Effective temperature jump length and influence of axial conduction for thermal transport in superhydrophobic channels

Cowley, A.; Maynes, Daniel; Crockett, Julie

doi:10.1016/j.ijheatmasstransfer.2014.08.033

Cited by 28 publications

(17 citation statements)

References 37 publications

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“…Various studies seek the apparent temperature jump length (or thermal slip length) to describe the macroscopic effect of SH surfaces on thermal transport [34][35][36][37][38]. A larger temperature jump length corresponds to a greater overall convective heat transfer reduction.…”

Section: Introductionmentioning

confidence: 99%

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Inertial effects on thermal transport in superhydrophobic microchannels

Cowley

Maynes

Crockett

2016

International Journal of Heat and Mass Transfer

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This paper presents a numerical investigation on the effects of inertia for laminar fully developed flow in superhydrophobic microchannels where the surface structure consists of a square array of square pillars aligned with the flow direction. Infinite parallel plate channel flow is considered where the flow is assumed to be non-wetting and the meniscus is idealized as flat. A constant heat flux condition is imposed at the tops of the posts whereas the air/liquid interface is assumed to be adiabatic. A wide range of Peclet numbers (1-10000), relative channel spacing sizes (3 orders of magnitude), and solid fractions (0.02-0.9) are considered. The effect of these on friction factor-Reynolds number product, Nusselt number, hydrodynamic slip length and temperature jump length, is explored. Frictional drag and convective heat transfer are reduced for all cases explored. These reductions are greater for small solid fractions, small relative channel sizes, and low Peclet numbers. Interestingly, over a wide range of explored parameters the results correspond well with the analytical diffusion dominated results present in the literature. It is only at the highest Peclet numbers and smallest relative channel sizes that the results deviate significantly from the diffusion dominated Stokes flow scenario. A mapping is presented that illustrates for which parameter ranges the influence of inertia and relative channel size become significant.

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Section: Introductionmentioning

confidence: 99%

“…Several additional studies have investigated the convective heat transfer in SH microchannels [34,35,[45][46][47]. Along with the SH surface structure and thermal boundary condition, several non-dimensional parameters are important in characterizing the thermal transport in SH microchannels.…”

Section: Introductionmentioning

confidence: 99%

Inertial effects on thermal transport in superhydrophobic microchannels

Cowley

Maynes

Crockett

2016

International Journal of Heat and Mass Transfer

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“…whereT s is the temperature of the liquid/solid interface, T c is the average temperature of the composite liquid/solid and air/liquid interface, b t is the temperature jump length, and dT /dn| c is the average temperature gradient normal to the composite interface. A complete description of the temperature jump length can be found in several references and is not discussed in depth here [14][15][16][17]19]. For our purposes, it can be used to estimate the temperature drop associated with the geometry of the SHPo surface structures.…”

Section: Consideration Of the Shpo Surface Geometry Effectsmentioning

confidence: 99%

“…Note that the nucleation in these works is not due to boiling but mass transfer of air. It should be noted that much work has recently been dedicated to the effect that thermally conductive SHPo surface structures can have on the thermal transport of submerged substrates [13][14][15][16][17][18][19][20][21]. However, these studies do not consider mass transfer and focus on how the geometry of the SHPo surface structures affects the heat transfer to the bulk fluid for diffusion dominated (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…However, these studies do not consider mass transfer and focus on how the geometry of the SHPo surface structures affects the heat transfer to the bulk fluid for diffusion dominated (i.e. Stokes flow) [16,19] and convective [13,17,18] microchannel flow scenarios. Essentially the trapped air in the cavities acts as an insulating layer and increases the resistance to heat transfer due to the spreading resistance caused by the surface structure geometry.…”

Section: Introductionmentioning

confidence: 99%

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Influence of micro-structured superhydrophobic surfaces on nucleation and natural convection in a heated pool

Cowley

Maynes

Crockett

et al. 2019

International Journal of Heat and Mass Transfer

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This work experimentally explores sub-boiling pool nucleation on micro-structured superhydrophobic surfaces. All surfaces tested were submerged in a 20 mm deep pool of water and heated from below to maintain a constant surface temperature, while the side walls of the pool were insulated, and the top was covered. Three thermocouples positioned in the pool obtain the average pool temperature. A heat flux sensor is placed directly beneath the surface to measure the heat flux supplied to the pool. Free convection heat transfer coefficients are obtained for the sub-boiling temperature range of 40-90 • C. Six surface types are studied: smooth hydrophilic, smooth hydrophobic, superhydrophobic with rib/cavity structures, superhydrophobic with rib/cavity structures and additional sparsely spaced ribs to close off the cavities, circular posts, and circular holes. It is found that structured superhydrophobic surfaces provide cavities for nucleation to occur. More dissolved air effervesces from the water as the surface temperature increases due to an increased level of supersaturation and convection. The nucleation leads to large air bubble formations that reduce the overall convection coefficient when compared to the smooth surfaces. For the rib/cavity structured surfaces, the bubbles form in an anisotropic manner and are aligned with the surface structure. More bubbles are observed on the superhydrophobic surfaces where the cavities are bounded. Since water's ability to dissolve air is dependent on temperature, heat and mass transfer cannot be treated independently on any of the superhydrophobic surfaces studied here.

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Analytical solution of micro-/nanoscale convective liquid flows in tubes and slits

Kalyoncu

Barışık

2017

Microfluid Nanofluid

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with confinement sizes for no-dissipation cases. In case of non-negligible heat dissipation, viscous heating dominated the Nu value by enhancing the heating while decreasing the heat removal in cooling cases. Implementation of proposed procedure on a micro-channel convection problem from a micro-fluidics application showed the dominant effect of the model defining the slip and jump relationship. Direct use of kinetic gas theory resulted in an increase of Nu by an increase in non-equilibrium, while models developed from published liquid slip and jump values produced an opposite behavior.

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Effective temperature jump length and influence of axial conduction for thermal transport in superhydrophobic channels

Cited by 28 publications

References 37 publications

Inertial effects on thermal transport in superhydrophobic microchannels

Inertial effects on thermal transport in superhydrophobic microchannels

Influence of micro-structured superhydrophobic surfaces on nucleation and natural convection in a heated pool

Analytical solution of micro-/nanoscale convective liquid flows in tubes and slits

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