Numerical investigation of conjugate heat transfer in a pillow-plate heat exchanger

•Conjugate heat transfer simulations were carried out for a pillow-plate heat exchanger (PPHX).•A detailed analysis of the thermal partial resistances of a PPHX.•New approaches for the accurate PPHX dimensioning are suggested.•PPHX from aluminium yield significantly better heat transfer performance than PPHX from stainless steel. Pillow Plate Heat Exchangers (PPHX) are composed of several pillow plates arranged parallel to each other, with one flow path inside the plates (inner channel flow) and another in the spaces between adjacent plates (outer channel flow). In research studies published by now, the transport phenomena in these two flow paths have mostly been treated in a separate manner. Such a treatment does not permit to identify important effects, e.g., unfavourable thermal interaction between the inner and outer channel flow caused by predominant recirculation zones, or the influence of the material used for the pillow plate manufacturing. In this work, for the first time, conjugate heat transfer modelling and CFD-based simulations were carried out for a PPHX operated in countercurrent mode. This allowed a detailed analysis of the individual thermal resistances in a PPHX. Based on the results of this analysis, approaches for the correct calculation of these thermal resistances were created.