Zhileng xuebao (Jan 2018)
Heat Transfer Characteristics during Condensation of R134a inside Micro-fin Tubes
Abstract
Experimental study of R134aduring condensation heat transfer inside the micro-fin tube for the condensation temperatures of 35 ℃、40 ℃ and 45 ℃ was made. The mass flux, condensation temperature, structural parameters of micro-fin tube were chosen as influencing factors and the total heat transfer coefficient, water-testing heat transfer coefficient, refrigerant heat transfer coefficient and pressure drop were selected as evaluation indexes. Experimental results show that: the total heat transfer coefficient, refrigerant heat transfer coefficient and pressure drop increase with increasing mass flux, and decreasing condensation temperature and tube diameter, but the water-testing heat transfer coefficient slightly decreases with increasing mass flux and the condensation temperature has a small influence on it. The thermal resistance analysis shows that the water-testing thermal resistance increases and refrigerant thermal resistance decreases with increasing mass flux, and the refrigerant thermal resistance is always less than the water-testing thermal resistance. To evaluate the comprehensive performance of micro-fin tubes, the ratio of refrigerant heat transfer coefficient and pressure drop (the heat transfer coefficient of unit pressure drop) was proposed, results show the ratio decreases first and then increases with the increase of the mass flux, and increases with decreasing condensation temperature and tube diameter in the micro-fin tubes.
