Pool Boiling Heat Transfer Characteristics on Twisted Tube Bundles in a Flooded Evaporator

Abstract

The objectives of this paper are to study the pool boiling heat transfer characteristics of twisted tubes in the flooded evaporator. The twisted tubes are processed from common circular evaporating tubes with an outer diameter of 15.88mm. The outer major axis diameter, minor axis diameter, wall thickness and length of the twisted tube are 19.50mm, 11.28mm, 1.09mm, and 3310mm, respectively. The outside tube pool boiling heat transfer coefficients, tube side Reynolds numbers, the wall superheat, the saturation temperature of refrigerant and the heat flux are considered as the key parameters. The results show that pool boiling heat transfer coefficient data increase with , and , respectively, and decrease as the wall superheat increases. It can be found in the case study that the overall heat transfer coefficient of twisted tube flooded evaporator (TFE) is about 1.15 times as high as the one of common flooded evaporator (FE) with a same heat capacity. It is proved that an application of the TFE in the water-cooled screw chiller can be feasible.