Design improvement of central cooling plant for energy saving using cooling tower water

Abstract

This paper investigates and recommends design improvement for a central cooling plant to enhance the energy efficiency of the system. A storage tank together with an immersed heat exchanger is installed in the liquid line between the condenser and expansion valve to utilize the make-up water of the cooling tower. The heat exchanger uses the make-up water to reduce the refrigerant temperature leaving the condenser and thus enhance the refrigerant sub-cooling. For this purpose, an existing central cooling plant of a commercial building, located in a hot and dry climate region, is used for experimentation and data collection. The energy consumption and relevant data of the existing central cooling plant were acquired over the course of a typical week in summer. First, theoretical-empirical system models including mechanistic relations between components are developed. A numerical algorithm together with monitored data and mathematical model implemented on a transient system simulation tool is used to predict the performance of the new design under transient loads. The integrated simulation tool was validated by comparing predicted and measured power consumption of the central cooling plant. Comparison of the proposed system with existing cooling plant is included in this paper to demonstrate the advantages of our new configuration. Results show that about 9.7% in average and up to 14% power saving can be obtained by using our design while maintaining the comfort condition inside the building.