A new type of boundary condition in convective heat transfer problems

Dorfman, A. Sh.

doi:10.1016/0017-9310(85)90127-9

Cited by 11 publications

(4 citation statements)

References 3 publications

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“…Analytical studies on the laminar flow over a flat plate, which is heated at one side and insulated on the other side, have been carried out by Dorfman [12,13]. His findings highlight the role of temperature head gradients on local heat transfer.…”

Section: Conjugate Heat Transfermentioning

confidence: 99%

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts

2013

Journal of Heat Transfer

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The present study is geared toward quantifying the effects of imposed thermal boundary condition in cooling channel applications. In this regard, tests are conducted in a generic passage, with evenly distributed rib type perturbators at 90deg, with a 30% passage blockage ratio and pitch-to-height ratio of 10. Uniform heat-flux is imposed on the external side of the slab which provides Biot number and solid-to-fluid thermal conductivity ratio around I and 600, respectively. Through infrared thermometiy measurements over the wetted surface and via an energy balance within the solid, conjugate heat transfer coefficients are calculated over a single rib-pitch. The local heat extraction is demonstrated to be a strong function of the conduction effects, observed more dominantly in the rib vicinity. Moreover, the aero-thermal effects are investigated by comparing the flndings with analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. Furthermore, the results are contrasted with the iso-heat-flux wetted boundary condition test case. Neglecting the thermal boundary condition dependence, and thus the true thermal history of the boundary layer, is demonstrated to produce large errors in heat transfer predictions.

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Section: Conjugate Heat Transfermentioning

confidence: 99%

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts

2013

Journal of Heat Transfer

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“…His findings highlight the role of temperature head gradients on local heat transfer. While increasing temperature heads (flow approaches from insulated side) corresponds to augmented heat transfer coefficients, the contrary case of decreasing temperature heads leads to lower than isothermal boundary condition heat transfer [13][14][15]. Moreover, for a surface at a temperature higher than the surrounding fluid, if the wall temperature increases in the flow direction (increasing temperature head), the descended layers of fluid at the adjoining wall come into contact with the increasingly hotter wall, yielding a local temperature augmentation within these layers.…”

Section: Conjugate Heat Transfermentioning

confidence: 99%

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts²

2012

Volume 1: Heat Transfer in Energy Systems; Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer;

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The present study is geared toward quantifying the effects of imposed thermal boundary condition in cooling channel applications. In this regard, tests are conducted in a generic passage, with evenly distributed rib type perturbators at 90 deg, with a 30% passage blockage ratio and pitch-to-height ratio of 10. Uniform heat-flux is imposed on the external side of the slab which provides Biot number and solid-to-fluid thermal conductivity ratio around 1 and 600, respectively. Through infrared thermometry measurements over the wetted surface and via an energy balance within the solid, conjugate heat transfer coefficients are calculated over a single rib-pitch. The local heat extraction is demonstrated to be a strong function of the conduction effects, observed more dominantly in the rib vicinity. Moreover, the aero-thermal effects are investigated by comparing the findings with analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. Furthermore, the results are contrasted with the iso-heat-flux wetted boundary condition test case. Neglecting the thermal boundary condition dependence, and thus the true thermal history of the boundary layer, is demonstrated to produce large errors in heat transfer predictions.

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“…In convection problems, the generally unknown temperature and heat-flux distributions at the solid-fluid interface was coined by Perelman [10] as conjugated heat transfer. Fundamental analytical studies of the laminar flow over a heated flat plate were carried out by Dorfman [11,12]. The findings highlighted the role of the streamwise temperature gradients on the local heat transfer; whereas increasing the temperature head resulted in augmented heat transfer coefficients, the contrary case of decreasing the temperature head led to a lower than isothermal boundary condition heat transfer [12][13][14].…”

Section: B Conjugate Heat Transfermentioning

confidence: 99%

“…Fundamental analytical studies of the laminar flow over a heated flat plate were carried out by Dorfman [11,12]. The findings highlighted the role of the streamwise temperature gradients on the local heat transfer; whereas increasing the temperature head resulted in augmented heat transfer coefficients, the contrary case of decreasing the temperature head led to a lower than isothermal boundary condition heat transfer [12][13][14]. In similar numerical studies on laminar flow inside a circular tube [15,16], when the interface boundary condition was switched from isoheat flux (convective) to conjugate, the results indicated a global Nusselt number reduction of up to 10% [16].…”

Section: B Conjugate Heat Transfermentioning

confidence: 99%

Conjugate Jet Impingement Heat Transfer Investigation via Transient Thermography Method

Cukurel

Fénot

Arts

2015

Journal of Thermophysics and Heat Transfer

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Investigating the conduction-convection coupling, the present study is focused upon measurement of conjugate heat transfer ensuing jet impingement on a 15-mm-thick metallic plate. Based on a rapid change in jet temperature and using time-accurate infrared thermography, a transient measurement methodology is developed toward acquisition of heat transfer coefficients. The new technique is shown to have comparable levels of Nusselt number and effectiveness accuracy, all while significantly reducing the number of consecutive measurements and their duration. To highlight the significance of the conjugate effect, different plate materials (copper, steel, and Inconel) are employed to differ the solid thermal conductivities, resulting in Biot-number variations. The plate surface heat transfer is studied at two injection Reynolds numbers (34,000 and 37,000) and for two nozzle-to-plate distances (two and five jet diameters). The changes in slab material conductivity reveal small but quantifiable differences in heat transfer coefficients (up to ∼20% locally and 9% globally). Furthermore, constituting an upper bound and lower bound, respectively, it is observed that all conjugate Nusselt number distributions lay within the two limits of isoheat flux and isothermal boundary condition cases. NomenclatureBi = he∕λ solid , Biot number Br = e∕xK −1 Pe 1∕3 , Brun number C = heat capacity, J · kg −1 · K −1 D = jet diameter, m E = impingement plate thickness, m H = heat transfer coefficient on the impinging side, W · m −2 · K −1 H = jet exit to impingement plate distance, m h lat = heat transfer coefficient on the lateral side of the slab, W · m −2 · K −1 K = λ solid ∕∕λ air Nu = hD∕λ air , Nusselt number Nu 0 = Nusselt number at the impingement point Pe = Pr × Re, Peclet number Pe = conjugate Peclet number, K −1 · Pe 1∕3 Pr = Prandtl number R = impingement plate radius, m Re = ρVD∕μ, jet Reynolds number r = radial coordinate, m T aw = adiabatic wall temperature, K T j = injection jet temperature, K T ref = T aw , reference temperature in Newton's law of cooling, K T w = impinging side wall temperature, K T w0 = impinging point wall temperature, K T ∞ = ambient temperature, K= thermal conductivity, W · m −1 · K −1 μ air = air dynamic viscosity, N · s · m −2 ρ = density, kg · m −3 φ co = convective heat-flux density of the impingement plate, W · m −2 φ elec = electrical flux density dissipated by Joule effect, W · m −2

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A new type of boundary condition in convective heat transfer problems

Cited by 11 publications

References 3 publications

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Conjugate Jet Impingement Heat Transfer Investigation via Transient Thermography Method

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