Flow control and heat transfer enhancement inside a two-dimensional channel using porous blocks and applying bleeding co
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Flow control and heat transfer enhancement inside a two‑dimensional channel using porous blocks and applying bleeding condition between them Rui Hou1 · Peisuo Li2 Received: 24 July 2020 / Accepted: 22 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract There are different methods to enhance forced convective heat transfer. In the current study, porous blocks are used on the hot wall of a two-dimensional channel. Use of porous media can enhance the heat transfer by improving the flow mixing with subsequent increment in the effective thermal conductivity of the domain at the position of the used permeable media. However, a cavity-like flow appears between the blocks, which deteriorates heat transfer there. In this study, a bleeding condition by suction is applied to improve heat transfer there. Effects of some important parameters including porous media permeability, porous blocks relative height, flow Reynolds number, and the bleeding coefficient on the thermal performance and pressure loss are investigated. The outcomes reveal that the bleeding condition effect on heat transfer mainly depends on the bleeding coefficient. For example, the effect of bleeding condition on the total average Nusselt number is negligible for the bleeding coefficient (σ) less than 0.01, while it could improve the average Nusselt number by 36% at σ = 0.05. Furthermore, increasing the permeability of porous blocks, the effect of the bleeding condition becomes more highlighted from the performance number point of view. Keywords Thermal management · Porous media · Suction · Bleeding · Heat transfer enhancement · Forced convection List of symbols A Area (m3) Da Darcy number Cp Specific heat (J kg−1 K−1) F Forchheimer coefficient h Heat transfer coefficient (W m−2 K) H Height of the channel (m) k Thermal conductivity (fluid/porous media) (W m−1 K−1) K Permeability of the porous media (m2) L Total length of the channel (m) Nu Nusselt number p Pressure (pa) PN Performance number Pr Prandtl number (νf/αf) q Heat flux (W m−2) * Peisuo Li [email protected] 1
School of Architectural Engineering and Art Design, Hunan Institute of Technology, Hengyang 421002, Hunan, China
Hunan Technical College of Railway High-speed, Hengyang 421002, Hunan, China
2
Re Reynolds number T Fluid temperature (K) Tb Fluid bulk temperature (K) Tin Inlet temperature (K) Th The hot wall temperature (K) u, v Horizontal and vertical velocity components (m s−2) u0 Inlet velocity (m s−2) W1 Porous blocks width (m) W2 Porous blocks height (m) W3 Porous blocks distance (m) x, y Horizontal and vertical distance (m) Greek symbols ε Porosity μ Dynamic viscosity (Pa s) ρ Density (kg m−3) Subscripts eff Effective f Fluid in Inlet s Solid w Wall
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Introduction Thermal management is one of the concerns of scientists and engineers who are working in the scope of electronic devices, such as supercomputer development. In these devices, the designer is forced to embed hundreds of capacitors, resistors, or
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