Numerical study of condensation and conjugated heat transfer from flow in a heat exchanger

Abstract

There are many industrial and nonindustrial fields where Plate heat exchangers, PHE, are utilized for their efficient heat transfer ability. Some fields in which PHEs are commonly used include HVAC (Heating, Ventilation, and Air Conditioning), Power Generation, and Refrigeration. The compact size, high heat transfer efficiency, ease of maintenance, and cleaning make them a popular option across various sectors. Hence, it is essential to study and understand the flow and heat transfer in plate heat exchangers to optimize the usage of these systems.

Alfa Laval develops (design, analyze, and manufacture) a wide range of heat exchangers, including gasketed, brazed, and welded plate models. This Master’s thesis concentrated on investigating and laying the groundwork for conducting Computational Fluid Dynamics (CFD) simulations to study heat transfer during the phase change (condensation) process on the primary side, involving the full condensation of propane as it transitions from a gaseous to a liquid state.

The procedure followed in this thesis is as follows: Initially, a Pipe flow, as a first test case, is simulated to gain an understanding of the various parameters involved in Computational fluid dynamics (CFD) analysis. Then, as a second test case, to develop and validate a multiphase flow modeling where a full condensation of the gaseous phase occurs, the Kuhn (1995) [12] experiment is adopted.

The numerical simulation models were created using Ansys Discovery Modeling. Subsequently, the meshing and simulations were carried out using Ansys- Meshing and Fluent (2023R1). The hydrodynamics of the two-phase flow have been solved using both the Mixture- and Volume of Fluid (VoF) methods separately. Mass and heat transfer resulting from phase change (condensation) were handled through the Lee condensation model.