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The paper summarises the merits and limitations of different methods used to determine the rejection criteria of the primary reformer tubes. It compares the microstructures as obtained on the outer surface of the reformer tubes with that observed in the transverse section in the regions of outer wall, midwall and inner surface. On the basis of these studies coupled with dimensional change measurements, the in situ metallographic technique has been used to monitor the condition of tubes in two reformation units and the tubes had given satisfactory service till the next turnaround as predicted.

This literature review focuses on the study and applications of Computational Fluid Dynamics (CFD) in the field of heat exchangers. It has been observed cfd analysis is a very useful tool in the field of heat exchangers to determine the heat transfer characteristics. Different models available in general purpose commercial CFD tools i.e. standard, realizable, energy model, radiation and k-ε (2eqn.), with velocity-pressure coupling schemes such as SIMPLEC have been adopted to carry out the simulations. The qualities of the solutions obtained from these simulations arewithin the acceptable range with very accurate results. Hence proving CFD as an effective tool for predicting the behavior and performance of a wide variety of heat exchangers.Copy Right, IJAR, 2017,. All rights reserved. …………………………………………………………………………………………………….... Introduction:-Heat exchangers play an important role in the operation of systems such as process industries, power plants and heat recovery units. Its inevitable need has necessitated work on efficient and reliable designs leading towards optimum share in the overall system performance. The Log Mean Temperature Difference (LMTD) and the number of heat transfer units (NTU) method are two methods used for design of heat exchanger. These methods have some limitations i.e. iterative in nature and need of a prototype to implement the design. Due to these reasons, these methods are time consuming as well as uneconomical especially for large scale models. However, economical access to powerful microprocessors has created a way for the evaluation of Computational Fluid Dynamics (CFD). CFD is a science that can help to study fluid flow, heat transfer, chemical reactions etc. by solving mathematical equations using numerical analysis. It is also very helpful in designing a heat exchanger system from scratch and in troubleshooting or optimization of the design. CFD employs a very simple principle of resolving the entire system into small cells or grids and applying governing equations on these discrete elements to find numerical solutions regarding pressure distribution, temperature gradients and flow parameters in a shorter time and at a lower cost, as the required experimental work is reduced.The results obtained with the CFD are of acceptable quality. In the current work, various parameters changes have been done in the design of heat exchangers and their solutions with the help of CFD have been reviewed. This work can serve as a ready reference for application of CFD in design of various types of heat exchangers.