Xianbiao Bu

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.

Preparation of ammonia adsorbent by carbonizing and activating mixture of biomass material and hygroscopic salt

We put forward a new and ingenious method for the preparation of a new adsorbent by soaking, carbonizing and activating the mixture of hygroscopic salt and biomass material. The new adsorbent has high porosity, uniform distribution and high content of CaCl2, and exhibits high adsorption performance. The ammonia uptake and specific cooling power (SCP) at 5 min adsorption time can reach as high as 0.19 g·g−1 and 793.9 W·kg−1, respectively. The concept of utilizing the biomass materials and hygroscopic salts as raw materials for the preparation of adsorbents is of practical interest with respect to the potential quantity of biomass materials around the world, indicating that there would be a new market for biomass materials.

Electricity Generation from Abandoned Oil and Gas Wells

The objective of this study is to demonstrate the feasibility of acquiring geothermal energy using abandoned oil and gas wells. The equations of fluid flow and heat exchange were developed and solved by numerical methods. Computational results indicated that the two main factors of influencing heat exchange and output power were fluid flow rate and geothermal gradient. The net output power is 59.41 kW at a geothermal gradient of 45°C/km and flow rate of 0.04 m/s. The fluid outlet temperature after 10 years of operation is just 0.41°C lower than that of initial time.

Solar radiation on vertical surfaces for building application in different climate zones across China

The global concerns about energy consumption and environmental sustainability elevate the aspiration of applying solar energy to buildings. The information of solar radiation on the building envelope is important in designing the solar devices for building application. In this study, the solar radiation on the vertical surfaces in five major climate zones of China, viz. hot summer and warm winter, mild, hot summer and cold winter, cold, and severe cold, is investigated using the Klein and Theilackers model with monthly average solar radiation measurements on a horizontal surface during 1971–2000. Guangzhou, Kunming, Wuhan, Beijing, and Harbin are selected as the representative cities in the five climate zones. The results show that the peak values of the total solar radiation on the vertical surface in each month occur at different orientations with the azimuth angles during ±90°. For annual utilization, the vertical surface due south is best for the five representative cities, and the deviation in azimu...