FLUID TEMPERATURE DISTRIBUTION IN CROSS-FLOW TUBE BUNDLES

A new analytical method is presented for the determination of temperature distribution and effectiveness of heat transfer in different cross-flow arrangements. As an improvement over the known analytical solutions simplified energy balance equations are used. This simplification consists only in their notation but not in representation of the exact energy balance. The demanded accuracy of the thermal analysis is achieved by proper selection of a mean value of fluid temperature outside the tube. For each tube i in the bundle a mean value theta(i) of the dimensionless fluid temperature outside the tube is introduced according to theta(i) = omega theta(i+1/2) + (1 - omega) theta(i-1/2) where theta(i-1/2) and theta(i+1/2) are the local temperatures in front and behind the i-th tube, respectively. With symbol omega a weight coefficient is denoted omega = 1/(1-e(-NTUperpendicular-to/n))-n/NTU(perpendicular-to) The number of tube rows in the bundle is n and the number of transfer units of the outside stream is NTU(perpendicular-to). Through the introduction of the weight coefficient omega, the mathematical operations related to calculation of the temperature field are radically simplified. This enabled the development of the procedure, valid for three codirected cross-flow arrangements (Fig. 1) and any number n of the rows.