentially according to the order in which they started. The system will then determine whether to restart the compressors based on changes in room temperature. When the fresh air temperature T 新风 When the temperature is ≥10.0℃, the compressors in the pre-stage system are allowed to start. The starting sequence is also the same: first turn on the three compressors in the post-stage system, starting them sequentially according to the principle of balanced wear. After all the compressors in the post-stage system are turned on, if there is still a cooling demand indoors, turn on the three compressors in the pre-stage system sequentially according to the principle of balanced wear; if there is no longer a cooling demand indoors, keep the number of compressors currently turned on unchanged. When the room temperature and humidity reach the required level, first turn off the compressors in the pre-stage system sequentially, then turn off the compressors in the post-stage system according to the actual temperature demand. The system will also determine whether to restart the compressors based on the room temperature conditions afterward. When the upstream and downstream systems are running simultaneously, if the temperature of any coil in the downstream system is below -1.0°C, the number of compressors running in the upstream system is reduced by one. After a period of time, the temperature is checked again. If the temperature of any coil in the downstream system is still below -1.0°C, the number of compressors running in the upstream system is further reduced. This cycle continues until the temperature of all evaporator coils in the downstream system is above -1.0°C. If all compressors in the upstream system are shut down, but the temperature of any coil in the downstream system is still below -1.0°C, then the compressor in that downstream system is shut down. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control system for a direct expansion evaporator, characterized by, The system includes an air handling module, a sensor detection module, a logic control module, and a compressor drive module connected in sequence. The air handling module is a fresh air unit. The fresh air unit is equipped with a fresh air section, a primary filter section, a pre-stage direct expansion section, a post-stage direct expansion section and a supply air section in sequence along the fresh air flow direction. After the fresh air enters the unit, it passes through the pre-stage direct expansion section for pre-cooling and the post-stage direct expansion section for re-cooling. The sensing module is used to collect temperature and humidity information; The logic control module generates control commands based on the information from the sensor detection module; The compressor drive module controls the operation of the compressor in the front and rear direct expansion stages according to control commands; The logic control module has a built-in linkage control unit. After both the compressor systems of the current stage and the subsequent stage direct expansion stage are started, if the evaporator coil temperature of any subsequent stage direct expansion stage compressor system is ≤T2 and the running time reaches a preset threshold, the linkage control unit sends a load reduction command to the compressor drive module, controlling the number of compressor systems in the current stage direct expansion stage to decrease by 1. After a set time, if the evaporator coil temperature of any subsequent stage direct expansion stage compressor system is again detected to be ≤T2, the load reduction command is sent repeatedly until the evaporator coil temperature of the subsequent stage direct expansion stage compressor system is >T2. If the evaporator coil temperature of the subsequent stage direct expansion stage compressor system still does not rise, the linkage control unit sends a shutdown command to the compressor drive module, stopping the compressor of the corresponding system in the subsequent stage direct expansion stage whose evaporator coil temperature is ≤T2.

2. The control system for a direct expansion evaporator according to claim 1, characterized in that, In the air handling module, each system of each coil in the pre-stage direct expansion section and the post-stage direct expansion section is equipped with an evaporation temperature sensor. The evaporation temperature sensor is installed on the distribution pipe of the system and is used to collect the temperature at the lowest point of the system. The sensing and detection module integrates the detection data of the evaporation temperature sensor to participate in the system control. The sensing and detection module also includes a fresh air temperature sensor and a room temperature and humidity sensor; the fresh air temperature sensor is used to acquire the fresh air temperature Tfresh air, and the room temperature and humidity sensor is used to acquire the room temperature Troom and the room humidity Hroom; the logic control module receives and stores the above temperature and humidity data.

3. The control system for a direct expansion evaporator according to claim 2, characterized in that, In cooling mode, the logic control module compares the room temperature T_room with the target temperature TSet and the room humidity H_room with the target humidity HSet to generate a compressor start command. If T_room ≥ TSet + T deviation and H_room ≥ HSet + H deviation, the logic control module sends a start command to the compressor drive module to control the unit's compressor system to start.

4. The control system for a direct expansion evaporator according to claim 3, characterized in that, The logic control module has a built-in fresh air temperature judgment unit. When the fresh air temperature Tfresh air is less than or equal to the set temperature T1 and the duration reaches a preset threshold, the fresh air temperature judgment unit sends a restriction command to the compressor drive module to prohibit the start of the compressor system related to the front-stage direct expansion section and only allow the compressor drive module to run the compressor of the related system of the rear-stage direct expansion section. The current stage direct expansion compressor is prohibited from starting, and the compressor drive module starts the subsequent stage direct expansion compressor system; After the system has been running for a specified time, the logic control module acquires the value of the evaporation temperature sensor in the downstream direct expansion section. When the evaporation temperature sensor value of any downstream system is lower than the set temperature T2 and the duration reaches a preset threshold, the module sends a stop command to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value recovers, the module sends a restart command to restart the compressor of the corresponding system.

5. The control system for a direct expansion evaporator according to claim 4, characterized in that, When the fresh air temperature judgment unit of the logic control module is such that the fresh air temperature Tfresh air ≥ T1 and the duration reaches a preset threshold, and the startup conditions are met and there are no alarms in any system, the compressor drive module sends a graded startup command to the compressor drive module. The compressor drive module starts the three compressor systems of the downstream direct expansion section sequentially according to a preset time. When the downstream compressor is running at full capacity and the coil temperature of the downstream direct expansion section is not lower than T2, the compressor drive module starts the three compressor systems of the upstream direct expansion section sequentially according to a set time Time1. During the startup process, if the coil temperature of any downstream direct expansion section is lower than T2, the logic control module sends an adjustment command to the compressor drive module to control the three compressor systems of the upstream direct expansion section to pause loading and switch to unloading. After the compressor in the front-stage direct expansion section starts and the running time reaches a preset threshold, the logic control module obtains the value of the evaporation temperature sensor in the front-stage direct expansion section. When the evaporation temperature sensor value of any system in the front stage is lower than T2 and the running time reaches a preset threshold, the logic control module sends a stop command to the compressor drive module to stop the compressor of the corresponding system. After the evaporation temperature sensor value of the system recovers, the logic control module sends a restart command to restart the compressor of the system.

6. A control method of a direct expansion evaporator according to any one of claims 1 to 5, characterized in that, The method includes the following steps: Step 1: System Initialization: Start the air handling module, sensor detection module, logic control module and compressor drive module, complete self-test and establish connection, and each module enters the standby state; Step 2, Information Acquisition: The sensing and detection module collects data on the evaporation temperature, fresh air temperature, and room temperature and humidity of the front and rear direct expansion sections, and transmits it to the logic control module for storage; Step 3, Cooling Start Judgment: Based on the data from the sensor detection module, when the room temperature and humidity reach the start-up conditions, the logic control module sends a command to the compressor drive module to start the unit compressor. Step 4, Fresh Air Temperature Control: The logic control module determines the fresh air temperature. If it is lower than T1 and continues to reach the threshold, it instructs the compressor drive module to run only the downstream direct expansion compressor. Step 5, Post-stage operation control: After the post-stage starts, the logic control module, based on the data from the sensor detection module, if the post-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop the corresponding system, and restarts after recovery; Step 6, Pre-stage tiered start-up: When the fresh air temperature meets the standard and conditions are met, the logic control module instructs the compressor drive module to start the three downstream compressors first. After the downstream compressors are normal, the upstream compressors will start. If the downstream compressor temperature is too low during startup, the upstream compressors will pause loading and reduce load. Step 7, Pre-stage Operation Control: After the pre-stage starts, the logic control module, based on the data from the sensor detection module, if the pre-stage evaporation temperature is lower than T2 and continues to reach the threshold, instructs the compressor drive module to stop, and restarts after recovery; Step 8, Linkage Control: When both the front and rear stages are turned on, the logic control module, based on the data from the sensor detection module, will gradually reduce the number of front stages if the temperature of the rear stage is too low and continues to reach the threshold; if this is still ineffective, the corresponding system of the rear stage will be stopped.

Images