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Experimental Researches on Two Different Heat Transfer Pinch Points of Non-azeotropic Mixtures of Natural Refrigerants in High Temperature Heat Pump

Author: ZhaoXueZheng
Tutor: ZhaoLi
School: Tianjin University
Course: Thermal Power Engineering
Keywords: High Temperature Heat Pump Non- azeotropic refrigerant mixtures Temperature and enthalpy relations Pinch point Experimental study
CLC: TK124
Type: Master's thesis
Year: 2010
Downloads: 57
Quote: 1
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Abstract

For non-azeotropic mixture refrigerant temperature slip and the phase transition temperature and enthalpy relations of these two characteristics, high temperature heat pump units, variable pinch point issues two types of non-azeotropic mixture theory and experimental study. The application working fluid Z1 (17% R290/83% R600, mass ratio) in the heat pump system for the experimental study of the first phase change heat transfer narrow point, experimental results show that: the theoretical calculation similar, Z1 in the condenser side a maximum temperature difference in the evaporator side of the pinch point, and the maximum temperature difference and the pinch point value and its position within the heat exchanger varies with the change of the water flow. The constant conditions in the evaporator side, the emergence of the condenser side of the maximum temperature difference causes the system to cycle efficiency in the condenser side working conditions unchanged, the point of emergence of the narrow-side heat transfer in the evaporator causes the system to cycle efficiency increased ; extended to other refrigerant mixtures, phase curve will be different, but the pinch point and the maximum temperature difference in the heat exchanger, and the same cycle efficiency, ie, the maximum temperature difference reduced efficiency, but can reduce the heat transfer area; pinch point emergence of the increase in cycle efficiency, but requires a larger heat transfer area of ??the loop. Thus, to avoid or to promote the emergence of the pinch point and the maximum temperature difference is to be comprehensive application conditions (air condition and more focus on the evaporator side, the heat pump working conditions and more focus on the condenser side), cycle efficiency and conversion The hot area three factors considered; application of the working fluid Z1, Z2 (50% R290/50% R600, mass ratio) in the heat pump system for the first class of experimental studies of the phase change heat transfer in narrow point, the second type of phase variable pinch point appeared mainly in the working fluid can not be used in the condensation process is completely condensed, due to the emergence of the phenomenon will bring a lot of instability problems, to solve this problem, this paper under steady-state and non-steady-state conditions experiments were conducted. Experimental results show that, under steady state conditions, the working fluid can not be fully condensed to this phenomenon, but it will appear in the condenser can not be fully condensed phenomenon does not occur for the system piping insulation bad or accumulator tank, piping or reservoir after working fluid will condensate exports as condenser Extension completely condensed, this phenomenon will make the system heating capacity and lower heating coefficient should be avoided. And in the non-steady state conditions, there will be a phenomenon of the working fluid due to the second phase change heat transfer narrow point generated in the condenser can not be fully condensed.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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