CFD ANALYSIS ON SHELL AND COILED TUBE HEAT EXCHANGER FOR HEAT TRANSFER AUGMENTATION DUE TO AIR BUBBLES INJECTION
Prof. O.P Shukla, Bablu Kumar Yadav
Shell and helical coil heat exchanger, Air bubbles injection, NTU, Nusselt number, Effectiveness, Heat transfer coefficient, CFD.
In this work, attempts are made to increase the number of thermal units (NTU) and performance in a horizontal shell and coiled tube heat exchanger via air bubble injection into the shell side of heat exchanger. Besides, exergy loss due to air bubble injection is investigated. Indeed, air bubble injection and bubbles mobility (because of buoyancy force) can intensify the NTU and exergy loss by mixing the thermal boundary layer and increasing the turbulence level of the fluid flow. Air bubbles were injected inside the heat exchanger via a special method and at new different conditions in this work.If an air flow is injected into a liquid fluid, many ambulant air bubbles are formed inside the fluid. Air bubbles move inside the liquid fluid because of the buoyancy force, and the mobility of these air bubbles makes sizable commixture and turbulence inside the fluid.
This mechanism was employed to enhance the heat transfer rate of a horizontal Shell and Helical tube heat exchanger. The main scope of the present work is to clarify the effect of air bubble injection on the heat transfer rate and effectiveness through a horizontal Shell and Helical tube heat exchanger. However it can be used in any other type of heat exchanger. Especially, this method can be expanded as a promising heat transfer improvement technique in automotive cooling system, for instance in radiator which contains of water or other liquid fluid. The ANSYS FLUENT 14.5 has been used for numerical analysis using multiphase- Eulerian and energy. The k-ϵ standard turbulent model has been used. The graph has been plotted for Nusselt number, NTU, effectiveness and overall heat transfer for different diameter of air bubbles. It has been observed that the 0.7mm diameter of air bubbles has best heat transfer.