Heat transfer enhancement through inner grooved copper tubes with different tube parameters

Abstract

This paper presents the evaluation of heat transfer coefficients for the flow of R22 through internally grooved copper tubes. A series of tests were conducted using two types of tubes namely Tube A and Tube B, which have different tube parameters. The straight and horizontal test section of the test apparatus with a length of 3.67 m was heated or cooled by water circulated in a surrounding annulus. Condensation tests were conducted at mass flux rates of 180 to 537 kg/m²s and the vapor qualities ranged from a nominal value of 83% at the test section inlet to 6% at the outlet. Evaporation tests were conducted at mass flux rates of 110 to 404 kg/m²s and the nominal vapor qualities at the inlet and outlet were 0 and 85%, respectively. For both the condensation and evaporation tests, the heat transfer coefficients are found to increase as the mass flux rate increases.