# Simulation and optimization of a vapor compression refrigeration system

 Author: Chan, Kwok-kwan Title: Simulation and optimization of a vapor compression refrigeration system Degree: M.Sc. Year: 1997 Subject: Refrigeration and refrigerating machineryRefrigeration and refrigerating machinery -- China -- Hong Kong -- Case studiesHong Kong Polytechnic University -- Dissertations Department: Multi-disciplinary Studies Pages: vi, 101, [45] leaves : ill. ; 30 cm Language: English InnoPac Record: http://library.polyu.edu.hk/record=b1250493 URI: http://theses.lib.polyu.edu.hk/handle/200/2779 Abstract: This dissertation described an analytical tool (a digital computer program in C language) developed to simulate an existing vapor compression refrigeration system and to minimize the annual operation cost of electricity and water consumption under the ambient temperature fluctuation in random nature. The minimization was performed by allowing the variation of three operation parameters ( surge drum temperature, intercooler temperature, and condensing water flow rate ). Also, these operation parameters were constrained by the physical conditions of the existing refrigeration system. Two sets of the three operation parameters of the refrigeration system were recommended to achieve the minimum annual operation cost as the average ambient temperature in summer was significantly higher than that in winter. One was for operation in summer and another in winter. The mathematical model of the refrigeration system was composed of the component models, which were interconnected by the conservation laws of energy and mass. The steady-state mathematical model of each component was developed to perform the energy calculation on an hour basis. The models of the components appeared in the form of algebraic functions, typically for heat and mass transfer in terms of pressure and temperature. The least square method, a curve fitting technique, was used to find out the coefficients of the algebraic functions. The raw data for least square method was obtained from the manufacturers' catalogues. The annual operation cost of the system model were expressed mathematically by an objective function which was in terms of the three operation parameters. This objective function was minimized by the "Davidon-Fletcher-Powell" method, an unconstrained optimization method. Although the operation parameters were constrained within the feasible ranges, the physical constraints of the operation parameters were transformed and combined with the objective function. Then, the transformed objection function could be minimized by the unconstrained optimization method.

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