The so-called "cold", that is after the condensation of saturated liquid by a device (such as cold) and methods (or measures) were cooled so that its temperature is lower than under the pressure of the saturated condensing temperature, called supercooling. Take undercooled liquid temperature before and after cold temperatures in comparison, difference is "supercooling".

Throttling the refrigerant before a liquid cooled in order to reduce the Flash in throttling process of gas, reducing Flash-the ratio of the volume of gas and increase the refrigeration capacity also improves the return gas superheat, protect compressor against wet stroke operation, there are advantages.

In larger refrigeration systems, in order to lead into the throttle valve of the refrigerant liquid temperature lowered at the throttle or the Flash of a throttle reduction gas, increasing the cooling efficiency, process design after the liquid receiver (throttlevalve throttle systems must have the accumulator) and fitted with the special equipment used for cold--subcooler. Its structure is telescopic, spraying, principle is to use lower than after the condensation of saturated liquid temperature of cooling water cooled again (such as deep water), generally comparable cooling to reduce 3~5DUtemperatures (supercooling as a 3~5DU). Also some small fluoride refrigeration system, as small cold storage,, although no specifically of supercooled device, but put for liquid tube and back tracheal dressing in with insulation, using back tracheal of low temperature reduced for liquid tube in of liquid temperature, also can put a for liquid tube and expansion valve directly installation in warehouse within through, by again cooling reached supercooled of purpose, to improve refrigeration efficiency.While heating the temperature of the suction tube to avoid compressor may produce liquid shock wave steam inhalation.

Capillary system, capillary tubes and suction tube (suction) merged together, welded together, useful hot rubber condoms together, across from the suction tube, andwinding on the suction tube, capillary or pipette directly in a tank through. CapillaryExchange heat with the suction tube, the choke in front of the liquid refrigerant return-air heat exchange pipes of low temperature refrigerant vapor cooling are cooled,so that both the pipeline may be entrained in liquid-liquid shock compressor, and can achieve the purpose of liquid before throttling the refrigerant subcooling. If the condenser is deliberately, set aside space to be cooled again and extreme cold is alsopossible. In standard design, but is not doing, consideration is to minimize the overall size and weight, reducing manufacturing costs. For small or micro-capillary system, is not going to add specialized subcooler.

Don't put whole condensation process points apart to talk, put condensation device of imports or upper said into is "condensation", lower or filter device parts said into is "supercooled", cannot put condensation process of initial temperature and Terminal temperature of poor as "supercooled degrees", that is errors of! gas from condensation device of upper into, gradually and outside for hot Exchange, condensation temperature gradually get reduced, last condensation (liquefied) into liquid, product exists condensation device of tail end or filter device in, this is full of condensation process. Cannot said condensation device of upper is condensation, lower or a parts is "supercooled"; also cannot put condensation device of imports temperature and export temperature subtraction as "supercooled degrees", or put condensation process in the of a paragraph temperature and condensation device of export temperature of poor deserves became "supercooled degrees", this is not appropriate of, even is errors of, misunderstanding has condensation process.

Under certain pressure and temperature is higher than the saturation temperature of steam, superheated steam. Exhaust steam temperature of refrigeration compressors are generally higher than the saturation temperature, the capital belongs to the superheated steam, called "exhaust overheating".

Due to the suction tube (suction) the length and degree of insulation, makes steampass with the outside of the tube and heat, a phenomenon known as "breathe in superheated" or "piping hot". This overheating compressor suction temperature, increases the specific volume of steam inhalation, leads to reduced volumetric cooling capacity, reduced refrigerating capacity of the compressor, refrigerant is bad, on this issue as "hazardous overheating." Therefore, the requirement in the suction pipe must be insulated, to shorten the length of the suction pipe to reduce the hazardous overheating.

Using expansion valve of fluorine in refrigeration systems, thermal expansion valve superheat adjustment opening, a phenomenon known as "useful heat". Similarly, f steam by heat resulting from overheating, is also useful to overheat.

Saturation temperature before overheating and difference in saturated temperatureoverheating, called superheat.