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Novel Geometric Improvements to Enhance Internal Convective Heat Transfer

  • Author(s): Al-Sammarraie, Ahmed
  • Advisor(s): Vafai, Kambiz
  • et al.
Creative Commons 'BY-NC' version 4.0 license
Abstract

Enhancing heat transfer in engineering applications utilizing various techniques has been a major theme in thermal management over the past few decades due to the escalating performance requirements of these applications and equipment. Enhancement techniques include, but not limited to, adopting a wide variety of new materials, alloys, fluids, and configuration improvements. In internal forced convection heat transfer applications, for instance, accelerating fluid and having thinner hydrodynamic and thermal boundary layers can boost the heat exchange along the flow field. By means of an effective configuration improvement technique, such as manipulating the conduit shape and profile, this goal can be achieved despite the rise in pressure drop which is a conjugate constraint. The present work aims at utilizing the geometrical improvement concept and the wall profile manipulation to introduce and analyze the flow and heat transfer, employing conventional- and nano-fluids, in innovative convergent pipes and double pipe heat exchangers. The influences of several parameters such as convergence angle, pipe wall profile, volume fraction of nanoparticles, contraction ratio, as well as Reynolds and Prandtl numbers on the thermal and hydraulic performance of these configurations were examined. In general, the findings show a remarkable increment in heat transfer as the convergence angle, Reynolds number, concavity of the convergent pipe wall, volume fraction of nanoparticles, and contraction ratio increase. In the second part of this work, the concave and convex wall profiles of a convergent pipe show a prominent enhancement in heat transfer and a sustainable thermal-hydraulic performance up to 41% and 22.3%, respectively, compared to a straight wall profile. Further, it has been observed that the addressed configuration improvements play a pivotal role in terms of augmenting heat transfer more than employing nanofluids. In the third part of the current work, the convergent double pipe heat exchanger (C-DPHE) offers a prominent and sustainable performance with enhancement in heat transfer up to 32% and thermal-hydraulic performance up to 20% compared to a conventional one. Moreover, another merit of this innovative double pipe heat exchanger is that it is efficient at low Reynolds and high Prandtl numbers, which means that it does not require high operating pumping power. This part of our work furnishes comprehensive information that can be utilized in establishing the optimal operating conditions of the C-DPHE.

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