Eur. Phys. J. Plus (2016) 131: 430
https://doi.org/10.1140/epjp/i2016-16430-x

Regular Article

Thermal efficiency evaluation of solar rings in tubes

Department of Mechanical Engineering, Babol University of Technology, Babol, Iran

^* e-mail: s.ebrahim.ghasemi@stu.nit.ac.ir

Received: 29 April 2016
Accepted: 10 November 2016
Published online: 16 December 2016

Abstract

In this article, the thermal efficiency of solar rings in tubes is investigated numerically. The effect of the distance between solar rings and the size of the rings on fluid flow and heat transfer are studied. This numerical simulation is implemented by using Computational Fluid Dynamics (CFD). Characteristics of the Nusselt number, friction factor, and thermal performance factor are investigated. The heat transfer fluid is Therminol 55 oil and the analysis is carried out based on the renormalization-group (RNG) k- turbulence model. The computation results show that the Nusselt number is augmented in comparison with the smooth tube, which confirms that the solar ring has a good effect of heat transfer enhancement. Also, by decreasing the distance between solar rings, the heat transfer coefficient increases, but by increasing the inner diameter of the solar rings, the Nusselt number decreases.