Lingbao Wang

Performance analysis and working fluid selection for geothermal energy-powered organic Rankine-vapor compression air conditioning

BackgroundTo utilize geothermal energy from hot springs, an organic Rankine cycle/vapor compression cycle (ORC/VCC) system was employed for air conditioning and a thermodynamic model was developed.MethodsSix working fluids, R123, R134a, R245fa, R600a, R600 and R290, were selected and compared in order to identify suitable working fluids which may yield high system efficiencies.ResultsThe calculated results show that because of high system pressure for R290 and R134a, R600a is the more suitable working fluid for ORC in terms of expander size parameter, system efficiency and system pressure. In addition, R600a is also the most appropriate working fluid for VCC in terms of pressure ratio and coefficient of performance. R600 and R600a are more suitable working fluids for ORC/VCC in terms of overall coefficient of performance, refrigerating capacity per unit mass flow rate and chilled water yield from per ton hot water.ConclusionsIn sum, R600a is the most suitable working fluid for ORC/VCC through comprehensive comparison of ORC efficiency, expander size parameter, pressure ratio, coefficient of performance, system pressure and chilled water yield from per ton hot water for six different working fluids. However, the flammability of R600a should attract enough attention.

Preparation and Performance Testing of Composite Adsorbents for Solar Adsorption Refrigeration

In order to develop a high-performance adsorbent for solar adsorption refrigeration, a series of composite adsorbents is prepared by impregnating CaCl2 into the pores of silica gel. Seven samples are prepared using various concentrations of CaCl2 aqueous solutions. Sorption properties of the samples are tested with gravimetric method. The test results indicate that both the adsorption amount and adsorption rate of the composite adsorbents increase significantly compared with that of the pure silica gel. The water uptakes of silica gel and composite adsorbent are 1.96 and 8.08 kg/100 kg adsorbents, respectively, with the relative humidity of 20% and adsorption time of 20 minutes. Subsequently, a novel solar adsorption chiller is designed, in which the composite adsorbent is used as an adsorbent and water as a refrigerant. Performance testing of the adsorption chiller shows that the cooling capacity, specific cooling power and coefficient of performance are 1.03 kW, 128.3 W/kg and 0.27, respectively, when hot water temperature, cooling water temperature and circulation time are 90 °C, 35 °C and 15 minutes.