Experimental study and modelling of heat transfer during condensation of pure fluid and binary mixture on a bundle of horizontal finned tubes

Abstract

An experimental investigation was conducted to measure the local heat transfer coefficient for each row in a trapezoidal finned horizontal tube bundle during condensation of both pure fluid (HFC 134a) and several compositions of the non-azeotropic binary mixture HFC 23/HFC 134a. The test section is a 13Â3 (rows  columns) tube bundle and the heat transfer coefficient is measured using the modified Wilson plot method. The inlet vapour temperature is fixed at 40 C and the water flow rate in each active row ranges from 170 to 600 l/h. The test series cover five different finned tubes all commercially available, K11 (11 fins/inch), K19 (19 fins/inch), K26 (26 fins/inch), K32 (32 fins/inch), K40 (40 fins/inch) and their performances were compared. The experimental results were checked against available models predicting the heat transfer coefficient during condensation of pure fluids on banks of finned tubes. Modelling of heat exchange during condensation of binary mixtures on bundles of finned tubes based on the curve condensation model is presented.

Flow fields in shell-and-tube condensers: comparison of a pure refrigerant and a binary mixture

“…They concluded that the difference was greater for lower mass velocities and lower temperature differences, and that the reason is the diffusive transport resistance in the vapour film closest to the gas-liquid interface. Belghazi et al [5,6] recorded a decrease in 30-50% in heat transfer coefficient for the mixture R23/R134a with the same explanation. Jung et al [7,8] measured heat transfer coefficients for the mixture R407C on a single smooth, horizontal tube, and found up to 50% lower heat transfer coefficients than for R22.…”

“…Here, the relative difference between a pure fluid and a mixture is the main factor of importance, and this has not yet been thoroughly investigated. Recent experimental results by Honda et al [3,4] and Belghazi et al [5,6] show little effect of inundation for a mixture on a bundle of low-finned tubes, which means that the heat transfer coefficient is almost constant for the different tube rows, even though lower tube rows receive condensate flow from the tubes above. Therefore, inundation effects are neglected in these calculations and Eq.…”

“…It is not only important to investigate the heat transfer coefficient on the first tube or the progress in a perfect, rectangular tube bundle, which has been done by many researchers experimentally [3][4][5][6][7][8], but it is also important to see what effects the gliding temperature difference and the mass transfer resistances can have on the flow field and on the condensation process in a geometry similar to that in real condensers, and vice versa. It will also be investigated whether a simple modification of the design has an influence on the rate of condensation for the mixture.…”

“…1=4 (9) where l is the thermal conductivity, h fg is the specific enthalpy of vapourisation, T I and T W are temperatures at the phase interface and at the tube wall, respectively, and d eq is an equivalent diameter of the finned tube [21]. According to Brown and Bansal [22], this model sometimes underpredicts heat transfer for high fine densities, but Jung et al [7] and Belgazi et al [5,6] have shown reasonably good agreement for several geometries. Here, the relative difference between a pure fluid and a mixture is the main factor of importance, and this has not yet been thoroughly investigated.…”

Study of Improvement in the Performance of Triple Effect Vapor Absorption System Using Loop Heat Pipes

“…Wanget al [2008]added heat pipes in adsorption water chiller or ice maker initials. His work showed that the adsorption refrigerators are very efficient [10].PrachaYeunyongkul et al [2009]aimedat experimentally investigating the application of a closed loop oscillating heat pipe (CLOHP) as the condenser for a vapor compression refrigeration system [14].R. Rajashree et al [1990]went through a numerical analysis of an unsteady, viscous, laminar, incompressible, two dimensional heat and mass transfer, in the vapour gas region of gas loaded circular heat pipe [20].…”