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Make cryogen
From;    Author:Stand originally
Evaporate inside the evaporator of refrigeration system and from be cooled quantity of heat is absorbed in the object and aerification, deliver quantity of heat the medium all round inside condenser next (water or air) and the working material of itself liquefaction calls labour to pledge, call refrigeration agent again. Commonly used refrigeration agent has Lyons of ammonia, fluorine to wait. Alphabetical “R” and a group of numbers from the back are used so on international for short the symbol will represent refrigeration agent, wait like R12, R22. Whether are pair of atmosphere ozonosphere contained to have the material that destroys effect in making cryogen to identify of late, the elemental code name that contains with place adds a number to represent refrigeration agent, be like: CFC-12(R12) , HCFC-22 (R22) wait.
One, the main demand to refrigeration agent
The main character that refrigeration agent should have should be the vaporization temperature below standard atmosphere (evaporate namely temperature) inferior, condensing pressure is unfavorable and exorbitant (should condense easily) ; Unit volume refrigerating capacity wants big, vaporization latent heat is big, specific volume is minor; Avirulent, do not burn, do not explode, without corrode, use safety; Low-cost, obtain easily. Be destroyed as atmosphere ozonosphere the discovery of the problem, still ask to be not had to atmosphere ozonosphere destroy effect, make global warmth changes potential the value is little.
1, the requirement of thermodynamic nature field:
1) evaporate in what cryogen makes below standard atmosphere temperature wants low, do not exceed commonly - 10 ℃ . Evaporate in the standard the pressure below temperature should prep above or be close to atmosphere force, lest system of air infiltration refrigeration.
2) the condensing pressure that controls cryogen inside working temperature limits is unfavorable and exorbitant, be in commonly (1.2 ~ 1.5) MPa. Condensing pressure is too high, to the intensity of refrigeration equipment the requirement also wants to rise accordingly, and still can bring about compressor power comsumption to increase.
3) QV wants the unit volume refrigerating capacity of refrigeration agent big. Because QV value is great, show in compressor cylinder diameter and journey same situation falls, can acquire larger refrigerating capacity.
4) the critical temperature of refrigeration agent wants some taller, fall in normal temperature or average low temperature namely can liquefacient, the caky temperature of refrigeration agent wants low, so that obtain,evaporate inferiorly temperature.
5) of refrigeration agent evaporate latent heat wants big, aeriform specific volume wants small.
2, the requirement of physico-chemical nature field:
1) the viscosity of refrigeration agent and density want as far as possible small, flow mediumly in order to reduce refrigeration agent in the system obstruction.
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