Browsing by Author "Salta, Carlos Antonio"
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- ItemThe effect of plenum configuration on the performance of air-cooled heat exchangers(Stellenbosch : Stellenbosch University, 1995-01) Salta, Carlos Antonio; Kroger, D. G.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The main objective of this study is to determine the effect of plenum configuration on the performance of an air-cooled heat exchanger (particularly the fan system's operating point). Various plenum configurations, ranging from simple box-shaped plenums to plenums incorporating round-to-rectangular transition pieces, are tested for a normal flow heat exchanger, a delta heat exchanger and an experimental compact heat exchanger referred to as a double delta heat exchanger. The performance of the various heat exchangers relative to each other is also evaluated. The most important conclusions are as follows : The plenum losses (and hence the fan system performance) of a normal flow heat exchanger having a box-shaped plenum are not very sensitive to plenum length. However, a minimum plenum length of 0.4 fan diameters is advised. The plenum losses occurring in the abovementioned fan system result in approximately 28% of the kinetic energy introduced by the fan being dissipated within the plenum. It is also shown that in a well designed air-cooled heat exchanger the reduction in thermal efficiency due to a distortion of the air velocity distribution through it, is small. For the case of a delta heat exchanger system, the plenum losses result in approximately 70% of the kinetic energy introduced by the fan being dissipated within the plenum. Plenum losses occurring within a double delta heat exchanger system result in approximately 95% of the kinetic energy being lost. In both cases the incorporation of a round-to-round diffuser in the plenum configuration results in a decrease in plenum losses and hence a noticeable increase in the fan system performance. The incorporation of a round-to-rectangular diffuser in the plenum configuration also leads to a decrease in the plenum losses. However, due to the poor static pressure recovery characteristics of the round-to-rectangular diffuser, the increase in the fan system performance is not as large as that achieved with a round-to-round diffuser.