Experimental study on the heat transfer and pressure drop of a cross-flow heat exchanger with different pin–fin arrays

Abstract

In this study, convective heat transfer and pressure drop in a cross-flow heat exchanger with hexagonal, square and circular (HSC) pin–fin arrays were studied experimentally. The pin–fins were arranged in an in-line manner. For the applied conditions, the optimal spacing of the pin–fin in the span-wise and stream-wise directions has been determined. The variable parameters are the relative longitudinal pitch (SL/D = 2, 2.8, 3.5), and the relative transverse pitch was kept constant at ST/D = 2. The performances of all pin–fins were compared with each other. The experimental results showed that the use of hexagonal pin–fins, compared to the square and circular pin–fins, can lead to an advantage in terms of heat transfer enhancement. The optimal inter-fin pitches are provided based on the largest Nusselt number under the same pumping power, while the optimal inter-fin pitches of hexagonal pin–fins are ST/D = 2 and SL/D = 2.8. Empirical equations are derived to correlate the mean Nusselt number and friction coefficient as a function of the Reynolds number, pin–fin frontal surface area, total surface area, and total number. Consequently, the general empirical formula is given in the present form. $$ Nu_{D} = a(Re_{D} )^{b} \left( {{\frac{{N_{t} A_{f} }}{{A_{\text{total}} }}}} \right)^{c} \quad {\text{and}}\quad f = a(Re_{D} )^{b} $$