Study On Refrigerants And Exergy For Heat Pump Dryers

Drying is widely used in production and lives, but common dryers are energy-intensive. Heat pump dryers have been paid much attention in recent years because of their high energy efficiency and better product quality.The key work in this thesis is as following:(1)The advantages and applications of heat pump dryers are analyzed, and different structures of the heat pump dryers are discussed.(2) The mathematical model of typical heat pump dryers is given, and the optimizing algorithm for the heat pump dryer parameters is also given.(3) A series of heat pump refrigerants (including pure and mixture refrigerants) are selected, and methods to design suitable refrigerants for heat pumps are also developed. Equations to estimate property constants are given which can be good tools used to search for new heat pump refrigerants.(4) Some flammable refrigerants are high efficient, but their flammability brings much danger for their applications. To make full use of such refrigerants, equations for predicting the lowest flammable limit of pure refrigerants and the critical flammable ratio (CFR) of refrigerant mixtures are given.(5) The exergy loss of each component and process of the heat pump dryer (air flow process, compression process, heat transfer process, throttling process et al) is analyzed, and measures are put forward to reduce exergy loss.(6) An experimental heat pump is built up and the performance changes of the heat pump are studied with main operation parameters.To sum up, the main creative work of this thesis is: more than twenty suitable refrigerants for the heat pump dryer, equations to analyze exergy loss and application instructions for the heat pump dryer.