Prediction of cooling-coil performance under condensing conditions

The possibility of predicting chilled-water cooling-coil performance under condensing conditions using dry-surface heat transfer correlations is examined. Experimentally determined wet-surface Nusselt number data are presented and compared with dry-surface data obtained from the same cooling coils. The wet-surface Nusselt numbers show considerable scatter; some of the results are higher than the corresponding dry-surface correlations, while others are lower. A sensitivity analysis is presented to illustrate that the wet-surface Nusselt numbers are very sensitive to the uncertainties in the measured inlet dew-point temperature and the measured heat transfer rate. It is demonstrated that the use of dry-surface Nusselt number correlations in a coil model result in wet-surface heat transfer predictions that are generally within 5 percent of the experimentally determined value.