Stability and Transient Performance of Vertical Heater Vertical Cooler Natural Circulation Loops with Metal Oxide Nanoparticle Suspensions

ABSTRACT

Experimental and theoretical investigations on forced convection have generally indicated superior heat transfer capabilities of nanoparticle suspensions (nanofluids) compared to the corresponding base fluids. However, some studies on natural convection heat transfer in nanofluids have shown negative impacts on heat transfer capabilities, while used in vertical fluid columns. The present investigation is aimed at understanding the heat transfer performance of oxide nanofluids in a rectangular natural circulation loop. The circulation in a natural circulation loop is more or less similar to that in a forced circulation system, but with low velocities. Hence, it is important to observe and quantify the heat transfer behavior of nanofluids in natural circulation loops. In the present work, investigations have been performed on a vertical heater-vertical cooler natural circulation loop, designed to operate stably at all operating conditions considered, based on a linear stability analysis, which was confirmed further using the experimental results. Evaluation of the transient heat transfer performance of the experimental system indicates that aqueous nanofluids containing aluminum oxide and copper oxide have superior heat transfer capabilities in the rectangular natural circulation loop, compared to pure water.

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Notes on contributors

Shijo Thomas

Shijo Thomas is an assistant professor in the School of Nano Science and Technology and adjunct faculty member in the Department of Mechanical Engineering at National Institute of Technology, Calicut. He earned his Master's degree in Thermal Engineering from IIT Madras and Ph.D. from NIT Calicut. His major areas of research are convective heat transfer, nanofluids, CVD synthesis of nanomaterials, adsorption of refrigerants and CO₂ in nanomaterials, biofuel synthesis from waste oils, plastic, tyres, etc. He has co-authored around 19 articles in international journals, conferences and two book chapters.

Choondal B. Sobhan

Choondal B. Sobhan is a professor in the School of Nano Science and Technology and in the Department of Mechanical Engineering, National Institute of Technology, Calicut, India. He earned his Ph.D. in 1990 from Indian Institute of Technology, Madras, and performed postdoctoral research as a visiting scholar at the Cooling Technologies Research Consortium, School of Mechanical Engineering, Purdue University, Indiana, USA. He has been a visiting faculty member at Rensselaer Polytechnic Institute, the University of Colorado–Boulder, and the G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology. His background is in research topics such as heat transfer and flow visualization, microchannels, and micro heat pipes. He has co-authored more than 90 articles in international journals and conferences, and a book, Microscale and Nanoscale Heat Transfer, published by CRC Press.