Relationship and Adjustment between the Four Main Components of a Refrigeration System and Refrigeration Capacity

Since the refrigeration capacity of refrigeration equipment in various cold storages can change under different operating conditions, some increase and some decrease. Therefore, a certain margin is reserved in advance during the design to prevent the normal operation of the overall refrigeration capacity of the device from being affected due to excessive reduction in the refrigeration capacity of a certain component under a particular operating condition. Here are the changing trends of the main components when the operating conditions change.

The relationship between the refrigeration capacity of the compressor and the evaporation temperature and condensing temperature is that the refrigeration capacity decreases as the evaporation temperature drops or the condensing temperature rises.

The refrigeration capacity of the evaporator depends not only on the difference between the cold storage temperature and the evaporation temperature, that is, its heat transfer temperature difference, but also on the superheat at the refrigerant outlet (for dry - type evaporators) or the liquid level height (for flooded - type evaporators).

When the cold storage temperature is constant, its refrigeration capacity increases as the evaporation temperature drops.

The performance curve of the condenser's refrigeration capacity shows that when the evaporation temperature or the condensing temperature drops, the refrigeration capacity decreases.

In addition, when the cooling water volume decreases and the cooling water temperature rises, the refrigeration capacity also decreases.

The refrigeration capacity of the expansion valve is related to the pressure difference between the inlet and outlet of the valve and the specific refrigeration capacity of the refrigerant under that operating condition.

Therefore, when the condensing temperature drops, the refrigeration capacity decreases. When the evaporation pressure is too high or too low, the refrigeration capacity also drops.

The change of the evaporation temperature of cold - storage refrigeration equipment is related to the heat load of the cold storage, the heat - transfer area of the evaporator, and the volume of the compressor. When any one of these three conditions changes, the evaporation temperature and pressure of the refrigeration system will inevitably change.

The heat - transfer area mainly refers to the evaporation area of the evaporator, and the change of the heat - transfer area mainly refers to the change in the size of the evaporation area. The influence of the increase or decrease of the evaporation area on the evaporation temperature is basically similar to that of the increase or decrease of the heat load on the evaporation temperature. When the evaporation area increases, the evaporation temperature will rise; when the evaporation area decreases, the evaporation temperature will drop.

Changes in heat load occur frequently. When the heat load increases and other conditions remain unchanged, the evaporation temperature will rise, the low - pressure will also rise, and the superheat of the suction gas will increase.

When the energy of the refrigeration compressor is increased, the suction volume of the compressor will increase accordingly. Under the condition that other conditions remain unchanged, the high - pressure will rise, the low - pressure will drop, and the evaporation temperature will also decrease.

As known from thermodynamics knowledge, there is a corresponding relationship between the temperature and pressure when the refrigerant evaporates. Therefore, the adjustment of the evaporation temperature can be achieved by adjusting the evaporation pressure.

The adjustment of the evaporation pressure can be achieved by changing the opening degree of the throttle valve or adjusting the gas - delivery volume of the refrigeration compressor (for compressors with gas - delivery volume adjustment). For example, closing the opening degree of the throttle valve reduces the circulation volume of the refrigerant, the evaporation volume generated in the evaporator decreases accordingly, and the evaporation pressure decreases accordingly. Conversely, if the throttle valve hole is opened wider, the evaporation pressure will increase accordingly. If the gas - delivery volume of the compressor is changed, the evaporation pressure will also change accordingly.