Vapor Compression Heat Pump Using Low Temperature Geothermal Water: a Case Study of Northern Thailand

Abstract

Experimental study on Vapor Compression Heat Pump (VCHP) is carried out with the aims to upgrade shallow depth and low temperature geothermal water to a higher temperature (at least 20 °C higher) suitable for use in drying facilities for agricultural products. Five working fluids, R-22 (Chlorodifluoromethane), R-290 (Propane), R-134a (1,1,1,2- Tetrafluoroethane), R-717 (Ammonia) and R-123 (2,2-Dichloro-1,1,1-trifluoroethane) have been considered and simulated. The simulation results showed that R-123 was the most suitable refrigerant for the heat pump due to its lower high-side pressure and highest coefficient of performance (COP). The R-123 VCHP is capable to upgrade supplied water temperature of 40OC from the water-cooled condensers to hot water temperature of 80 °C. Single stage VCHP using R123 as working fluid is equipped to a drying room of 3.3 x 4.8 x3.2 meters in dimension, at Huai Mak Liam hot spring area in Chiang Rai Province. The shallow depth well of 85 meters supplies water temperatures in and out of the heat pump as 50 °C and 47 °C, respectively. The coefficient of performance of drying room is 2.68 with the room temperature increases from 25 °C to 70 °C within 3 hours.