Numerical and experimental investigation of heat transfer behavior in a round tube with the special conical ring inserts

•The CR and DR array of conical turbulator with water as working fluid was studied.•Nu number has different trend in low and high Re number regions.•The conical ring inserts have an unfavorable effect on the heat exchangers efficiency.•The enhancement efficiency calculations imply that DR array is better than CR.

In the present study an experimental investigation was carried out in order to find the role of the conical rings for the heat transfer enhancement and pressure drop change in a pipe with constant heat flux boundary condition. The conical rings were placed in two different arrangements: converging conical ring (CR array) and diverging conical ring (DR array). Also numerical study was performed through Computational Fluid Dynamics (CFD) calculations. The CFD predictions show suitable agreement with the experimental data of Nusselt number but overestimate pressure drop values. The predictions and the experimental results show that in the case of water as working fluid (despite air as working fluid), the conical ring inserts have an unfavorable effect on the enhancement efficiency of the heat-transfer in the heat exchangers.