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The never-ending demands of humans have led researchers to find more efficient energy conversion technologies. Enhancing heat transfer rate in a tubular heat exchanger through curved circular rings is one type of passive method that is studied in this work. The computational analysis has been done using "FLUENT" module of ANSYS 16.0. The tubular heat exchanger has internal diameter of 68.1 mm, length of 1.5 m and constant heat flux of 1000 W m −2. Air is the working fluid, which flows in Re varying from 3000 to 21,000. After reaching steady state conditions, the Nusselt number and friction factor are calculated for CCR rings. Furthermore, perforation has been done on these rings with perforation index 8, 12 and 16% and thermo-hydraulic properties are investigated. Computational results show that perforating the rings have a significant effect on heat transfer and friction factor. Greater the perforation index, greater is the Nu and TPF. The maximum enhancements obtained in Nu and TPF are 7.4 and 1.56 times, respectively (as compared to that of smooth tube), for PCCR-16%.

Enhancement of heat exchangers with the usage of inserts which creates turbulence in fluid flow by enhancing heat transfer rate which is an appealing area for researchers to develop efficient and compact heat exchanger with low expenses. Present work deals with computational investigation on circular tube with ϕ� shaped circular ring inserts taken as enhancer for better experience in heat transfer. The geometric dimensions of insert are 68 mm outer diameter with inner ring is half of outer diameter concentric ring having varying DR of 0.8, 0.85 and 0.9 with varying PR 3, 4 & 5 in which hydraulic diameter is 68.1 mm. The length of test section is 1500 mm with 1000 W/m22 of regular heat flux is applied and Re ranges from 3000 to 21000. CFD analysis conducted, compared & results are presented where maximum augmentation of heat transfer could be obtained 5.02–11.21 times simultaneously TPF is 2.14–3.54 times as compared to smooth tube for inserts with DR 0.8 and PR 3 which attained maximum S˙S˙ 3.07–5.1. Keywords: Heat exchanger, thermal performance factor, CFD analysis. Nomenclature