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Because of the practical importance of the problem, a considerable amount ofresearch on heat transfer during subcooled boiling flow has been done in recentyears, and many techniques for prediction of heat transfer rates have beenproposed. Most of these are dimensional equations relating wall superheat topressure and heat flux or to heat flux alone, and then are intended foronly one fluid within a certain range of parameters. Comparatively few attemptshave been made at developing general correlations which may be applicable to awide variety of fluids and operating parameters. The author is aware of onlyone correlation, that by Rohsenow(1) which has been compared to a fairly widevariety of data. However, there are severe restrictions on its general use.Thus the need for a general predictive technique seems evident.

The author's objective was to develop a general correlation to predict heattransfer coefficients during partial and fully developed subcooled boiling withan accuracy comparable to that of single phase correlations which is about +/-30%.Judging by the agreement of the proposed correlation with experimental data,the objective appears to have been substantially fulfilled. About 500 datapoints from 29 data sets (from 18 independent experimental studies) are correlatedwith a mean deviation of 9.5%, with 97.5% of the data within +/-30%. Thesedata include fluids water, R-11, R-12, R-113, ammonia, isopropyl alcohol, n-butylalcohol, methyl alcohol (methanol), and aqueous solutions of potassium carbonatein horizontal and vertical pipes and annuli. Pipe diameters range from 2.4 to27.1 mm and pipe materials include stainless steel, copper, nickel, inconel,and glass. Pressures range from 0.lxl06 to 13.8xl06 N/m², reduced pressure from 0.005 to 0.76, subcooling from 0 to 153 deg C, heat flux from 0.01xl06 to 22.9x106W/m², and mass flux from 0.2xl06 to 87xl06 kg/hm². Thus the range of parameterscovered is quite wide and general applicability appears quite probable.

In the following, the correlation is presented, its development described,and the limits of its applicability explored through data analysis. So thatthe correlation may be viewed in the proper perspective, brief discussions onsome other predictive techniques are also included.

Citation: ASHRAE Transactions, Volume 83, Part 1, Chicago, IL