Record:   Prev Next
作者 Licht, Jeremy R
書名 Heat transfer and fluid flow characteristics in supercritical water
國際標準書號 9780549804574
book jacket
說明 218 p
附註 Source: Dissertation Abstracts International, Volume: 69-09, Section: B, page: 5750
Advisers: Michael Corradini; Mark Anderson
Thesis (Ph.D.)--The University of Wisconsin - Madison, 2008
A series of integral heat transfer measurements in circular and square annular flow passages were performed for bulk water temperatures of 175-400°C with upward mass velocities of 300-1400 kg/m2s and heat fluxes up to 1.0 MW/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 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. The buoyancy criterion GrbRe 2.7b<10-5 was found to conservatively capture data exhibiting deterioration in heat transfer. Detailed mean and turbulent velocities along with FLUENT simulations show that buoyancy causes a reduction in the turbulent diffusivity of momentum causing the wall and near wall fluid to increase in temperature. As this occurs, the developing velocity gradient profile continually improves the turbulent diffusion from the outer region toward the heated wall. Due to the evolution of the velocity profile, the deterioration process starts again, explaining the oscillatory shape of the axial wall temperature profile
At bulk temperatures near the pseudocritical temperature, high mass velocity integral heat transfer measurements exhibited an enhanced heat transfer that was reduced with increasing 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. Selected Nusselt correlations were compared with data and found to be in general agreement with previous investigators. Jackson's 1979 Nusselt correlation with modifications to include annular heat transfer effects able to capture 95% of all buoyancy free data with an accuracy of 25%
The experimentally measured heat transfer and local velocity data also serves as a database to compare existing CFD models, such as RANS and possibly even LES and DNS simulations. Ultimately, these measurements will aid in the development of models that can accurately predict heat transfer to supercritical pressure water
School code: 0262
Host Item Dissertation Abstracts International 69-09B
主題 Engineering, Mechanical
Engineering, Nuclear
0548
0552
Alt Author The University of Wisconsin - Madison
Record:   Prev Next