Augmented dry cooling surface test program: analysis and experimental results [report]

H.L. Parry, L.J. MacGowan, D.K. Kreid, L.E. Wiles, D.W. Faletti, B.M. Johnson
1979 unpublished
A series of experiments was performed using the Pacific Northwest Laboratory (PNL) Water Augmentation Test Apparatus (WATA) to assess the operating characteristics and potential performance of water-augmented dry cooling systems. The work was aimed at 1) evaluating a deluged air-cooled HOTERV plate fin heat exchanger surface proposed for integrated dry/wet cooling systems and 2) using test results to guide the development of a predictive analytical model. In the process, all-dry performance
more » ... dry performance data were obtained for the HOTERV surface as well as for two Curtiss-Wright chipped fin surfaces. The dry heat transfer data indicate that a slotted Curtiss-Wright surface slightly outperforms the HOTERV and nonslotted Curtiss-Wright surfaces based on heat rejection rate per unit of fan power. However, all three surfaces are so close in performance that other factors, such as surface cost and piping and mounting costs, will probably determine which surface is preferred at a given installation. Comparisons of deluged HOTERV performance with dry HOTERV and Curtiss-Wright performance under prototypic conditions have established that deluging can provide considerable heat rejection enhancement, particularly at low ITO and low air humidity. A deluged HOTERV core operating at a 115 0 F primary fluid temperature in 105 0 F air at 10% relative humidity can reject over seven times as much heat as a dry HOTERV core operating under the same conditions at the same air-side pressure drop. Even at 70% relative humidity, enhancement ratios on the order of 2 are seen. Thus, it appears that deluge operation can provide considerable enhancement during those periods of warm weather and resultant low ITO when enhancement of dry cooling systems is most needed. Deluged tests were performed to evaluate the effect of airflow rate, deluge flow rate and core tilt angle on performance. Increased airflow increases both heat rejection rate and required fan power. Optimal airflow rate will thus be determined for a given location by the competing costs of iii heat exchanger surface area versus fan operation. Increased deluge flow rate also increases both heat rejection capability and required fan power. Maximum heat rejection per unit of fan power occurs at a deluge flow of 1.5 to 2.0 gpm per lineal foot of heat exchanger core measured in the direction of the primary tubes. Above a deluge flow of about 3 gpm per lineal foot, deluge water begins to be blown from the surface, particularly if approach air velocity is increased to over 6 ft/sec. Within the experimental uncertainty of the data, changes in core tilt angle from vertical to 16 0 from vertical have a negligible effect on performance. At tilt angles greater than 16 0 from vertical, deluge water tended to separate from the system edge of the core. Thus, tests were performed to greater tilt angles. Surface mounting requirements and tower layout will probably be more important in determining tilt angle than performance. iv • ,. • CONTENTS
doi:10.2172/5984126 fatcat:tkkzeaziefdnfpy7rwukr2v7uq