NUMERICAL MODELING OF TWO-PHASE FLOW PLATE HEAT EXCHANGER

Abstract

The series of the chapter is an attempt to numerically model the two-phase flow flowing through a flat plate Heat Exchanger. Two-phase flow heat exchangers have the ability to transfer energy significantly by exercising the benefits of the latent heat as the working fluid changes phase. Sadly, the flow science behind the process of phase change is very complex. There are notable voids in the requisite understanding of how numerous pivotal parameters are affected by the phase change process. Consequently, a preliminary study modelling a two-phase flow heat exchanger has been performed. Many vital theories, principles have been defined, which are essential to modelling two-phase flows. This investigation yields a primary foundation on which moreover studies can build upon. Condensers, evaporators, boilers, heat pipe etc., are a few of the devices that use two phase flows immensely in their application. Plate heat exchangers (PHE) are those HX that employ plates, mainly metals, because of their high thermal conductivity, for heat transfer separating two fluids exposed to a much larger surface area. The thin, corrugated plates used in Plate heat exchangers are brazed, gasketed, or welded collectively, depending on the utilisation. Detailed work on the thermal performance of plate type heat exchanger has been carried out. An attempt to numerically model the two-phase flow heat exchanger has been part of the present MTech dissertation work. It is found that there is not much research is available to model the two-phase flow heat exchangers numerically. Therefore, a detailed literature review has been carried out to understand the governing equations, flow characteristics of the two-phase, numerical methods used to analyse the thermal performance of two-phase flow heat exchanger. As part of the present dissertation work, numerical work has been performed to investigate the thermal performance of two-phase flow compact heat exchangers. The governing equations were derived using energy balance during heat interaction between the uniform heat flux provided at the microchannel base on the numerical front. The resulting governing equation was solved using the finite element approach. One-dimensional finite element methodology has been implemented to simplify the modelling of HX. The very purpose of modelling of two-phase flow HX is to determine the variation of temperature of heat transfer fluid flowing through the HX. Determination of the heat transfer coefficient of two-phase flow is challenging as it varies with the mass flux and the quality of the liquid vapour mixture. Hence, empirical relation discovered in the past research and correlations developed by Warrier et Al. is used. The FEM model was solved in C++ to obtain temperature variation of heat transfer fluid (water) along the length of the microchannel length.