New design equations for turbulent forced convection heat transfer and pressure loss in pillow-plate channels

Abstract

Pillow-plate heat exchangers (PPHE) represent a stack of pillow plates characterized by a wavy surface and fully welded construction. The benefits of PPHE over conventional heat exchangers have made them increasingly attractive for numerous applications in the process industry. However, the lack of verified design methods and reference applications for PPHE hinders their widespread application. This work aims at overcoming this “bottleneck” by providing new equations for the thermo-hydraulic design of pillow plates.In particular, design methods for pressure loss and heat transfer are proposed for turbulent forced convection in pillow-plate channels over a wide range of Reynolds numbers (1000≤Re≤8000), Prandtl numbers (1≤Pr≤150) and characteristic geometry parameters (e.g., welding spot arrangement, inflation height). For the determination of heat transfer coefficients, two different approaches are presented. The first approach is based on the method typically suggested in literature, whereby the well-known Dittus-Boelter type power law function (cf. [1]) for the Nusselt number is applied and fitted to numerical data largely obtained in Ref. [2]. The second approach is based on the characteristic flow pattern in pillow plates suggested in Ref. [2]. In this pattern, the initial complex flow is broken down into two simpler flows, which can then be modeled separately. For both methods, the relative deviations between the numerical data obtained in Ref. [2] and in this study are less than 15%.