| With the sustaining, steady, high-speed development of national economy and the improvement of the living standard, it is popular to utilize air conditioner to supply heat in winter and cool in summer. The widely usage of AC which aggravate the burden of power grid is a main cause of the load difference between on-peaks and off-peaks. So, the contradiction between power supply on-peaks and off-peaks becomes increasingly prominent with the economic and social development. However, the application of cool storage technology in small-sized air conditioner, such as residential, will play a considerable role in economic and social benefits.The evaporator and condenser are the main heat exchange devices in small-sized cool storage air conditioning. Ice container whose frame will affect the performance coefficient of air conditioner greatly is the key facility thereof. Some comparative experiments between straight tubes and helical tubes have been taken. It indicates that helical tube is a kind of more effective enhanced heat exchanger than straight tube. Besides, more heat exchange area can be disposed in constant space because of the compact framework. The two-phase flow is very complicated not only for the complication of itself, but also the effects of centrifugal force and torsion torque.Based on the theory guidance, this paper presents a three-dimensional model for the saturated boiling flow of R134a in a helically coiled tube using the numerical simulation. In the condition of constant heat flux, I made a comparative computation of heat exchange coefficient in different flow forms and mass flow rates. In addition, it presents the analysis on the transformation rules of vapor volume fraction, fluid temperature and fluid velocity. The results are well closed to the theory analysis. Therefore, the results can be used as a reference both for the two-phase flow research on boiling heat transfer and the design for evaporating tubes within small-sized ice storage air conditioners. |
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