NUCLEATE POOL BOILING OF LIQUID MIXTURES

Abstract

An experimental investigation of heat transfer in pool boiling of pure liquids : distilled water, acetic acid, and acetone; and binary mixtures: water-glycerine, water-ethylene glycol, water-acetic acid, and acetone-water was carried out at 1 atmosphere pressure. Acetic acid and acetone were of chemically pure grade; whereas glycerine and ethylene glycol of commercial grade. Two test sections of brass tubes of 25.6 mm., and 27 mm. outside diameter were used. The outer surface of smaller diameter tube was silver-plated to resist the corrosive action of acetic acid. The test section was oriented horizontaUy in the pool of liquid in the vessel. Liquid and surface temperatures were measured by means of copper-constantan 3 3 thermocouples. Heat fluxes in the range of S.9 x 10 to 39.97 x 10 2 Kcal/hr.m were used. Liquid temperatures were varied to cover from non-boiling through subeooled to saturated boiling regions. The data were taken for wide range of compositions for all the binary mixtures. Li all the series of test runs the heat flux was approached progressively to the highest value starting at a low heat flux. The experimental data on the pool boiling of saturated water have been found to compare v/ell with the data of others (30, 49, 57, 58) at 1 atmosphere pressure. The experimental data on the saturated boiling of water-ethylene glycol mixture showed a good agreement with the data of Sternling and Tichacek (-15). 11 The experimental data on boiling of saturated binary mixture showed a minimum in the values of heat transfer coefficient when plotted against the concentration of more volatile component. The concentration corresponding to this minimum value of heat transfer coefficient compared well with the predicted value by the method of Grigorev (18), Tolubinskii et al (14) and van Stralen (16) for all the mixtures. As a result of data analyses, the following correlation has been found best to represent the experimental data on subeooled and saturated boiling of 4 binary liquid mixtures studied in the present investigation with a standard deviation of 31.88 %and average deviation of 31.84 %. 0.6 -0.5 0.37 -0.034 NuB = 0.0576 (PeB) (K^) (K, ) {KQ) The maximum error of + 31 % covered about 95 %:l 697 data points. The experimental data on subeooled and saturated pool boiling of '. pure liquids have been correlated by the following equation with a standard deviation of 20.54 % and average deviation of 20.16 %. 0.6 -0.5 0.37 NuB =0.084 (PeB) (K ^ (Kt ) About 133 data points were found to be represented by the above correlation within a maximum error of + 24 %. The merit of this correlation has been examined with respect to other correlations available in the literature.