Modeling and Simulation of a Hybrid Compression/Absorption Chiller Driven by Stirling Engine and Solar Dish Collector

Abstract

In this paper, an evaluation of the performance and operating parameters of a hybrid compression/absorption chiller coupled with a low-capacity solar concentrator is presented. The study was carried out using energy and mass balances applied to each component of each system. The variables evaluated in the hybrid chiller were the cooling power, the supply power, the Coefficient of Performance (COP) of both cooling systems and the ratio between heat and power. The diameter and temperature of the hot spot as well as the performance of the dish collector were evaluated. The changed parameters were the heat removed by each refrigeration system, the condenser temperature, the evaporator temperature, the concentration ratio and the irradiance. Results have shown that the compression system can produce up to 53% more cooling power than the heat supplied to the hybrid system. Meanwhile, the absorption system produces approximately 20% less cooling power than the supplied heat. It has also been found that, for the cooling power produced by the hybrid cooler to be always greater than the heat supplied, the cooling power provided by the absorption system should preferably be between 20% and 60% of the total, with a Stirling engine efficiency between 0.2 and 0.3 and a condensation temperature from 28 to 37 °C. Likewise, it has been found that the compression system can produce cooling power up to 3 times higher than the heat of the Stirling engine hot source, with Th = 200 °C and ηs = 0.3. Finally, it has been found that, in a low-capacity solar concentrator, on a typical day in Mexico City, temperatures in the hot spot between 200 and 400 °C can be reached with measured irradiance values from 200 to 1200 W/m2.

Keywords

• hybrid chiller
• compression/absorption chiller
• Stirling engine
• solar collector