Nanofluid migration within an absorber pipe of solar unit considering radiation mechanism

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TECHNICAL PAPER

Nanofluid migration within an absorber pipe of solar unit considering radiation mechanism Z. Ebrahimpour1,2 • Seyyed Ali Farshad1,2 • M. Sheikholeslami1,2 Received: 20 July 2020 / Accepted: 13 November 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract To intensify the efficiency, T-shaped fins were utilized inside the tube in current LFR unit. Various configurations of fins with same volume were employed. The carrier fluid is Al2O3-water and turbulent regime was considered. Incorporating DO model and solving pure radiation results in distribution of radiation flux around the tube which is employed as source term in energy equation. Convective transportation with ambient was considered in outer wall. Various inlet temperature and velocity for four cases were examined and outputs were shown in term of plots and contours. Thermal and energy efficiency, irreversibility component and Bejan number were main outputs of this paper. Outputs indicate that selecting Case A leads to obtain the maximum turbulent fluctuation and lowest temperature of outer wall. Replacing Case C instead of A makes temperature of surface to augment about 0.19% while pressure drop decreases about 23.72%. Rise of Re for Case A leads to decrease of Darcy factor about 26%. Highest Nu belongs to Case A and it increases about 79.82% with rise of Re. Lowest values of total irreversibility belongs to case A and growth of Re lead to reduce Sgen,h about 41.88%. Also, this case has minimum value of Be. The highest exergy and thermal efficiency belong to case A. Augment of Tin makes gth to decline about 23.46% while gex augments.

1 Introduction Nowadays, about 85% of the useful energy is generated by fossil fuels (Musa et al. 2018), causing environmental problems and intensive exploitation of fossil fuels. Additionally, the demand of energy has soared in recent decade, which led researchers to use renewable types of energy resources effectively for energy generation. Among different kinds of renewable energies, solar energy is intensively accessible and cost-effective in comparison to other types. LFRs are observed as a technology which can decrease the price in CSP. That was owing to some facts, the supporting parts are usually light, wind impacts are not significant, mirrors are easy to build and narrow, the land need is lower (Zhu et al. 2014; Wang et al. 2019). Generally, two techniques are usually adopted to harness the & M. Sheikholeslami [email protected] 1

Renewable Energy Systems and Nanofluid Applications in Heat Transfer Laboratory, Babol Noshirvani University of Technology, Babol, Iran

2

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

solar energy: solar heat conversion and direct conversion. Between these techniques, the solar heat systems obtained many interest in the procedure industrial uses and many performance increment methods were widely. The heat efficiency of unit should be increased by s