Rotating metal foam structures for performance enhancement of double-pipe heat exchangers

Abstract

In order to enhance the amount of heat transported in a double-pipe heat exchanger, a compound enhancement is proposed incorporating both active and passive methods. The first one is through introducing secondary flows in the vicinity of the conducting surface using metal foam guiding vanes, which are fixed obliquely and rotating coaxially to trap fluid particles while rotation and then force them to flow over the conducting surface. The other is via covering the conducting surface between the two pipes with a metal foam layer to improve the heat conductance across it. This proposal is examined numerically by studying the three-dimensional, steady, incompressible, and laminar convective fluid flow in a counter-flow double-pipe heat exchanger partially filled with high porosity metal foam and rotating coaxially. With regards to the influence of rotation, both the centrifugal buoyancy and Coriolis forces are considered in the current study. The generalised model is used to mathematically simulate the momentum equations in the porous regions. Moreover, thermal dispersion has been taken into account while considering that fluid and solid phases are in a local thermal non-equilibrium. Computations are performed for a wide range of design parameters influencing the performance achieved such as the operating conditions, the configuration of the guiding vanes utilized, and the geometrical and thermal characteristics of the metal foam utilised. The results are presented by means of the heat exchanger effectiveness, pressure drop, and the overall system performance. The current proposed design has effectively proved its potential to enhance the heat transported considerably in view of the significant savings in the pumping power required compared to the heat exchangers fully filled with metal foams. Furthermore, the data obtained reveal an obvious impact of the design parameters inspected on both the heat exchanged and the pressure loss; and hence, the overall performance obtained. Although the heat exchanger effectiveness can be improved considerably by manipulating the design factors, care must be taken to avoid unnecessary expenses resulted from potential increases in pressure drop. KEYWORDS: Heat Exchanger, Compound Enhancement, Metal Foams, Rotation, Overall PerformanceNomenclature asf solid-to-fluid interfacial specific surface area cp specific heat of fluid phase Cc cold stream heat-capacity rate Cc = ṁc cp,c Ch cold stream heat-capacity rate Ch = ṁh cp,h Cmin the smaller of the hot (Ch) and the cold (Cc) fluid-phase heat-capacity rates df fiber diameter dp pore diameter Da Darcy number, Da=K / Dh 2 Dh hydraulic diameter of the channel Di1, Di2 internal and external diameters of the inner annular tube Do1, Do2 internal and external diameters of the outer annular tube F inertial coefficient hsf solid-to-fluid interfacial specific heat transfer coefficient Hsf dimensionless solid-to-fluid interfacial specific heat transfer coefficient k thermal conductivity K permeability of the porous medium

High-Porosity Metal Foams: Potentials, Applications, and Formulations

“…Furthermore, Chen et al [20] observed that despite the increase occurred in the pressure drop, using metal foams results in a remarkable heat transfer enhancement (by as much as 11 times), which leads to a considerable improvement in the comprehensive performance, that is, up to 700%. More recently, an innovative double-pipe heat exchanger was proposed [21,22] through using rotating metal foam guiding vanes fixed obliquely to force fluid particles to flow over the conducting surface while rotation. Furthermore, the conducting surface itself was covered with a metal foam layer to improve the heat conductance across it.…”

“…To optimize the performance achieved, an overall performance system factor, that is, OSP, was introduced as the ratio of the heat exchanged to the total pumping power required. Overall, the negligibly small pumping power required compared to the amount of heat exchanged makes the overall performance of such heat exchangers incomparable, that is, OSP = O( 10 2 )( Figure 3) (Alhusseny et al [22]). It was also observed that while increasing the temperature difference from 30 to 300 C, the overall performance achieved can be improved up to 200-300% depending on the Re* value.…”

Graphite Foam Structures as an Effective Means to Cool High-Performance Electronics

“…Such unique hydrothermal features are already in the DNA of either open-core foams formed from highly conductive materials such as metal-or graphite foams (Alhusseny, Al-Fatlawi, et al, 2021). Open-cell metal foams have, for instance, been successfully employed in diversity of thermal applications including heat exchangers (Alhusseny, Turan and Nasser, 2017), latent heat thermal energy storage units (Alhusseny et al, 2020), and the cooling of turbine blades (Al-Aabidy, as well as electrical generators (Alhusseny et al, 2015). On the other hand, the ORNL graphite foams that predominantly possess spherical pores have the potentials to fulfil most of the above-mentioned requirements desirable in thermal management applications .…”

Numerical Study on Thermal and Fluid Dynamic Behavior of a Compact Heat Exchanger Partially Filled with Metal Foam

“…Alhusseny et al [16] investigated numerically a double-pipe heat exchanger partially filled with high porosity metal foam and rotating coaxially. The heat transfer improvement was obtained by an active method and a passive method.…”