AXIAL CONDUCTION IN A THICK-WALL MATRIX HEAT-EXCHANGER

Solutions are developed for temperature distributions and ineffectiven ess for a high Ntu matrix heat exchanger having simultaneous axial con duction in the single phase (matrix/fluid) flow channels and separatin g wall. A scale analysis of the governing equations shows a large disp arity in length scales for the conduction and convection effects, thus indicating a singular perturbation problem. Solutions for both balanc ed and imbalanced flow are obtained by analytical methods with appropr iate scaling so that all terms of the solution are well behaved in the limit of large Ntu. The limiting cases of only wall conduction and on ly matrix conduction are treated, the results from which are favourabl y compared with past works. Ineffectiveness resulting from simultaneou s matrix and wall conduction from the present work is compared with a traditional heat exchanger model for axial conduction. Good agreement is found for only small ratios of axial and wall conductance to Ntu. F inally, the results are compared with earlier laboratory data. These d ata are found to be bracketed from below by the results of this work a nd, from above, by an earlier model for high Ntu performance which neg lected axial conduction.