Xiufeng Gao

Development and Application of Engineering-Scale Solar Water Heater System Assisted by Heat Pump

An engineering-scale solar water heater system assisted by heat pump was developed based on a modularized structure. The subunits of modularized system include vacuum solar energy collectors, air source heat pump, heat storage & supplying system and control panel. All devices could be controlled and monitored centrally. Energy source of this system was composed of solar energy (70%), air thermal energy (20%) and electric power (10%). The system has advantages of high average annual comprehensive energy efficiency and elementary energy utilization efficiency. The product can be employed in central heat water supplying project with a capacity of more than 6 ton, in such facilities as residential districts, hotels, restaurants, dormitories, bathing centers and so on. The economical efficiency is better as the scale is bigger. The project has been supported by innovation funds of Science and Technology of Chinese Ministry of Science and Technology (MOST), being applied in a residential district successfully as a demonstration project of renewable and new energy by Chinese Ministry of Construction.

Application of the Geometry of Conjugate Curves to the Design of Internal-Meshing Rotary Compressors

The internal-meshing rotary compressor can be applied to the CO2 transcritical refrigeration cycle due to its simple structure, self-balanced initial mass, and high pressure endurance. Because of the different fluids transmitted by compressor and pump, the design method of the internal meshing rotary pump cannot be entirely and directly employed. In order to simplify the further study of the internal-meshing rotary compressors, the essential profile equations for the inner and outer rotors are derived and explicitly formulated based on the equidistant curve of curtate epicycloid and the multi-section circular arc, respectively. Then, the relationship between the meshes of the inner and outer rotors, the position of the instantaneous center, the meshing range of the tooth tip arc, and the modification of the profiles are discussed. These basic geometric theories are expected to lay the principles for the design of the compressor of interest.

Annual Operating Characteristics of Solar Central Water Heater System Assisted by Heat Pump

The solar central water heater (SCWH) could supply hot water for massive users effectively and reliably. A SCWH assisted by heat pump (SCWHP) was proposed by replacing the electrical heating appliance with the heat pump. The heat pump could grantee that SCWH woks under any conditions and energy consumption could be reduced sharply. Because the climate situation is quite different between the southern part and the northern part of China, annual operating property of SCWHP would be rather different placing the equipment in different regions. However, few studies focus on this aspect. In the present paper, based on the meteorological data in Xi’an and Guangzhou city, 2005, a proper mathematical model calibrated by some experimental data was established to simulate the annual performance coefficient, input power of SCWHP respectively. Annual operating properties of the same apparatus placed in the two regions were also compared.