**Volume 17, Issue 2, pp 235-245**

**Publication Date**: 2017-06-15

http://dx.doi.org/10.22436/jmcs.017.02.05

M. Hatami - International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xian Jiaotong University, Xian 710049, China.

S. Mosayebidorcheh - Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran.

J. Geng - International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xian Jiaotong University, Xian 710049, China.

D. Jing - International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xian Jiaotong University, Xian 710049, China.

In this paper, hydro-thermally performance of a circular concentric heat pipe is evaluated using the analytical least square method (LSM) and the accuracy of results is examined by fourth order Runge-kutta numerical method. In described problem, the pipe walls are permitted to carry different and opposite slip velocities of nanouids and they are either preserved at constant heat flux of outer wall with the inner wall insulated or vice versa. For this study, five distinct types of nanoparticles: \(Ag, Cu, Cuo, Al_2O_3\) and \(TiO_2\) are considered in the water base fluid and the results of velocity profiles and Nusselt numbers in different slip conditions were presented and discussed. As a main result, by decreasing the distance between the pipes, more heat will transfer to nanofluids from the wall under the heat flux, so it makes larger Nusselt number.

Heat pipe, nanofluid, Nusselt number, LSM.

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