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International Conference on Innovative Applied Energy    

E-Proceedings ISBN: 978-1-912532-05-6

St Cross College, University of Oxford, United Kingdom



Heat Transfer-Fluid Flow Interaction in Natural Convection around Heated Cylinder and Its Thermal Chimney Effect



Haiteng Ma, Li He and Sham Rane

Dept of Engineering Science, Southwell Laboratory, University of Oxford, United Kingdom


Paper Abstract

Geothermal energy, as one important aspect of clean energy, has a huge potential to fufill human’s energy demand but is still vastly under-utilized. In a novel concept of combined power and water generations (Combi-Gen) system proposed to improve utilization efficiency of geothermal energy, there are two key components: thermal chimney for freshwater production and two-phase flow turbine for power generation. Research in this paper emanates from the development of thermal chimney and extracts several interesting findings related to heat transfer-fluid flow interaction in natural convection.

Natural convection studies for a single horizontal cylinder have been extensively conducted since 1910s but most of them focus on heat transfer side. Flow field of the thermal plume around heated cylinders is still not well understood in open literature, yet quite significant to heat exchanger design. In this paper, heat transfer-fluid flow interaction for natural convection of a single heated cylinder was first investigated. Computational Fluid Dynamics (CFD) simulations were implemented with laminar and different turbulent models and further validated by data in literature. Detailed CFD analysis revealed that as thermal plume develops, its temperature decreases due to heat dissipation into cold atmosphere, but its velocity keeps increasing and the flow finally transits to turbulence due to augmented instability. The driving mechanism behind this interesting phenomena is found to be the buoyancy force exerting work on the thermal plume. Next, thermal chimney used in the combined power and water generation (Combi-Gen) system is designed and analyzed. The thermal chimney was constructed by heated cylinder pipes and the effects of cylinder arrangement (inline, stagger) and its geometric paramters (horizontal and vertical pitch, diameter) on the natural draft performance were investigated. The newly discovered flow phenomena and physics showed capability in guiding the design and optimization of themal chimney. 

Paper Keywords
Combined Power and Water Generation System, Thermal Chimney, Natural Convection, Heat Transfer-Fluid Flow Interaction, Computational Fluid Dynamics.
Corresponding author Biography
Dr. Haiteng Ma is a postdoc researcher at thermofluids institute in University of Oxford. He obtained his PhD degree in thermal and power engineering from Shanghai Jiao Tong University, China (2016) and BS degree in mechanical engineering from Shandong University, China (2011). He then worked as a research engineer at Siemens Corporate Technology, responsible for gas turbine thermal technology development, before joining Oxford. Dr. Ma’s research interests are: heat transfer and fluid mechanics related to power generation, aerospace propulsion and low-carbon technologies.

The International Conference on Innovative Applied Energy (IAPE’18)