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Research Papers: Natural and Mixed Convection

# Heat Transfer and Fluid Flow Characteristics in Supercritical Pressure Water

[+] Author and Article Information
Jeremy Licht

Nuclear Engineering and Engineering Physics, College of Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706jeremyrlicht@gmail.com

Mark Anderson

Nuclear Engineering and Engineering Physics, College of Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706manderson@engr.wisc.edu

Nuclear Engineering and Engineering Physics, College of Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706corradini@engr.wisc.edu

The pseudocritical temperature is defined as the temperature at which, for a given pressure, the fluid exhibits a maximum in its specific heat.

J. Heat Transfer 131(7), 072502 (May 13, 2009) (14 pages) doi:10.1115/1.3090817 History: Received June 03, 2008; Revised December 19, 2008; Published May 13, 2009

## Abstract

A series of integral heat transfer measurements in a square annular flow passage was performed for bulk water temperatures of $175–400°C$ with upward mass velocities of $300 kg/m2 s$ and $1000 kg/m2 s$ and heat fluxes of 0, $200 kW/m2$, and $440 kW/m2$, all at a pressure of 25 MPa. Mean and turbulent velocities measured with a two-component laser Doppler velocimetry system along with simulations using the computational fluid dynamics (CFD) code FLUENT were used to explain the deterioration and enhancement of heat transfer in supercritical pressure water. At low mass velocities, the integral heat transfer measurements exhibited large localized wall temperature spikes that could not be accurately predicted with Nusselt correlations. Detailed mean and turbulent velocities along with FLUENT simulations show that buoyancy effects cause a significant reduction in turbulent quantities at a radial location similar to what is the law of the wall region for isothermal flow. At bulk temperatures near the pseudocritical temperature, high mass velocity integral heat transfer measurements exhibited an enhanced heat transfer with a magnitude dependent on the applied heat flux. Measured mean and turbulent velocities showed no noticeable changes under these conditions. FLUENT simulations show that the integrated effects of specific heat can be used to explain the observed effects. The experimentally measured heat transfer and local velocity data also serve as a database to compare existing CFD models, such as Reynolds-averaged Navier-Stokes (RANS) equations and possibly even large Eddy simulations (LES) and direct numerical simulations (DNS). Ultimately, these measurements will aid in the development of models that can accurately predict heat transfer to supercritical pressure water.

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Copyright © 2009 by American Society of Mechanical Engineers
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## Figures

Figure 4

FLUENT simulations using the enhanced wall function are compared with LDV measurements: (a) linear scaling for view of the bulk and (b) logarithmic scaling for view of the near wall. The solid lines represent simulation; the symbols represent measured data.

Figure 5

FLUENT simulations using the standard wall function are compared with LDV measurements: (a) linear scaling for view of the bulk and (b) logarithmic scaling for view of the near wall. The solid lines represent simulation; the symbols represent measured data.

Figure 6

Uncertainties of the LDV measurements shown in Figs.  45

Figure 7

Experimental data from conditions shown in Table 1 are plotted with empirical lines determined by Jackson and Hall (10) to relate the data to the convection regions

Figure 8

Comparison of high mass velocity data with Nusselt correlation of Jackson (33): (a) wall temperature; (b) heat transfer coefficient

Figure 1

Schematic of the important experimental components: (a) the heat transfer loop, (b) cross section of the flow geometry, (c) top view of the optics table, and (d) cross section of the optical block with an exploded view of the optical measurement region

Figure 2

The two different orientations of the beam pairs used in velocity measurements

Figure 3

Cross-sectional view of the meshing scheme: (a) enhanced wall function and (b) standard wall function

Figure 15

Simulated evolution of the wall temperature and turbulence parameters at different axial positions; spanning the evolution of the deterioration process

Figure 9

Comparison of low mass velocity data with the Nusselt correlation of Jackson (33): (a) wall temperature and (b) heat transfer coefficient

Figure 10

Forced convection results on a linear scale for view of bulk flow. Left figures: Normalized LDV data. Middle figures: Normalized properties simulated with FLUENT . Right figure: Average of measured integral heat transfer coefficient.

Figure 11

Forced convection results on a log scale for view of near wall region. Left figures: Normalized LDV data. Middle figures: Normalized properties simulated with FLUENT . Right figure: Average of measured integral heat transfer coefficient.

Figure 12

Mixed convection results on a log scale for view of near wall region. Left column: Normalized LDV data. Middle column: Estimation of normalized property profiles based on measured Tb and Tw. Right column: Axial wall temperature distribution.

Figure 13

Detailed LDV measurements comparing isothermal and low heat flux conditions at an axial location of 0.5 m for conditions of 175°C, 25 MPa, and 308 kg/m2 s

Figure 14

Comparison of the measured and simulated wall temperature profile exhibiting a relatively small spike in wall temperature

## Errata

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