A Model of the Coolant Transverse Thermal Conductivity Ideal Displacement in the Direct-Flow Plate Heat Exchangers

Abstract

The paper presents solution to the Graetz problem for the ideal displacement hydrodynamic mode taking into account the heat carrier transverse thermal conductivity at the constant thermophysical parameters in the 2d direct-flow plate heat exchanger heat-insulated section, where heat is transferred through a thermally thin surface. It supposes that the flows Reynolds numbers provide their laminar flow, while the thermal initial section length is much longer than the hydrodynamic initial section length. Local heat transfer coefficients are identified based on the Newton --- Richmann law with subsequent averaging along the plate heat exchanger section length. Comparing computation results of the integral Nusselt number and computation using the Mikheev formula for the laminar flow regime shows somewhat underestimated values of the Nusselt number computed using the Mikheev formula, which is not considering conjugate nature of the heat transfer in a plate heat exchanger. The obtained solution of the Graetz problem makes it possible to assess correctness of the ideal displacement model without taking into account the coolant flow transverse thermal conductivity in a direct-flow plate heat exchanger based on the axial temperature profiles in the hot and cold coolant flows. The paper shows that their difference is observed in the input region due to the normal temperature gradient to the dividing boundary between the coolants. It demonstrates that it becomes possible to describe the coolant flows temperature profiles in a direct-flow plate heat exchanger with satisfactory accuracy using the ideal displacement model without taking into account their transverse thermal conductivity

Please cite this article in English as:

Ryazhskikh A.V., Krasnov A.A., Ryazhskikh V.I. A model of the coolant transverse thermal conductivity ideal displacement in the direct-flow plate heat exchangers. Herald of the Bauman Moscow State Technical University, Series Mechanical Engineering, 2024, no. 4 (151), pp. 160--174 (in Russ.). EDN: ZTHRUH

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