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research-article

Numerical investigation of thermal separators within the evacuated tubes of a water-in-glass solar water heater

[+] Author and Article Information
Asif Soopee

Mechanical and Production Engineering Department, Faculty of Engineering, University of Mauritius
amsoopee@gmail.com

Abdel Anwar Hossen Khoodaruth

Senior Lecturer Mechanical and Production Engineering Department, Faculty of Engineering, University of Mauritius
a.khoodaruth@uom.ac.mu

Anshu Prakash Murdan

Lecturer Electrical and Electronic Engineering Department, Faculty of Engineering, University of Mauritius
a.murdan@uom.ac.mu

Vishwamitra Oree

Lecturer Electrical and Electronic Engineering Department, Faculty of Engineering, University of Mauritius
v.oree@uom.ac.mu

1Corresponding author.

ASME doi:10.1115/1.4040758 History: Received April 14, 2018; Revised June 26, 2018

Abstract

The effects of thermal separators within the evacuated tubes of a water-in-glass solar water heater (SWH) were numerically investigated using the commercial Computational Fluid Dynamics (CFD) software ANSYS Fluent. To validate the 3D model, an experiment was performed for the passive operation of the SWH for a fortnight period, of which 3 hours of recorded data was selected. The Boussinesq's approximation was employed and the respective solar irradiance and ambient temperature profiles incorporated. A maximum deviation of only 2.06% was observed between the experimental and numerical results. The model was then adapted for the case where thermal separators are inserted within the evacuated tubes of the SWH and both cases were run for two tilt angles, 10o and 40o. The temperature and velocity profiles within the evacuated tubes were analyzed alongside the temperature contours, thermal stratification, and overall thermal efficiency of the SWH. At a 40o tilt, without thermal separators, the flow streams within the evacuated tubes are restrained and a chaotic thermal behavior was observed, thereby restricting thermal distribution to the water stored in the SWH tank. A lower tilt angle (10o) provided a more desirable thermal distribution. With thermal separators, however, the tilt angle preference was reversed. A faster and more uniform thermal distribution within the water tank, with a sizeable reduction in thermal stratification at 40o tilt. The overall thermal efficiency of the SWH was improved by 8.22% and 8.28% for tilt angles of 10o and 40o, respectively.

Copyright (c) 2018 by ASME
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