Comprehensive Study of Compact Heat Exchangers with Offset Strip Fin

Abstract

This chapter is aimed to address the performance of compact heat exchangers with offset strip fin, which have been studied by the researchers in detail for decades. The history and basic features of offset strip fins (OSF) are described first to introduce the fin geometry. Then, the effect of the fin geometry on the performance of the offset strip fin is given from experimental and numerical aspects, respectively. Flow streams evolution under varying offset strip geometries is summarized in order to demonstrate the physical impact on the flow. The thermohydraulic features of the flow in the offset strip fin are investigated by considering the Colburn j-factor and friction (f) factors in diverse flow regimes. Furthermore the criteria, flow area goodness factor j/f, the ratio j/f 1/3 and thermohydraulic performance factor JF, derived from the mentioned dimensionless factors, are also used as a scale of the performance of the structure and reported in the chapter.

Numerical investigation of heat transfer and pressure drop characteristics in an offset strip fin heat exchanger

“…The j-factor falls in all calculated cases as the Re number ascends due to its definition which is given in Eq. (8). The change of the factor is almost the same in all three fin spacing's (s f = 2.10, 2.35, and 2.60 mm).…”

“…By offsetting the fin in the flow direction, it induces a thin laminar boundary layer on the uninterrupted surfaces as well as the form-drag. With regard to the high performance of the OSFs, many researchers have studied this fin-type numerically or experimentally and some of these studies in the literature were presented in books and reviews [5][6][7][8]. They presented wide correlated data for the thermal and hydraulic performance of the CHXs with plain, offset strip, wavy, and perforated fin in 1947.…”