Direct numerical simulation of turbulent supercritical flows with heat transfer

Bae, Jin Ho; Yoo, Jung Yul; Choi, Hyo Geun

doi:10.1063/1.2047588

Cited by 218 publications

(165 citation statements)

References 29 publications

(27 reference statements)

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“…Under most conditions, the contribution of the direct buoyancy production is insignificant and the influence of buoyancy on turbulence is largely via modifying the mean flow (Cotton & Jackson 1990). In addition, DNS also shows that the flow and thermal fields can develop significant dissimilarity under some conditions invaliding the common turbulence modelling approach based on turbulent Prandtl number (Bae et al 2005).…”

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confidence: 99%

“…Satake et al (2000), You, Yoo & Choi (2003) and Bae et al (2006) performed DNS of air flows in a vertical tube, whereas Kasagi & Nishimura (1997) considered a vertical plane channel with a heated and a cooled wall on either side using air-like properties based on the Boussinesq assumption. Bae, Yoo & Choi (2005), Bae, Yoo & McEligot (2008) performed DNS of CO 2 at a supercritical pressure in a vertical circular and annular tube, respectively. Overall the DNS results agree well with the experiments where available, validating the numerical results as well as confirming the trends established from experiments.…”

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confidence: 99%

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Laminarisation of flow at low Reynolds number due to streamwise body force

Seddighi

2016

J. Fluid Mech.

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It is well established that when a turbulent flow is subjected to a non-uniform body force, the turbulence may be significantly suppressed in comparison with that of the flow of the same flow rate and hence the flow is said to be laminarised. This is the situation in buoyancy-aided mixed convection when severe heat transfer deterioration may occur. Here we report results of direct numerical simulations of flow with a linear or a step-change profile of body force. In contrast to the conventional view, we show that applying a body force to a turbulent flow while keeping the pressure force unchanged causes little changes to the key characteristics of the turbulence. In particular, the mixing characteristics of the turbulence represented by the turbulent viscosity remain largely unaffected. The so-called flow laminarisation due to a body force is in effect a reduction in the apparent Reynolds number of the flow, based on an apparent friction velocity associated with only the pressure force of the flow (i.e. excluding the contribution of the body force). The new understanding allows the level of the flow 'laminarisation' and when the full laminarisation occurs to be readily predicted. In terms of the near-wall turbulence structure, the numbers of ejections and sweeps are little influenced by the imposition of the body force, whereas the strength of each event may be enhanced if the coverage of the body force extends significantly away from the wall. The streamwise turbulent stress is usually increased in accordance with the observation of more and stronger elongated streaks, but the wall-normal and the circumferential turbulent stresses are largely unchanged.

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confidence: 99%

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confidence: 99%

Laminarisation of flow at low Reynolds number due to streamwise body force

Seddighi

2016

J. Fluid Mech.

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“…DNS of full compressible Navier-Stokes equation takes an advantage that all compressibility effects can be considered. However, DNS is suffered by the severe time step restriction as addressed in Bae et al (3) . Since the background of this study is development of the supercritical CO 2 domestic heat pump with high efficiency, the temperature range in this DNS is chosen within normal temperature, and forced convective heat transfer is focused by neglecting buoyancy effects.…”

Section: Journal Of Thermal Science and Technologymentioning

confidence: 99%

“…In their DNS, effects of drastic change of Prandtl number and viscosity near the pseudo-critical point are considered under the incompressible assumption where the effects of density variation are neglected. DNS of turbulent CO 2 fluid at supercritical pressure in heated vertical tubes has been performed by Bae et al (3) with low Mach number approximation. In their work, temperature range includes the pseudo-critical region and buoyancy effects on turbulent statistics were investigated.…”

Section: Journal Of Thermal Science and Technologymentioning

confidence: 99%

Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

李新亮

Hashimoto

Tominaga

et al. 2008

JTST

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Direct numerical simulation (DNS) of supercritical CO 2 turbulent channel flow has been performed to investigate the heat transfer mechanism of supercritical fluid. In the present DNS, full compressible Navier-Stokes equations and Peng-Robison state equation are solved. Due to effects of the mean density variation in the wall normal direction, mean velocity in the cooling region becomes high compared with that in the heating region. The mean width between high-and low-speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high Reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilatation of velocity fluctuation can be ignored even for supercritical condition. However, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify fine scale structure and turbulent transport of temperature, which results in high Nusselt number in the cooling condition of the supercritical CO 2 .

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“…Xu et al [7,8] experimentally analyzed the turbulent convective heat transfer of CO2 flowing in a helical pipe at near-critical pressure with a constant heat flux boundary condition, and discussed the effect of inclination angles on the heat transfer of supercritical CO2 in a 0.5 mm diameter tube. Bae et al [9,10] investigated the turbulent heat transfer of CO2 at supercritical pressure flowing in heated vertical tubes using direct numerical simulation (DNS) at the inlet Reynolds numbers of 5400 and 8900. Nemati et al [11] and Peeters [12] studied the turbulent attenuation and the effect of thermal boundary conditions on the development of turbulent pipe flows with fluids at the inlet Reynolds numbers of 360 and 8000.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

Lei

Zhang

et al. 2017

Applied Sciences

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Featured Application: Supercritical carbon dioxide Brayton cycle, geothermal system, nuclear reactor.Abstract: Significant differences in the heat transfer behaviors of supercritical carbon dioxide in a heated channel have been observed at different mass fluxes. At low mass fluxes, a unique heat transfer characteristic is accompanied by a monotonously smooth temperature variation without any temperature peak, even though the ratio of heat flux to mass flux (q/G) is high. In this study, experimental and numerical investigations explore the hidden mechanism of the peculiar heat transfer characteristics of supercritical carbon dioxide at low mass fluxes in vertically upward tubes with inside diameters (ID) of 5 mm. The range of operating conditions examined within the study include a mass flux (G) between 0-200 kg/m 2 s, and a heat flux (q) of up to 120 kW/m 2 . The parametric effects within these experimental conditions were analyzed on the basis of the obtained heat transfer data. Furthermore, a qualitative modeling force analysis and quantitative numerical simulation of vertical flow at low mass flux reveal the heat transfer mechanism for these temperature profiles. In addition, the distribution of flow parameters and thermo-physical properties (such as shear stress, density, and specific heat) in the near-wall region were also studied. It is found that the heat transfer behavior of supercritical CO 2 at low mass flux is similar to "film boiling" at subcritical pressure, where "vapor-like" fluid occupies the sublayer region. Due to reduced buoyancy, the fluid does not cause enough mixing/instability to bring it to the bulk flow.

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Direct numerical simulation of turbulent supercritical flows with heat transfer

Cited by 218 publications

References 29 publications

Laminarisation of flow at low Reynolds number due to streamwise body force

Laminarisation of flow at low Reynolds number due to streamwise body force

Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

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