ICR07-B1-554 THE EFFECT OF FROST ACCUMULATION ON AIR-SIDE HEAT TRANSFER COEFFICIENT IN FINNED-TUBE HEAT EXCHANGERS
Ruiqiu CHEN, Kai ZHU, Jinying TIAN, Xiaofei HOU, Xinjun SU School of Mechanical Engineering, Tianjin University of commerce,Tianjin, 300134, P. R. China
In air-cooling system, frosting is one of the important problem for the development of heat exchanger. By the experimental investigation of heat transfer in air side of finned-tube heat exchanger under frosting condition, it find that the the humidity, fin pitch,wind velocity etc have the effects on the equivalent surface heat transfer coefficient in air-side. The result shows that in a certain range, reduces sharply with the increase of frosting time in the early stage of frosting, and the effects of these parameters on
weaken greatly in the later stage of frosting.
Muut kiinnostavat olivat tuossa
Abstractissa sivulta 171 lähtien.
ICR07-E2-911 IMPROVEMENT OF THE HEATING PERFORMANCE IN A VARIABLE SPEED HEAT PUMP BY APPLYING THE GAS INJECTION TECHNIQUE INTO A TWIN ROTARY TYPE COMPRESSOR
JAEHYEOK HEO1, YONGTAEK LEE1 , SUNIL LEE1,YONGCHAN KIM2
1 Graduate school of Mechanical Engineering, Korea University Anam-Dong, Sungbuk-Ku, Seoul, 136-713, Korea
2 Department of Mechanical Engineering, Korea UniversityAnam-Dong, Sungbuk-Ku, Seoul, 136-713, Korea
For heat pumps used in the cold regions, it is very important to obtain appropriate heating capacity. Several studies have been performed to enhance heating capacity at low ambient temperatures. The heating performance was signifi cantly improved by the application of a variable speed compressor. However, for outdoor temperature conditions below -15°C, it is still diffi cult to acquire enough heating capacity above the rated heating capacity. In this study, a twin rotary type compressor with gas injection was applied to a heat pump system in order to improve the heating capacity at low ambient temperatures. The heating performance of the gas injection cycle was measured and analyzed by varyingoutdoor temperature and compressor frequency. The tested heatingperformance of the gas injection cycle was compared with that of the non-injection cycle.
The heating capacity of the gas injection system was increased by 11~23% with the variation of outdoor temperature. The COP based on equal capacity was also improved by 8~35%.
ICR07-E2-669 EXPERIMENTAL INVESTIGATION ON DYNAMIC DEFROSTING CHARACTERISTICS OF AN AIR SOURCE HEAT PUMP
Xiangcheng TAO, Xianmin GUO, Yiguang CHEN
School of Mechanical engineering, Tianjin University of Commerce, Tianjin, 300134, P. R. China
The defrosting characteristics of an air source heat pump (ASHP) adopting four-way valve inversion circulation were experimentally investigated. The circulation parameters, heat capacity, input power of the ASHP unit and the wall temperature of the evaporator under different outdoor conditions and face velocities of the outdoor heat exchanger were measured. The outdoor air temperature was controlled to be from -15 to 5°C, and the relative humidity from 55% to 90%. The effects of the outdoor environmental parameters and face velocities of the evaporator on the defrosting characteristics were analyzed. The experimental results indicate that the frost accumulation mass is maximum when the outdoor temperature is about 0°C, however the defrosting time and defrosting loss decrease as the outdoor temperature increases. The frost accumulation mass increases as the relative humidity under fixed outdoor dry-bulb temperature increases, but the defrosting time decreases.
Meanwhile, it is also found that the defrosting time and defrosting loss are minimum when the face velocity of the evaporator is 1.3 m/s for the tested ASHP unit.
