An Experimental Investigation of Double Pipe Heat Exchanger Performance and Exergy Analysis Using Air Bubble Injection Technique

To ensure the transfer of thermal energy in high efficiency, a heat exchanger which has the ability to transfer thermal energy in the least time and cost, is used. There are many drawbacks to traditional surface-type heat exchangers, such as the problem of fouling, high resistance to heat transfer to the surface, and increased cost. The technique of air bubble injection is inexpensive, hopeful, and rarely used for improving the heat exchangers' thermal performance. The present article covers heat transfer and exergy analysis even without injecting an air bubble (3 mm in diameter) at the intake of a tube, shell, and tube and shell heat exchanger. The obtained findings indicate that those heat exchangers that injected air bubbles had a higher Nusselt number than heat exchangers that did not inject air bubbles. The technique of bubble injecting through both shell and tube raises the Nusselt number by a factor of between 2.13%-25.18%. The maximum NTU was achieved by injecting an air bubble into both the shell and tube intakes at a Re=15000. Estimated heat transfer improvements associated with injecting air bubbles into the intake of a tube, shell, or both tube and shell are 8.31% and 13.50%, respectively. Compared to the absence of an injected air bubble, the performance increases by 31.8%, 45.1%, and 54.2%, respectively, when the tube, shell, or both the tube and shell are injected with air bubbles.