Evaporative condenser control in industrial refrigeration systems

This paper is a result of a research project which focused on optimization of an existing industrial refrigeration system for a large two-temperature level cold storage distribution facility located near Milwaukee, Wisconsin. This system utilized a combination of single-screw and reciprocating compr essors (each operating under single-stage compression), an evaporative cond enser, and a combination of liquid overfeed and direct expansion evaporator s. A mathematical model of the existing system was developed. The model was validated using experimental data recorded from the system. Subsequently, the model served as a tool to evaluate alternative system designs and opera ting strategies that lead to optimum system performance. The methods, analy sis, and results presented in this paper focus on evaporative condenser siz ing and head pressure control. Operating system head pressures that minimiz e the energy costs of the system were found to be a linear function of the outdoor wet-bulb temperature. A methodology for implementing the optimum co ntrol strategy is presented. Simulation results for the annual performance of the refrigeration system investigated in this project show a reduction i n annual energy consumption by 11% as a result of the recommended design an d control changes. (C) 2001 Elsevier Science Ltd and IIR. All rights reserv ed.