1. Supercooling/subcooling degree
Supercooling refers to further cooling the refrigerant that has been condensed into a saturated liquid so that its temperature is lower than the temperature of the saturated state under the pressure. This process can be seen as a further cooling step beyond the normal condensation temperature.
Subcooling is a measure of the degree of supercooling, specifically defined as the difference between the actual temperature of the liquid after supercooling and the saturation temperature of the liquid under the same pressure. In other words, if a liquid is cooler than the temperature at which it should theoretically start to solidify (or remain a saturated liquid) at its current pressure, then this additional low temperature difference is called subcooling.
Why subcooling is needed
Improved efficiency: Supercooling can significantly reduce flash gas (that is, part of the liquid evaporates into gas) produced by a sudden drop in pressure when the refrigerant is throttling (such as through an expansion valve or capillary tube). These flash gases occupy more volume but cannot effectively contribute to the cooling capacity, thereby reducing the efficiency of the refrigeration system. Subcooling can reduce the proportion of flash gas, so that unit mass of refrigerant provides more cooling capacity.
Optimize system stability: By controlling the degree of subcooling, the operation of the refrigeration system can be stabilized, temperature fluctuations reduced, and overall reliability and control accuracy improved.
The meaning of subcooling
Improve cooling efficiency: By reducing unnecessary phase change losses, the system can achieve the same cooling effect with lower energy consumption.
Extend equipment life: Avoid compressor damage due to liquid hammering, reduce maintenance frequency, and extend the service life of the entire system.
Enhanced system responsiveness: Stable subcooling helps the system respond quickly to load changes, especially in situations where rapid cooling is required.
Energy saving and emission reduction: Reduce energy consumption while meeting the same refrigeration needs, complying with modern energy saving and environmental protection requirements.
2. Overheating/overheating degree
Superheating means that under certain pressure conditions, the temperature of refrigerant steam exceeds the temperature of saturated steam under that pressure. The refrigerant steam at this time is called superheated steam, and superheating is common in the exhaust stage of the compressor in the refrigeration system.
The degree of superheat is a measure of the degree of superheat, specifically defined as the difference between the temperature of superheated steam and the temperature of saturated steam at the same pressure. That is to say, the degree of superheat is the temperature value of that part of the superheated steam whose actual temperature is higher than its saturation temperature.
Why is superheat needed?
Avoid liquid hammer: In the refrigeration system, an appropriate amount of superheat can ensure that the steam sucked into the compressor is dry, preventing wet steam or liquid refrigerant from entering the compressor, thereby preventing liquid hammer. Liquid slugging may cause compressor damage, reduce system efficiency, and even damage equipment.
Regulating control: In refrigeration systems using expansion valves, superheat is used as an important feedback signal to regulate the opening of the thermal expansion valve. By controlling the degree of superheat, the flow of refrigerant can be adjusted more accurately, thereby controlling the cooling effect of the evaporator and maintaining stable operation of the system.
Improve system efficiency: Appropriate superheat can help reduce the situation where the refrigerant is not completely evaporated at the end of the evaporator and is sucked into the compressor. This can increase the cooling capacity per unit mass of refrigerant, thereby improving the overall refrigeration efficiency of the system.
The meaning of superheat
Ensure compressor safety: By avoiding liquid slugging, superheat protects the compressor from damage and extends equipment life.
Improve system stability: Through precise control, superheat helps maintain the stability and reliability of system operation, ensuring the continuity and consistency of the cooling effect.
Optimize energy efficiency: Reasonable control of superheat can avoid unnecessary waste of energy and improve the system energy efficiency ratio while ensuring the cooling effect.
Convenient diagnosis and maintenance: Monitoring of superheat is also an important parameter to determine whether the refrigeration system is operating normally. Abnormal superheat may be an indication of system failure, which helps to detect problems in time and perform maintenance.
