Prediction and measurement of the performance of spray cooled heat exchangers

[摘要] ENGLISH ABSTRACT:In the present study various mathematical models have been developed for the analysis ofspray cooled finnned-tube heat exchangers. These models range from simplified modelsbased on the work by Kreid et al. [78KR1], Nakayama et al. [88NA1] and Erens et al.[90ER1] to a more comprehensive model based on the work by Poppe [84P01].Computer programs were written to evaluate the performance prediction of these modelson spray cooled heat exchangers in the vertical air flow mode.Experimental tests were conducted on a four-row finned-tube heat exchanger in a verticalair /water mist flow to verify the mathematical models and it was found that the performanceof this heat exchanger could be predicted within 20 per cent using the accurate model.Significant performance enhancement (up to 3.5 times the dry performance) was found byspraying relatively small amounts of water onto the heat exchanger. The spray watermassflow rate was found to have a significant effect on the two phase pressure drop acrossthe heat exchanger.The present study indicated certain important factors which have to be taken intoconsideration when designing spray cooled heat exchanger units. These include thegeometry of the finned-tubes, the temperature difference between the process water and theoptimum air and the air /spray water ratio.

[发布机构] Stellenbosch University