A study of fluid flow and heat transfer of three-dimensional plate-fin and tube heat exchangers by the least-squares finite element method

A numerical calculation procedure based on the least-squares finite element method (LSFEM) is employed to study the fluid flow and heat transfer in a 3-D heat exchangers with in-lined and staggered multiple-row (4 rows) tubes. In this study, the fin pitch of the heat exchanger is 8 fins per inch and the fluid flow is assumed steady, incompressible, and laminar with Reynolds number ranging from 200 to 600. In this paper the pressure drop, pressure coefficient, heat transfer coefficient, local Nusselt number and average Nusselt number for different geometric arrangements have been examined in detail. The numerical results demonstrate that the average heat transfer coefficient of staggered arrangement is 10%-30% higher than that of the in-line one; also, it is effected more at low Reynolds number than at the high Reynolds number. The distribution of pressure drop of staggered array is higher than that of in-lined array. The variation of pressure coefficient at tube surface is dramatically for both the staggered and in-line arrangements for the angle less than 90 degree. The local Nusselt number of staggered array is higher 30%-80% than that of in-lined array for the tube row 2 to 4. Overall, the numerical results are in good agreement with the experimental measurement