| Strictly speaking, hot liquid defrosting is a way of high temperature liquid defrosting system. It’s a method suitable for cooling air evaporator, which is proposed by Tianjin university of commerce in 2003. The research and development about this method has been in the refrigerating system, including the machine of low temperature and humidity, constant humidity and temperature. Hot liquid defrosting belongs to the process of frost melting refrigeration. When the system is defrosting, the temperature and humidity of the cold unit has small fluctuation. By recycling the frost cold capacity on the evaporator’s surface, improve the system efficiency during the frost. This paper studies on the possibility and performance of the hot liquid system. Through a lot of experiments, we can grasp the system’s regulation parameters and adjusting performance.This paper established four mathematical model about the main equipments, including refrigeration compressor, condenser, expansion valve, evaporator’s frosting model. On this basis grasp the following relation changes along the tube,including refrigerant compressor capacity, mass flow and working conditions, evaporator pressure drop,evaporation temperature and tube length, wall temperature in the frost process,average frost thickness and tube length, temperature and pressure of the condenser,density of heat flow.It has a guiding role for setting the experiment’s parameters,then we can do it well smoothly.Experimental research included the design of the thermodynamic cooling fan,the design of electromagnetic one-way combination valves, and all over design of the experiment.The construction of the experiment device and experimental data processing and analysis, etc.Experiment content including:in the case of evaporator frost and frost free, the change of the experiment equipment’s refrigerating capacity,COP and consumption; In the process of hot liquid defrosting and thermoelectric defrosting, the temperature change of evaporator which includes liquid pipe and muffler,the wind and return,condenser’s wind and return,compressor’s suction and exhaust, and part of the point pressure changes; Refrigeration evaporator into fluid subcooling changes during the process of hot liquid defrosting; Leeway is touched by the controller related cooling fan melts frost;Temperature of the air-returning pipe at the end of the frost melt,and cold room’s temperature upwards during the frost process,frosted evaporator’s drain time, time difference of the two cooling fans’ operation.Experimental investigation show that hot liquid defrosting is suitable for the cold storage refrigeration system, and when the room temperature is below 20degrees,it can still keep normal;frost speed related to the room’s temperatures.The cooling fan’s closing makes the influence of room’s temperature greatly reduce;Internal heating liquid refrigerant melts frost has high heating efficiency,frost melt time only longer 5～6min than electric defrost;It will keep constant when the room temperature is equal to -15℃,if the temperature higher than -15℃,the melt time will continue drop,if the temperature keeps between -16℃～-20℃,melt time rise 1～-4℃;In the frost melt process,cooling evaporator always maintain larger supercooling degree,this is benefit to improve system’s efficiency.Process control about melt the frost is closely related to the wind pressure switch’s parameter setting,air returning pipe’s rising,drainage time and cold fan running time.For the storage room of low heat load,melt process need lock the thermostat microswitch. |
PDF Full Text Request