Numerical Study of the Unsteady State Cross Flow Heat Exchanger with Variable Fluid Parameters

Noor Mohammed, Rehab

	Numerical Study of the Unsteady State Cross Flow Heat Exchanger with Variable Fluid Parameters
Iraqi journal of mechanical and material engineering
Article 1, Volume 11, Issue 2, 2011, Pages 196-219
Author
Rehab Noor Mohammed
Abstract
ABSTRACT A numerical model for the unsteady state cross flow heat exchanger with variable fluid parameters is presented. The model contains many sophisticated assumptions that always avoided in the traditional analyzing of cross flow heat exchanger like variation of fluid properties (density, viscosity, thermal conductivity and convection heat transfer coefficient) and three dimensions unsteady state. The hydrodynamic properties for both fluids are taken as fluid temperatures dependence. The heat transfer from the hot fluid to the surrounding cold fluids, and the heat exchanged between the cold fluid and the surrounding hot fluids channels and surrounding cold fluids ducts are taken in account. The air is used as cold fluid, while the water as hot fluid. A numerical analysis by using Finite difference method is used to solve the governing equations for both hot and cold fluids. The results shows that at small values of dimensionless X-xis (X = ΔX - 3ΔX) (ΔX = 0.021625), the hot fluid temperature decreases at a constant value of dimensionless Y-Axis (height). The hot and cold fluid temperature lines are curved and lower values of the temperature in the left side (X = ΔX - 3ΔX) and higher values of the temperature in the right side (X = 5ΔX - 8ΔX). The hot and cold overall effectiveness of the system increase with increase number of the cold duct per pass (ncp).
Keywords
heat transfer; Heat exchanger; fluid flow

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