Adjustment of chiller expansion valve
There is a main accessory in the chiller: the expansion valve, the thermal expansion valve can perform automatic adjustment within a certain working condition, but it needs to be adjusted during the debugging of the refrigeration system. When the expansion valve enters normal operation, it can Correctly adjusted automatically.
Regardless of whether it is an air-cooled chiller or a water-cooled chiller, the adjustment of the thermal expansion valve is to adjust the pressure of the spring by adjusting the adjustment rod, that is, to adjust the static assembly superheat of the expansion valve, and the adjustment rod is screwed inwardly to be a compression spring; The adjustment lever is rotated outward to release the spring. Rotate the adjustment lever clockwise to advance it inward, and counterclockwise to adjust it to rotate out.
When the operation of the refrigeration system is adjusted, the direction and range of the expansion valve adjustment can be judged from the level of the evaporation pressure. When the evaporation pressure is higher than the set value, that is, when the flow rate of the expansion valve is too large, it should be adjusted appropriately (turning the adjustment lever clockwise); when the evaporation pressure is lower than the set value, that is, when the flow rate of the expansion valve is low, it should be appropriate. Turn up (turn the lever counterclockwise).
During the adjustment process of the expansion valve, we should pay attention to the different physical phenomena of the compressor under different operating conditions and ambient temperature. For example, in the case of (high temperature temperature -10 °C - +10 °C), (medium temperature -10 °C - -20 °C), (low temperature -20 °C - 45 °C), the evaporation pressure of the compressor is expressed in the suction The frosting on the pipe is different. During the process of commissioning the expansion valve, the opening degree of the expansion valve (ie the flow rate) should be adjusted according to the load. This process requires the accumulation of experience. When adjusting the expansion valve, a low pressure gauge on the compressor suction line can be used to observe the change of the suction pressure (equivalent to the evaporation pressure).
Adjusting the setting range of the expansion valve can generally be carried out in two steps. When starting the operation, it is coarse adjustment. Each adjustment can rotate the adjustment rod once, about one turn (360 °C), when the working temperature of the refrigeration system is close to the given value. If it is less than the given value, fine adjustment should be made, and the adjustment lever can be rotated 1/2-1/4 circle (180°-90°).
The following three pictures show three different superheat states of the refrigerant at the evaporator and compressor suction ends when the expansion valve opening adjustment is different.
Basic concept: Superheat = return air temperature - evaporation temperature : Superheat = 10 ° C - 4 ° C = 6 ° C: Superheat is the temperature difference, not the temperature. The best time to read the superheat; stable high load, stable low load, equipment before temperature or pressure shutdown, before defrost, especially when there is liquid return.
Due to the delay of the transfer of the temperature sensor (thermal inertia), each time after the adjustment, the system should be operated for a minute or ten minutes depending on the capacity of the refrigeration system. Observe the change in the inspiratory pressure to determine the next adjustment direction. In short, the adjustment of the expansion valve is a more detailed work that requires patient observation and analysis. In order to adjust the expansion valve.
Regardless of whether it is an air-cooled chiller or a water-cooled chiller, the adjustment of the thermal expansion valve is to adjust the pressure of the spring by adjusting the adjustment rod, that is, to adjust the static assembly superheat of the expansion valve, and the adjustment rod is screwed inwardly to be a compression spring; The adjustment lever is rotated outward to release the spring. Rotate the adjustment lever clockwise to advance it inward, and counterclockwise to adjust it to rotate out.
When the operation of the refrigeration system is adjusted, the direction and range of the expansion valve adjustment can be judged from the level of the evaporation pressure. When the evaporation pressure is higher than the set value, that is, when the flow rate of the expansion valve is too large, it should be adjusted appropriately (turning the adjustment lever clockwise); when the evaporation pressure is lower than the set value, that is, when the flow rate of the expansion valve is low, it should be appropriate. Turn up (turn the lever counterclockwise).
During the adjustment process of the expansion valve, we should pay attention to the different physical phenomena of the compressor under different operating conditions and ambient temperature. For example, in the case of (high temperature temperature -10 °C - +10 °C), (medium temperature -10 °C - -20 °C), (low temperature -20 °C - 45 °C), the evaporation pressure of the compressor is expressed in the suction The frosting on the pipe is different. During the process of commissioning the expansion valve, the opening degree of the expansion valve (ie the flow rate) should be adjusted according to the load. This process requires the accumulation of experience. When adjusting the expansion valve, a low pressure gauge on the compressor suction line can be used to observe the change of the suction pressure (equivalent to the evaporation pressure).
Adjusting the setting range of the expansion valve can generally be carried out in two steps. When starting the operation, it is coarse adjustment. Each adjustment can rotate the adjustment rod once, about one turn (360 °C), when the working temperature of the refrigeration system is close to the given value. If it is less than the given value, fine adjustment should be made, and the adjustment lever can be rotated 1/2-1/4 circle (180°-90°).
The following three pictures show three different superheat states of the refrigerant at the evaporator and compressor suction ends when the expansion valve opening adjustment is different.
Basic concept: Superheat = return air temperature - evaporation temperature : Superheat = 10 ° C - 4 ° C = 6 ° C: Superheat is the temperature difference, not the temperature. The best time to read the superheat; stable high load, stable low load, equipment before temperature or pressure shutdown, before defrost, especially when there is liquid return.
Due to the delay of the transfer of the temperature sensor (thermal inertia), each time after the adjustment, the system should be operated for a minute or ten minutes depending on the capacity of the refrigeration system. Observe the change in the inspiratory pressure to determine the next adjustment direction. In short, the adjustment of the expansion valve is a more detailed work that requires patient observation and analysis. In order to adjust the expansion valve.
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