scholarly journals On the relative impact of subgrid-scale modelling and conjugate heat transfer in LES of hot jets in cross-flow over cold plates

2011 ◽  
Vol 67 (10) ◽  
pp. 1321-1340 ◽  
Author(s):  
Y. Hallez ◽  
J.-C. Jouhaud ◽  
T. J. Poinsot
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Relative Impact ◽  
Subgrid Scale ◽  
Scale Modelling ◽  
Cold Plates

Numerical Prediction of Combustor Heatshield Flow and Heat Transfer With Sub-Grid-Scale Modelling of Pedestals

2001 ◽  
Author(s):  
John K. Luff ◽  
James J. McGuirk
Keyword(s):  
Heat Transfer ◽  
Life Prediction ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Flow And Heat Transfer ◽  
Extra Energy ◽  
Scale Modelling ◽  
Heat Transfer Calculation ◽  
Proper Account ◽  
Good Agreement

A goal for computational analysis of combustors is to produce a tool for life prediction. An important part of this will be the prediction of the temperature field in the combustor walls. The complex geometries of combustor components make this a formidable task. In this paper a 3D coupled numerical flow/conjugate heat transfer calculation procedure is presented for a combustor heatshield. Proper account must be taken of the blockage and heat transfer effects of pedestals. A scheme has been developed to account for these effects without resolving the pedestals in the computational grid. Extra sink terms are included in the momentum equations to account for pedestal pressure drop. An extra energy equation is solved to determine the local pedestal temperature and to account for heat transfer between pedestals and fluid. This treatment has been validated against empirical data for arrays of pedestals in ducts with good agreement for friction factor and Nusselt number. The methodology is then applied to a generic heatshield geometry to indicate that a viable computational route has been developed for combustor heatshield analysis.

scholarly journals Conjugate Heat Transfer CFD Predictions of Impingement Jet Array Flat Wall Cooling Aerodynamics With Single Sided Flow Exit

2013 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Significant Feature ◽  
Axial Distance ◽  
Impingement Jet ◽  
The Cross

Conjugate heat transfer CFD studies were undertaken on impingement square jet arrays with self induced crossflow in the impingement gap with a single sided exit. The aim was to understand the aerodynamic interactions that result in the deterioration of heat transfer with axial distance, whereas the addition of duct flow heat transfer would be expected to lead to an increase in heat transfer with axial distance. A square array of impingement holes was investigated for a common geometry investigated experimentally, pitch to diameter ratio X/D of 5 and impingement gap to diameter ratio Z/D of 3.3 for 11 rows of holes in the crossflow direction. A metal duct wall was used as the impingement surface with an applied heat flux of 100kW/m2, which for a gas turbine combustor cooling application operating at steady state with a temperature difference of ∼450K corresponds to a convective heat transfer coefficient of ∼200 W/m2K. A key feature of the predicted aerodynamics was recirculation in the plane of the impingement jets normal to the cross-flow, which produced heating of the impingement jet wall. This reverse flow jet was deflected by the cross flow which had its peak velocity in the plane between the high velocity impingement jets. The cross-flow interaction with the impingement jets reduced the interaction between the jets on the surface, with lower surface turbulence as a result and this reduced the surface convective heat transfer. A significant feature of the predictions was the interaction of the cross-flow aerodynamics with the impingement jet wall and associated heat transfer to that wall. The results showed that the deterioration in heat transfer with axial distance was well predicted, together with predictions of the impingement wall surface temperature gradients.

Conjugate Heat Transfer CFD Predictions of the Surface Averaged Impingement Heat Transfer Coefficients for Impingement Cooling With Backside Cross-Flow

2013 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Reyad A. A. Abdul Hussain ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Square Array ◽  
Velocity Turbulence

A 10 row impingement heat transfer configuration with a single sided exit at the end of the impingement gap was modelled using conjugate heat transfer CFD. The predictions were compared with experimental results for an electrically heated, 6.35mm thick, metal wall of nimonic-75, which was impingement cooled. The geometry investigated was a square array of inline impingement 10 × 10 holes with X/D of 4.66 and Z/D of 3.06, where D = 3.27mm. The use of metal walls enabled the local surface averaged heat transfer coefficient h, to be estimated from an imbedded thermocouple that logged the rate of cooling when the heating was removed. Conjugate heat transfer analysis provided local h values, which were surface averaged for comparison with the measured h. The CFD results also provided velocity, turbulence and Nusselt number distributions on the target and impingement jet surfaces. The aerodynamics data enabled the pressure loss of the system to be predicted, which compared well with experimental measurements. The predicted surface distributions of Nusselt number were similar to the surface turbulence kinetic energy distributions, which demonstrated the importance of turbulence in convective heat transfer. Surface averaged heat transfer coefficients were predicted and are in good agreement with the measurements for five coolant mass flow rates. The predicted and measured results for surface averaged h were similar to measurements of other investigators for similar impingement geometries.

Conjugate Heat Transfer CFD Predictions of Impingement Heat Transfer: Influence of the Number of Holes for a Constant Pitch-to-Diameter Ratio X/D

2014 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Reyad A. A. Abdul Hussain ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Unit Surface Area ◽  
Thermal Gradients ◽  
Hole Density ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Constant Pitch ◽  
The Impact

Conjugate heat transfer CFD studies were undertaken on the influence of the number of impingement holes/unit surface area or hole density n (m−2) for n from 1076 to 26910m−2 at a constant X/D of 4.7, with n varied by varying the hole diameter D from 1.31 to 6.54mm and pitch X varied from 6.1mm to 30.5mm. Square array impingement cooling geometries for the jet holes were used with a 152.4 × 152.4mm experimental wall area. The impingement gap had a single sided exit which generated a cross-flow in the gap. The number of impingement holes N in the cross-flow direction was 5, 10, 15 and 25. A coolant mass flux G of 1.93kg/sm2bar was investigated at a constant impingement gap Z of 10mm (Z/D 1.53–7.65 as n was varied). This high coolant mass flow simulated the coolant flow for regeneratively cooled combustors using all the combustor air flow to cool the combustor wall prior to entering the low NOx flame stabiliser. The predictions were compared with experimental results for the heat transfer coefficient h, that used the lumped capacitance method. The predictions of the surface averaged h and pressure loss ΔP/P were in good agreement with the measured results. The predictions showed that increasing the number of impingement jet holes resulted in lower h, due to the impact of cross-flow for large numbers of holes. At the other extreme, a very small number of holes were predicted to have high thermal gradients. The maximum heat transfer was found experimentally and computationally to be 4306 holes per m2 for an X/D of 4.7, with acceptable thermal gradients.

Effect of Inter-Connector on Thermo-Hydraulic Characteristics of Parallel and Counter Flow Mini-Channel Heat Sink

2018 ◽  
Author(s):  
Amitav Tikadar ◽  
Saad K. Oudah ◽  
Azzam S. Salman ◽  
A. K. M. M. Morshed ◽  
Titan C. Paul ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Conjugate Heat Transfer ◽  
Single Phase ◽  
Three Dimensional ◽  
Cross Flow ◽  
Constant Heat Flux ◽  
Hydraulic Characteristics ◽  
Counter Flow ◽  
Flow And Heat Transfer

A numerical investigation of three-dimensional conjugate heat transfer was performed to quantify the thermal and hydraulic performance of an inter-connected parallel and counter flow mini-channel heat sink under laminar flow condition and within the single-phase regime. The aspect ratio (height/width) and the hydraulic diameter of the mini-channel were 0.33 and 750μm respectively. Three different widths of the inter-connector were selected to analyze the effect of cross flow for Reynolds number ranging from 150 to 1044, at a constant heat flux (20 W/cm2). To understand the fluid flow and heat transfer mechanism inside the inter-connector and their effects on overall thermal performance of the heat sink, Nusselt number (Nu), friction factor, pumping power, and overall thermal resistance were analyzed. Results show that the inter-connector has significantly higher effect on counter flow mini-channel heat sink than parallel flow mini-channel heat sink.

Effusion Cooling With Backside Crossflow Cooling and the Backside Coolant Mass Flow Rate Greater Than the Effusion Cooling Mass Flow

2013 ◽  
Author(s):  
G. E. Andrews ◽  
I. M. Khalifa
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Leading Edge ◽  
Duct Flow ◽  
Low Velocity ◽  
Mean Velocity

Full coverage effusion cooling was studied for a square array of 90° effusion cooling holes with backside cooling using a 5 mm depth duct air supply to the coolant holes, with the duct air mass flow rate being greater than the effusion cooling flow. This geometry represents combustor primary zone wall cooling with the dilution air or main combustion air comprising the excess backside flow rate. Active cooling was used with metal walls and 300K effusion cooling into a 27 m/s mean velocity duct flow at 770K crossflow temperature. The aim was to provide conjugate heat transfer experimental data to validate conjugate heat transfer CFD prediction procedures. The 152 mm square test section had 15 rows of holes The X/D value studied was 11.0, which gives a 3% effusion wall pressure loss at a relatively low effusion coolant mass flow rate. The duct air feed to the holes enhanced the backside cooling of the wall. These results were compared with previous work using a plenum chamber air feed and with a crossflow duct, but with equal cross flow air to effusion air. The increased duct air feed velocity relative to the plenum low velocity air feed resulted in an increase in the overall cooling effectiveness due to the additional heat transfer by the duct crossflow velocity. This effect was across the whole duct length when there was surplus cross flow air relative to effusion air, without this the enhanced heat transfer was small and confined to the leading edge area.

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