DESIGN AND DEVELOPMENTOF SHELL AND TUBE TYPE HEAT EXCHANGER BY USING CFD WITH FINAL RESULT

MECHANICAL ENGINEERING

The design and Analysis of Heat Exchanger is carried out with a major consideration in terms of Mass flow of the fluid to be distributed uniformly at the inlet of the exchanger on each side that is, fluid side and throughout the core. But, in actual practice, the flow Non-Uniformity is more common and significant which reduces the desired heat exchanger performance. Non- Uniformity is the non-uniform distribution of mass flow rate on one or both fluid sides in the heat exchanger core. The major feature of gross flow Non-Uniformity is that non uniform flow occurs at the macroscopic level due to poor header design or blockage of some flow passages during manufacturing, including brazing or operation. Non-Uniformity causes a significant increase in heat exchanger pressure drop and some reduction in heat transfer rate as well. For Analysis and study purpose, the commercial Computational Fluid Dynamic (CFD) package, Fluent was utilized for modeling the tubular single pass heat exchanger with different tube arrangements namely four tube in-line arrangement, two tube in-line arrangement and square pitch tube arrangement. In each arrangement both flow Non-Uniformity and uniformmass flow distribution are considered. In heat transfer terminology there appear two mean temperatures namely cross-sectional mean temperature and adiabatic mean temperature. The cross-sectional temperature is the arithmetic mean of all tube side temperatures and the adiabatic mean temperature is weighted mean of tube side temperatures. Investigation is carried out to study the cross sectional mean temperature and adiabatic mean temperature profiles in the computational domain, tubular single pass heat exchanger for flow Non-Uniformity or uniform mass flow distribution on tube side and ideal plug flow on shell side.It is investigated that for uniform mass flow distribution on tube side and ideal plug flow on shell side, there is no difference the cross-sectional mean temperature and adiabatic mean temperature. But for Non-Uniformity without back flow on tube side and ideal plug flow on shell side, the two mean temperatures have same value at the cross-section ξ=0. For Non-Uniformity with back flow on tube side and ideal plug flow on shell side, the temperature jump occurs at the beginning of the calculation domain. The available computational fluid dynamics software package FLUENT is applied to determine the related problems. A large computational effort is involved for the memory access of the computers and computing time for the simulation of the complex geometries associated with the dense grids. Standard k - ε turbulence model is allowed to predict the three-dimensional flow and the conjugate heat transfer characteristics.

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