Simulating Calculation Of The Auto-cascade Refrigeration System Applied In The Air Conditioner And Analysis Of Stress In High Pressure Piping

Currently, most of the single-stage vapor compression refrigeration systemsemploy R410a as their refrigerant, which achieve the control of temperature andhumidity through the heat exchange between the air coming from indoor unit and theevaporator. Although it can offer the temperature that meets people’s requirement, it isdifficult to achieve precise control of temperature and humidity only by using aevaporator, leading to the temperature and moisture deviating the anticipated target.Meanwhile, the refrigerant in the refrigeration system maintains isothermalcondensation and evaporation, which may increase differences in temperature andirreversibility of the cycle to a great extent, resulting in the fall of COP and waste ofenergy.Based on the existing problems of the air conditioning system, a new type of airconditioning system for achieving the independent control of temperature and humidityis proposed, which is designed according to auto-cascade refrigeration system and couldeasily implement two-zone characteristics. The system gives consideration to theprocess of temperature and humidity, and avoids the loss which is usually caused in theconventional air conditioning system because of the combined treatment of temperatureand humidity, and also for this system，energy saving effect is remarkable. In the paper,this control system of temperature and humidity uses two independent regulator toovercome the problem that the conventional air conditioning system is not easy to meetthe human body’s requirements for temperature and humidity, and to avoid thephenomenon that the indoor humidity is too high or too low. So in the article theresearch and analysis of the system has been done from the following aspects:①Based on the requirements of selection to CFCs and the glide of thetemperature, two suitable refrigerants are employed;②Facing the problem that the conventional gas equation of state is not able todescribe the gas-liquid two-phase relationship P-V-T when the substance is in two-phasestate, a equation of state is choosed and applied in the calculation of thermodynamicparameters;③Through the program module of calculation of physical properties about mixedrefrigerants, the calculation of the basic thermal properties of the refrigeration cycle iscompleted, which can be prepared for the selection of equipment of the system; ④Physical model of auto-cascade refrigeration system is created and thesimulation program of the gas-liquid equilibrium is compiled. Through the analysis onthe influence of circulating concentrations and the compressor pressure ratio on thecoefficient of performance of the refrigeration system, the optimal concentration andcompressor pressure ratio is found out in given condition;⑤Taking into account the potential risk of the pipe of high pressure in the system,experimental study and the simulation of CAE are completed on the stress of theexhaust pipe.