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One of the ways to improve heat transfer efficiency is to use a spiral structure for tubes instead of conventional direct tubes. Compared to the direct tubes, spiral tubes have a more compact surface and have higher heat transfer and friction coefficients. When the fluid flows through the spiral tubes, it influences by the centrifugal force which this centrifugal force creates a secondary flow in the fluid, and as a result, this secondary flow increases the axial flow velocity near the outer wall of the tube. Thereby increasing the axial velocity will reduce the thermal resistance and

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Air-cooled heat exchangers are utilized in various industries to cool process fluids. To have a better heat transfer, fins are used in the structure of exchangers. In this study, a set of experiments were performed to investigate the improvement in the amount of heat transfer in an air-cooled heat exchanger. For this purpose, a real case study was conducted on air-coolers in a natural gas compressor station; afterward, the finned tubes were replaced by pulsating heat pipes (PHPs), and a different type of fluid was applied to the pulsating heat pipes. The laboratory system was set up to measure the overall heat transfer coefficient under two conditions involving either finned tubes or a PHP with R134, R22, and filled acetone fluids. Finally, the results were verified by the theory method. The results showed that all the three fluid agents (R134, R22, and Acetone) with natural convection of 9.94 m/s, an inlet fluid velocity of 5.54 m/s, and an average feed velocity were able to enhance the heat transfer coefficient by 10, 13, and 11%, respectively. In addition, compared with finned tubes, R134, R22, and Acetone improved the natural convection heat transfer coefficient by 22.2, 18.6, and 21.7%, respectively.