Local shell‐side heat transfer coefficients and pressure drop in a tubular heat exchanger with orifice baffles

Abstract

AbstractBy means of a moveable sensing probe previously described2 local shell‐side heat transfer coefficients and friction losses were measured on a model tubular heat exchanger containing orifice baffles. The heat exchanger shell was 6‐in. nominal I.D. and 45 in. in length and contained four tubes in triangular arrangement passing through orifice baffles. Baffle hole diameters of 1‐/16, 1–2/16, 1–3/16, and 1–5/16 in. and baffle spacings of 4.0 and 9.0 in. were studied. Data were taken at several air flow rates for each of the four baffle hole diameters.The average heat transfer coefficient for the region between two central baffles was correlated with an empirical equation based on only two baffle spacings.An increase in the baffle‐to‐tube clearance caused a decrease in heat transfer. An increase in the baffle spacing also resulted in a decrease in heat transfer. Four flow zones in the baffle space are postulated from the analysis of Nusselt number distribution along the tube. The heat transfer characteristics in each of the four flow zones were analyzed in terms of the mechanism of the fluid flow.The pressure‐drop data were correlated in terms of an annular orifice coefficient of discharge and an orifice‐pressure‐drop function. As a result of this study a method was developed by which one can predict the average of the local coefficients at the baffle position from the knowledge of pressure drop across a single baffle.