Numerical analysis of heat and mass transfer in a compact finned tubes air heat exchanger under dehumidification conditions

Abstract

A simulation model of a fin-and-tube heat exchanger is presented. The effect of the relative humidity, air speed, fin base temperature, and inlet air temperature on the estimation of the overall heat-transfer coefficient and fin efficiency under wet conditions is also investigated. This model considers a non-uniform airflow velocity as well as a variable sensible heat transfer coefficient. List of symbols c p,aMoist air specific heat at constant pressure, J kg -1 K -1 C Condensation factor, K -1 d Thermal diffusivity of vapor in air, m 2 s -1 D Specific diffusion coefficient of vapor in air, m 2 s -1 D t External tube diameter, m D h Hydraulic diameter, m _ E Energy flow rate, W g Acceleration of gravity, m s -2 h Half fin height, m i Specific enthalpy, J kg -1 j Colburn factor for the heat transfer l Half fin length, m Le Lewis number Lv Latent heat of vaporization, J kg -1 m 00 Flux mass density, kg m -2 s -1 _ m Mass flow rate, kg s -1 Nu Nusselt number P f Half fin spacing, m P l Longitudinal tube pitch, m P t Transverse tube pitch, m PrPrandtl number Q t,id ; Q t,r Heat flux for ideal and real fin, W q 00 t

Tube pattern effect on thermalhydraulic characteristics in a two-rows finned-tube heat exchanger

“…This difficulty is fortunately balanced by the development of Computational Fluid Dynamics simulation tools for which the robustness in the description of the flow and heat transfer is more and more proved [7]. For this reason, extensive effort have been devoted to numerical investigations of flow and heat transfer characteristics in finnedtubes heat exchanger during the last decades, see Benelmir and Mokraoui [11]. Modeling the flow and heat transfer in such geometries represents nonetheless a challenge due to the fact that, depending on kinematic and geometrical parameters, the flow can be laminar, turbulent, steady or unsteady.…”