ABSTRAKT

Performance evaluation criteria (PEC) for enhanced heat transfer surfaces enable evaluation of the benefits of heat transfer augmentation relative to the increase in pressure drop as well as maximization of a performance objective for a given set of constraints. The objective can be increasing the heat duty or reducing the size of a heat exchanger, minimizing the pumping power, or obtaining the same performance with a reduced temperature differential. Professor Arthur Bergles did pioneering work in this area and developed a methodology to apply PEC to heat exchangers with various constraints: fixed geometry, variable geometry, fixed pumping power, fixed flow rate, and fixed inlet temperatures. This paper demonstrates the application of PEC to a heat exchanger using a smooth carbon steel (mild steel) tube and an enhanced tube of the same material (Vipertex 1EHT tube). Data taken on a double-pipe heat exchanger at two tube-side flow rates were used to quantify the PEC. The evaluation shows that, depending on the applied constraints, different benefits can be obtained using Vipertex tubes−a heat duty increase of up to 19%, an 18−30% reduced flow rate to achieve the same heat duties, or a change in geometry to achieve an 8−9% increase in heat transfer at the same pumping power.