Understanding the Dynamic and Static Thermal Transfer in Brick Walls

2012 ◽  
Vol 512-515 ◽  
pp. 2834-2837 ◽  
Author(s):  
Emilio Sassine ◽  
Zohir Younsi ◽  
Yassine Chérif ◽  
Emmanuel Antczak
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Thermal Insulation ◽  
Brick Wall ◽  
Equivalent Resistance ◽  
Thermal Transfer ◽  
Electrical Analogy ◽  
State Case

The aim of this paper is to study the thermal heat transfer through a 33 cm brick wall, typical of old houses in Lille, a northern French town. First, the wall was studied in a steady state case in order to determine its equivalent resistance using the electrical analogy. Then, the wall is replaced by an equivalent homogeneous wall in order to compare the 1D and the 3D thermal transfer. The results show a perfect consistency between the two models, representing a big advantage when other layers are added to the model like thermal insulation and facing.

scholarly journals Proposal for Cryogenic Deburring Equipment’s Design and Thermal Insulation

2019 ◽  
Vol 299 ◽  
pp. 01013
Author(s):  
Rares Campean ◽  
Liana Hancu
Keyword(s):  
Heat Transfer ◽  
Liquid Nitrogen ◽  
Polyurethane Foam ◽  
Thermal Insulation ◽  
Production Capacity ◽  
Insulating Layer ◽  
Thermal Transfer ◽  
Plastic Parts ◽  
Cryogenic Conditions

In the paper are presented elements of the deburring technology of rubber or plastic parts in cryogenic conditions. There is a proposal for deburring equipment that follows: simplicity in use, increased production capacity and reduced consumption of liquid nitrogen. The heat transfer through the insulating layer is calculated using several types of thermal insulation: perlite powder, spray-on polyurethane foam and aerogel blanket. The obtained results are used for the design of a cryogenic deburring equipment where the thermal transfer is minimal.

PROCESSED STRAW AS EFFECTIVE THERMAL INSULATION FOR BUILDING ENVELOPE CONSTRUCTIONS

2012 ◽  
Vol 4 (3) ◽  
pp. 96-103 ◽  
Author(s):  
Jolanta Vėjelienė
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Building Envelope ◽  
Gas Content ◽  
Barley Straw ◽  
Conductivity Measurements ◽  
Insulation Materials ◽  
Thermal Transfer ◽  
The Impact

The efficiency of thermal insulation materials obtained from renewable resources depends on the possibilities of reducing thermal transfer via solid and gaseous conduction, thermal radiation and, in some cases, convection. The heat transfer mechanism for thermal insulation materials mostly depends on the structure and density of the material used. Efficient thermal insulation materials consist of a gaseous phase and a solid skeleton. Gas content in such materials can take more than 99% of material by volume. In this case, thermal transfer via solid conductivity is negligible. The current work analyses the possibilities of reducing heat transfer in the straw of a varying structure. For conducting experiments, barley straw was used. To evaluate the impact of straw stalk orientation in a specimen on thermal conductivity, strongly horizontally and vertically oriented specimens of straw stalks were prepared. To reduce heat transfer via gaseous conduction and convection in large cavities in straw stalks and between stalks, barley straw were chopped and defibered. In order to decrease heat transfer via radiation after thermal conductivity measurements, mechanically processed straw were coated with infrared absorbers. Due to thermal conductivity measurements of chopped and defibered straw, an optimal amount of infrared absorbers were determined.

Impact of Rotor–Stator Interaction on Turbine Blade Film Cooling

1996 ◽  
Vol 118 (1) ◽  
pp. 123-133 ◽  
Author(s):  
R. S. Abhari
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Film Cooling ◽  
Numerical Code ◽  
Test Facility ◽  
Time Resolved ◽  
Injection Model ◽  
Rotor Stator Interaction ◽  
The Impact ◽  
State Case

The goal of this study is to quantify the impact of rotor–stator interaction on surface heat transfer of film cooled turbine blades. In Section I, a steady-state injection model of the film cooling is incorporated into a two-dimensional, thin shear layer, multiblade row CFD code. This injection model accounts for the penetration and spreading of the coolant jet, as well as the entrainment of the boundary layer fluid by the coolant. The code is validated, in the steady state, by comparing its predictions to data from a blade tested in linear cascade. In Section II, time-resolved film cooled turbine rotor heat transfer measurements are compared with numerical predictions. Data were taken on a fully film cooled blade in a transonic, high pressure ratio, single-stage turbine in a short duration turbine test facility, which simulates full-engine nondimensional conditions. Film cooled heat flux on the pressure surface is predicted to be as much as a factor of two higher in the time average of the unsteady calculations compared to the steady-state case. Time-resolved film cooled heat transfer comparison of data to prediction at two spanwise positions is used to validate the numerical code. The unsteady stator–rotor interaction results in the pulsation of the coolant injection flow out of the film holes with large-scale fluctuations. The combination of pulsating coolant flow and the interaction of the coolant with this unsteady external flow is shown to lower the local pressure side adiabatic film effectiveness by as much as 64 percent when compared to the steady-state case.

A Numerical Investigation of the Effect of Inlet Velocity Oscillation on Heat Transfer in a Two-Dimensional Laminar Jet Impinging on an Isothermal Surface

2016 ◽  
Author(s):  
Johnny Issa ◽  
Najib Saliba ◽  
Bchara Sidnawi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Steady State ◽  
Strouhal Number ◽  
Average Nusselt Number ◽  
Inlet Velocity ◽  
Isothermal Surface ◽  
The Right ◽  
State Case

Heat transfer in a laminar confined oscillating slot jet impinging on an isothermal surface is numerically investigated. A uniform inlet velocity profile, oscillating with an angle φ, is used at the jet exit. The angle φ changes in a sinusoidal form. The height-to-jet width ratio is fixed at 5. The working fluid is air with constant physical properties corresponding to Prandtl number, Pr, equal to 0.74 at ambient conditions. Reynolds number, Re, is defined based on the jet hydraulic diameter and is varied in the self-stable range between 100 and 400. Strouhal number, St, is also varied between 0.05 and 0.75. Oscillating the jet at Reynolds number equal to 100 showed no heat transfer improvement over the steady state case, regardless of the used Strouhal number values. The vortices generated by the oscillation were too weak and could barely reach the wall. The flow showed a high vulnerability to severe oscillations which drastically reduced the jet heat removal ability. The vorticity contours showed a perfect symmetry which resulted in instantaneous and average Nusselt number distributions that are symmetric about the center of the isothermal surface at x = 0. The average stagnation Nusselt number, Nu0, decreased by about 1.25% as Strouhal number is increased from 0.4 to 0.625 then dipped by 44.1% as St is further increased to 0.75, a fact that was attributed to reduction in the bulk momentum by the relatively high frequency. With Reynolds number at 250, the lowest two frequencies corresponding to St of 0.05 and 0.1, resulted in a flow field that is more developed to the right side of the channel, a phenomenon that was linked to the direction of the first jet swing. The corresponding average Nusselt number distributions were consequently asymmetric, with a significant shift to the right. This asymmetric behavior gradually disappeared as the frequency is increased. At St of 0.4 and 0.5, the average stagnation Nusselt number Nu0, showed a 2.2% increase over the steady jet case. As Strouhal number is further increased beyond 0.5, the average Nu0 gradually decreased, since the oscillation period became too short for a vortex to be strong enough to reach the wall. For Reynolds number set at 400, the oscillating condition at the inlet engaged the jet into flapping. The jet showed a tendency to a permanent lean towards one side of the channel, for all used frequencies. Flapping was more one-sided which led to a shift in the average Nusselt number distribution at low frequencies. As Strouhal number is increased to 0.75, flapping became more stable and the generated vortices were expectedly weaker due to the higher frequency. Also, at this Strouhal number value, the average Nu distribution showed the best symmetry with a 2.45% improvement of the average stagnation Nusselt number, over that of the steady state case.

An Investigation of the Effect of interrupted fin arrangements on the Thermal Performance of a Heat Sink under a Free Convection Condition

2019 ◽  
Vol 7 (1) ◽  
pp. 43-53
Author(s):  
Abbas Jassem Jubear ◽  
Ali Hameed Abd
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Thermal Performance ◽  
Heat Sink ◽  
Numerical Study ◽  
Ansys Fluent ◽  
Fluent Software ◽  
Steady State Heat ◽  
Steady State Heat Transfer

The heat sink with vertically rectangular interrupted fins was investigated numerically in a natural convection field, with steady-state heat transfer. A numerical study has been conducted using ANSYS Fluent software (R16.1) in order to develop a 3-D numerical model.  The dimensions of the fins are (305 mm length, 100 mm width, 17 mm height, and 9.5 mm space between fins. The number of fins used on the surface is eight. In this study, the heat input was used as follows: 20, 40, 60, 80, 100, and 120 watts. This study focused on interrupted rectangular fins with a different arrangement and angle of the fins. Results show that the addition of interruption in fins in various arrangements will improve the thermal performance of the heat sink, and through the results, a better interruption rate as an equation can be obtained.

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