Experimental investigations on boiling of n-pentane across a horizontal tube bundle: two-phase flow and heat transfer characteristics

This paper presents the heat transfer characteristics obtained from an expe rimental investigation on flow boiling of n-pentane across a horizontal tub e bundle. The tubes are plain with an outside diameter of 19.05 mm and the bundle arrangement is inverse staggered with a pitch to diameter ratio of 1 .33. The test conditions consist of reduced pressure between 0.006 and 0.01 5, mass velocity from 14 to 44 kg/m(2)s, heat flux up to 60 kW/m(2) and vap or quality up to 60%. The convective evaporation is found to have a signifi cant effect on the heat transfer coefficient, coexisting with nucleate boil ing. An asymptotic model allows the prediction of the heat transfer data wi th a fitted value of n =1.5. A strong mass velocity effect is observed for the enhancement factor, implying that the correlations available from the l iterature for the convective evaporation will fail in predicting the presen t data. This effect decreases as the mass velocity increases. (C) 1999 Else vier Science Ltd and IIR. All rights reserved.