Heat transfer enhancement in a two-dimensional channel with perforated rectangular blocks using multi-layered porous foa
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Heat transfer enhancement in a two‑dimensional channel with perforated rectangular blocks using multi‑layered porous foam Bing Qi1 · Ruizeng Yuan1 Received: 25 February 2020 / Accepted: 21 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Porous media are very useful tools used for energy management. They are used in vast fields such as in solar heat exchangers to enhance heat transfer for building applications or in electronic equipment to facilitate heat removal from hot elements. This work presents a numerical study on the potential of using multi-layered porous covers to cool discrete solid blocks positioned inside in a two-dimensional channel. In the first step, four porous covers with three layers, including Case A (all layers with maximum permeability), Case B (all layers with minimum permeability), Case C (increasing permeability as going to the outside of porous cover), and Case D (decreasing permeability as going to the outside of the porous cover). The configurations are inspected in three Reynolds numbers, including Re = 500, 1000, 1500. The results show that Case A and Case D have better performances as compared to other cases. Case D guides the flow around the first block, located at the upstream, and improves heat transfer, especially at higher Reynolds numbers. Finally, a new case based on Case D and Case A is proposed. This case has 6% and 10% better overall heat transfer than Case A at Re = 1000 and Re = 1500, respectively. As well as, the Nusselt number of Case E is about 180% at Re = 500, 220% at Re = 1000, and 250% greater than the base case where porous cover is not used. Keywords Porous configuration design · Thermal performance · Porous insert · Energy management · Energy saving List of symbols Da Darcy number Cp Specific heat at constant pressure (J kg−1 K−1) F Forchheimer coefficient g Gravitational acceleration (m s−2) h Heat transfer coefficient (W m−2 K) H Channel height (m) k Thermal conductivity (W m−1 K−1) K Permeability (m2) Nu Nusselt number p Pressure (Pa) Pr Prandtl number q Heat flux (W m−2) T Temperature (K) u, v Local velocity components (m s−1) x, y Cartesian coordinates (m)
* Ruizeng Yuan [email protected] 1
Henan Provincial Academy of Building Research, Zhengzhou, China
Greek symbols ε Porosity θ Nondimensional temperature μ Dynamic viscosity (Pa s) ρ Fluid density (kg m−3) Subscripts eff Effective f Fluid in Inlet s Solid w Wall
Introduction Heat transfer management using porous materials has been in the center of attention in recent years. Porous media may be used in building technology as an isolation to save energy [1] or to enhance and facilitate energy transfer [2]. For example, Chen [3] showed that the wet porous plates could be used in the building walls for cooling purposes via evaporation in the porous plates. Also, the opencell porous medium has been widely utilized in different
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engineering applications. Khanafer and Vafai [4] presented a critical review on applications of nanofluids in p
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