| The refrigeration are-conditioning system's miniaturization and the energy conservation have promoted the development of the strengthened heat transfer technology. The internal grooved tubes in recent years have obtained the widespread value and the development in the refrigeration are-conditioning profession, as they have the merits of the low production cost, the good heat transfer strengthening effect and the small pressure lose. Therefore, the research of heat transfer performance in smooth tubes and internal grooved tubes has the certain theory value and the practical significance.Flow boiling heat transfer characteristics in horizontal smooth tubes and internal grooved tubes of R22 are experimentally investigated.Experiments in smooth tubes R22 are carried out with the mass flux ranged from 150 to 300kg/m~2.s, heat flux from 10 to 35 kW/m~2, evaporating temperature from -5 to 5℃ and vapor quality from 0 to 1. While the flow boiling heat transfer characteristics in internal grooved tubes of R22 are experimentally investigated with the mass flux ranged from 150 to 300 kg/m~2.s, heat flux from 10 to 30 kW/m~2, evaporating temperature from -5 to 5℃ and vapor quality from 0 to 1. The changeful rules of local heat transfer coefficient with the variety of the mass flux, heat flux and evaporating temperature are analyzed and discussed. Local heat transfer coefficients in smooth/internal grooved tubes are compared.The obtained results in smooth tube are used to check five existing empirical correlations for in-tube flow boiling heat transfer available in literature. Kandlikar correlation can predict precisely local heat transfer coefficients of R22 in horizontal smooth tube. Thus, a new correlation based on the Kandlikar's correlation has been put forward by introducing a modification, and the errors between the experiment results and correlation results is within 10%.In this paper, it can also be concluded that the heat transfer enhancement factor of two...
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