A finite-volume method for the conjugate heat transfer in film cooling devices

Montomoli, Francesco; Adami, Paolo; Martelli, Francesco

doi:10.1243/09576509jpe640

Cited by 17 publications

(14 citation statements)

References 15 publications

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“…In order to predict the metal temperature accurately, it is important to carry out a conjugate heat transfer (CHT) method, where the thermal field in the fluid and the solid are solved at the same time. There are mainly two methodologies, using a single solvers for fluid and solid region or using ad hoc solver for the solid part (Montomoli et al 2009). In this work a single code is used for fluid and solid domains because it is required by the optimization process.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional fluid topology optimization for heat transfer

Pietropaoli¹,

Montomoli²,

Gaymann³

2018

Struct Multidisc Optim

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In this work, an in house topology optimization (TO) solver is developed to optimize a conjugate heat transfer problem: realizing more complex and efficient coolant systems by minimizing pressure losses and maximizing the heat transfer. The TO method consists in an idealized sedimentation process in which a design variable, in this case impermeability, is iteratively updated across the domain. The optimal solution is the solidified region uniquely defined by the final distribution of impermeability. Due to the geometrical complexity of the optimal solutions obtained, this design method is not always suitable for classic manufacturing methods (molding, stamping....) On the contrary, it can be thought as an approach to better and fully exploit the flexibility offered by additive manufacturing (AM), still often used on old and less efficient design techniques. In the present article, the proposed method is developed using a Lagrangian optimization approach to minimize stagnation pressure dissipation while maximizing heat transfer between fluid and solid region. An impermeability dependent thermal conductivity is included and a smoother operator is adopted to bound thermal diffusivity gradients across solid and fluid. Simulations are performed on a straight squared duct domain. The variability of the results is shown on the basis of different weights of the objective functions. The solver builds automatically three-dimensional structures enhancing the heat transfer level between the walls and the flow through the generation of pairs of counter rotating vortices. This is consistent to solution proposed in literature like v-shaped ribs, even if the geometry generated is more complex and more efficient. It is possible to define the desired level of heat transfer and losses and obtain the closest optimal solution. It is the first time that a conjugate heat transfer optimization problem, with these constraints, has been tackled with this approach for three-dimensional geometries.

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Section: Introductionmentioning

confidence: 99%

Three-dimensional fluid topology optimization for heat transfer

Pietropaoli¹,

Montomoli²,

Gaymann³

2018

Struct Multidisc Optim

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“…The inner O-type grid and outer H-type grid were used to improve the quality of the whole grid considering that the labyrinth seal is connected to the top of the rotor through the interface, and the geometrical shape of the seal determines that it can only use the h-type grid. In the study by [24], the HTC was studied in detail on a blade similar to S2, indicating that the use of a 20-layer grid near the wall surface could meet the requirements of boundary layer capture. In this paper, the near-wall surface was divided into 20 points by the same method.…”

Section: Numerical Solver and Meshmentioning

confidence: 99%

Effect of Tip Clearance on Flow Field and Heat Transfer Characteristics in a Large Meridional Expansion Turbine

et al. 2019

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The large meridional expansion turbine stator leads to complex secondary flows and heat transfer characteristics in the blade endwall region, while the upstream tip clearance leakage flow of the rotor makes it more complex in flow and heat transfer. The influence of the upstream rotor tip clearance on the large meridian expansion stator is worth studying. The flow and heat transfer characteristics of the downstream large meridional expansion turbine stator were studied by comparing the tip leakage flow of 1.5-stage shrouded and unshrouded turbines using a three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solver for viscous turbulent flows. Validation studies were performed to investigate the aerodynamics and heat transfer prediction ability of the shear stress transport (SST) turbulence model. The influence of different tip clearances of the rotor including unshrouded blade heights of 0%, 1% and 5% and a 1% shrouded blade height were investigated through numerical simulation. The results showed that the upper passage vortex separation was more serious and the separation, and attachment point of horseshoe vortex in the pressure side were significantly more advanced than that of non-expansion turbines. The tip leakage vortex obviously increased the negative incidence angle at the downstream inlet. Furthermore, the strength of the high heat transfer zone on the suction surface of the downstream stator was significantly increased, while that of the shrouded rotor decreased.

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“…The CFD simulations have been carried out using an in house CFD solver Hybflow, by Adami et al [15] and Montomoli et al [16] developed at the University of Florence. The spatial discretisation is based on a finite volume approach for hybrid unstructured grids.…”

Section: Cfd Solvermentioning

confidence: 99%

“…A more detailed description of the code can be found in Montomoli et al [16]. The heat transfer Fourier's equation for the solid zone is evaluated through an explicit time marching scheme.…”

Section: Tab 1 Operative Test Matrixmentioning

confidence: 99%

“…In this particular method the stability is not dependent on the Biot number if the temperature at the interface is updated every iteration, as in the present implementation. The conjugate heat transfer capability of the solver has been previously validated [16] using the analytical solution of Luikov for a flat plate [25] and on a film cooled surface (Martiny et al [26]), not shown in this work.…”

Section: Tab 1 Operative Test Matrixmentioning

confidence: 99%

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The benefit of high-conductivity materials in film cooled turbine nozzles

Montomoli

Massini

Yang

et al. 2012

International Journal of Heat and Fluid Flow

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This study presents an experimental and numerical investigation of the beneficial effect of higher conductivity materials in HP turbine nozzles. Most of the literature studies focus on the maximum temperature that a nozzle can withstand, whereas the effect of thermal gradients is often neglected. However thermal gradients have higher influence on the life of the components and they have to be given careful consideration. In this work it is shown that thermal gradients are reduced by using high conductivity materials and, as a consequence, the nozzles life is appreciably increased.A representative film cooled leading edge with an internal impingement plate was studied experimentally at Texas AM University. Two materials were used, namely polycarbonate and stainless steel, in order to highlight the impact of conduction on coolant effectiveness. Numerically conjugate heat transfer simulations have been carried out with an in house solver to analyse in detail the impact of conduction and internal convection. Both experimental and numerical results show that by increasing the conductivity in the solid region, the thermal gradients are strongly reduced. Numerically it is shown that using inserts of nickel-aluminide alloys in nozzles may reduce the thermal gradients from 3 to 4 times if compared to nowadays design.

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A finite-volume method for the conjugate heat transfer in film cooling devices

Cited by 17 publications

References 15 publications

Three-dimensional fluid topology optimization for heat transfer

Three-dimensional fluid topology optimization for heat transfer

Effect of Tip Clearance on Flow Field and Heat Transfer Characteristics in a Large Meridional Expansion Turbine

The benefit of high-conductivity materials in film cooled turbine nozzles

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