Heat Transfer and Temperature Field Experiments in a Cavity With Rotation, Recirculation, and Coolant Throughflow

1975 ◽  
Vol 97 (1) ◽  
pp. 22-28 ◽  
Author(s):  
E. M. Sparrow ◽  
T. C. Buszkiewicz ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Field Experiments ◽  
Rotating Disk ◽  
Separation Distance ◽  
The Other ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Annular Gap ◽  
Isothermal Fluid

Local wall heat transfer coefficients and fluid temperature distributions were measured in a cavity consisting of a pair of parallel disks and a cylindrical shroud. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air entered the cavity through a central aperture in the rotating disk and exited through an annular gap at the rim of the rotating disk. The coolant flow rate, the disk rotational speed, and the cavity aspect ratio (disk separation distance to radius) were varied throughout the course of the experiments. The latter parameter took on values as large as two. The heat transfer results and the fluid isotherm maps suggested that the flow pattern within the cavity was markedly different depending upon whether the coolant stream or the pumping action of the rotating disk was predominant. The surface distributions of the heat transfer coefficients reversed the direction of their spatial variation over the range from no rotation to high rotation. However, the maximum values of the Nusselt number curves for no rotation were as high as the maximum values of the curves for corresponding cases with high rotation. The isotherm maps for the no-rotation cases revealed that the major portion of the cavity was filled with nearly isothermal fluid. On the other hand, in the presence of strong rotation, there were substantial fluid temperature variations throughout the cavity.

scholarly journals Heat Transfer Boundary Conditions in the RELAP5-3D Code

2008 ◽  
Author(s):  
Richard A. Riemke ◽  
Cliff B. Davis ◽  
Richard R. Schultz
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Surface Temperature ◽  
Volume Fraction ◽  
Control Variable ◽  
Time Dependent ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
General Table

The heat transfer boundary conditions used in the RELAP5-3D computer program have evolved over the years. Currently, RELAP5-3D has the following options for the heat transfer boundary conditions: (a) heat transfer correlation package option, (b) non-convective option (from radiation/conduction enclosure model or symmetry/insulated conditions), and (c) other options (setting the surface temperature to a volume fraction averaged fluid temperature of the boundary volume, obtaining the surface temperature from a control variable, obtaining the surface temperature from a time-dependent general table, obtaining the heat flux from a time-dependent general table, or obtaining heat transfer coefficients from either a time- or temperature-dependent general table). These options will be discussed, including the more recent ones.

Heat Transfer Model for Condensation in Non-Circular Microchannels

2007 ◽  
Author(s):  
Akhil Agarwal ◽  
Todd M. Bandhauer ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Acute Angle ◽  
Heat Transfer Model ◽  
The Other ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Tube Shape ◽  
Flow Mechanisms ◽  
Circular Microchannels

A model for predicting heat transfer during condensation of refrigerant R134a in horizontal noncircular microchannels is presented. The thermal amplification technique developed and reported in earlier work by the authors is used to measure condensation heat transfer coefficients for six non-circular microchannels (0.424 < Dh < 0.839 mm) of different shapes over the mass flux range 150 < G < 750 kg/m2-s. The channels included barrel-shaped, N-shaped, rectangular, square, and triangular extruded tubes, and a channel with a W-shaped corrugated insert that yielded triangular microchannels. Results from previous work by the authors on condensation flow mechanisms in microchannel geometries were used to interpret the results based on the applicable flow regimes. The effect of tube shape was also considered in deciding the applicable flow regime. A modified version of the annular flow based heat transfer model proposed recently by the authors for circular microchannels, with the required shear stress being calculated from a noncircular microchannel pressure drop model also reported earlier was found to best correlate the present data for square, rectangular and barrel-shaped microchannels. For the other microchannel shapes with sharp acute-angle corners, a mist flow based model from the literature on larger tubes was found to suffice for the prediction of the heat transfer data. These models predict the data significantly better than the other available correlations in the literature.

Experimental and Numerical Investigation of Convection Heat Transfer of CO2 at Supercritical Pressures in a Vertical Mini Tube

2004 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Yi-Jun Xu ◽  
Run-Fu Shi ◽  
S. He
Keyword(s):  
Heat Transfer ◽  
Wall Thickness ◽  
Fluid Pressure ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Fluid Temperature ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Bulk Fluid ◽  
Heat Transfer Coefficients

Convection heat transfer of CO2 at supercritical pressures in a vertical mini tube with a diameter of 0.948 mm was investigated experimentally and numerically. The local heat transfer coefficients, bulk fluid temperatures and wall temperatures were measured and presented. The effects of inlet fluid temperature, fluid pressure, mass flow rate, heat flux and wall thickness on the convection heat transfer in the mini tube were investigated. The experimental results were compared with calculated results using well-known correlations and numerical simulations. The results showed that the variable thermophysical properties of supercritical CO2 significantly influenced the convection heat transfer in the vertical mini tube and that for the studied conditions the influence of the wall thickness on the convection heat transfer in the mini tube was not great. For bulk fluid temperatures higher than the pseudo-critical temperature, the simulation results and the correlation results for the convection heat transfer coefficients in the mini tube corresponded well to the experimentally measured results.

scholarly journals Online Fatigue-Monitoring Models with Consideration of Temperature Dependent Properties and Varying Heat Transfer Coefficients

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
HengLiang Zhang ◽  
Shi Liu ◽  
Danmei Xie ◽  
Yangheng Xiong ◽  
Yanzhi Yu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Stress ◽  
Transfer Coefficient ◽  
Green’S Function ◽  
Green's Function ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Temperature Dependent ◽  
Heat Transfer Coefficients

Thermal stress failure caused by alternating operational loads is the one of important damage mechanisms in the nuclear power plants. To evaluate the thermal stress responses, the Green’s function approach has been generally used. In this paper, a method to consider varying heat transfer coefficients when using the Green’s function method is proposed by using artificial parameter method and superposition principle. Time dependent heat transfer coefficient has been treated by using a modified fluid temperature and a constant heat transfer coefficient. Three-dimensional temperature and stress analyses reflecting entire geometry and heat transfer properties are required to obtain accurate results. An efficient and accurate method is confirmed by comparing its result with corresponding 3D finite element analysis results for a reactor pressure vessel (RPV). From the results, it is found that the temperature dependent material properties and varying heat transfer coefficients can significantly affect the peak stresses and the proposed method can reduce computational efforts with satisfactory accuracy.

Conjugate Heat Transfer in a Rotor-Stator System With Through-Flow

2002 ◽  
Author(s):  
Reby Roy ◽  
B. V. S. S. S. Prasad ◽  
S. Srinivasa Murthy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer Thickness ◽  
Conjugate Heat Transfer ◽  
Rotating Disk ◽  
Thermal Boundary Layer Thickness ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Through Flow

The conjugate heat transfer in a stationary cylindrical cavity with a rotating disk and fluid through-flow is analysed at various rotational speeds ranging from 10000 to 50000 rpm by using a finite volume commercial code. The numerical model and code are validated for a problem, which involves rotation and fluid through-flow. A reduction of the thermal boundary layer thickness and increase in the heat transfer coefficients are observed with increase in the rotational speed. Marked differences are noticed between the Nusselt numbers obtained from the conjugate and constant temperature analyses.

Investigation of Characteristic-Temperature Approaches for Heat-Transfer Correlations at Supercritical Conditions

2013 ◽  
Author(s):  
Sarah Mokry ◽  
Igor Pioro
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Wall Temperature ◽  
Characteristic Temperature ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Supercritical Conditions ◽  
Bulk Fluid ◽  
Heat Transfer Coefficients ◽  
Bare Tube

It is expected that the next generation of water-cooled nuclear reactors will operate at supercritical pressures (∼25 MPa) and high coolant temperatures (350–625°C). In support of the development of SuperCritical Water-cooled Reactors (SCWRs), research is currently being conducted for heat-transfer at supercritical conditions. Currently, there are no experimental datasets for heat transfer from power reactor fuel bundles to the fuel coolant (water) available in open literature. Therefore, for preliminary calculations, heat-transfer correlations obtained with bare-tube data can be used as a conservative approach. A number of empirical generalized correlations, based on experimentally obtained datasets, have been proposed to calculate Heat Transfer Coefficients (HTCs) in forced convective heat transfer for various fluids, including water, at supercritical pressures. These bare-tube-based correlations are available in various literature sources. There have been a number of methods applied to correlate heat transfer data. The most conventional approach, which accounts for property variations in the data, is to modify the classical Dittus-Boelter equation for forced convection. However, analysis and comparison of these correlations has shown that differences in HTC values can be up to several hundred percent. In general, the familiar correlations of Dittus-Boelter and Bishop et al. have used the bulk-fluid temperature approach for characteristic temperature properties evaluations. However, at high heat fluxes, fluid near the tube-wall will have a temperature close to that of the wall temperature. This might be significantly different from the bulk-fluid temperature. Therefore, another approach can be used based on the wall temperature as the characteristic temperature. The Swenson et al. correlation is based upon this approach. Finally, a third approach has been considered in which the film-temperature is used as the characteristic temperature (Tf = (Tw+Tb) / 2). McAdams et al. based their correlation for annuli on this approach. Therefore, the objective of this paper is to evaluate the three characteristic temperature approaches, (1) Bulk-fluid temperature approach; (2) Wall-temperature approach; and (3) Film-temperature approach, and determine which characteristic temperature method can most accurately predict supercritical water heat transfer coefficients. Both classical correlations and more recently developed correlations are considered in this investigation.

A Comparison of the Transient and Heated-Coating Methods for the Measurement of Local Heat Transfer Coefficients on a Pin Fin

1989 ◽  
Vol 111 (4) ◽  
pp. 877-881 ◽  
Author(s):  
J. W. Baughn ◽  
P. T. Ireland ◽  
T. V. Jones ◽  
N. Saniei
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Uniform Heat Flux ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
The Difference

Measurements of the local heat transfer coefficients on a pin fin (i.e., a short cylinder in crossflow) in a duct have been made using two methods, both of which employ liquid crystals to map an isotherm on the surface. The transient method uses the liquid crystal to determine the transient response of the surface temperature to a change in the fluid temperature. The local heat transfer coefficient is determined from the surface response time and the thermal properties of the substrate. The heated-coating method uses an electrically heated coating (vacuum-deposited gold in this case) to provide a uniform heat flux, while the liquid crystal is used to locate an isotherm on the surface. The two methods compare well, especially the value obtained near the center stagnation point of the pin fin where the difference in the thermal boundary condition of the two methods has little effect. They are close but differ somewhat in other regions.

Measured Heat Transfer Coefficients at and Adjacent to the Tip of a Wall-Attached Cylinder in Crossflow—Application to Fins

1981 ◽  
Vol 103 (4) ◽  
pp. 778-784 ◽  
Author(s):  
E. M. Sparrow ◽  
F. Samie
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Visualization ◽  
Cylindrical Surface ◽  
The Other ◽  
Heat Transfer Analysis ◽  
End Effect ◽  
Transfer Coefficients ◽  
End Effects ◽  
Heat Transfer Coefficients

Wind tunnel studies encompassing both heat transfer measurements and flow visualization were performed for a cylinder in crossflow, with one end of the cylinder attached perpendicular to a wall and with the other end free. The focus of the work was to obtain heat transfer coefficients for the tip of the cylinder, for the tip-adjacent portion of the cylindrical surface, and for a portion of the cylindrical surface where there are no end effects. The flow visualization studies were performed to assist in the explanation and rationalization of the heat transfer results. They revealed the presence of spanwise flows adjacent to both ends of the cylinder, with accompanying modifications of the size of the separated region that washes the rear of the cylinder. The flow passing over the tip separates on the fore portion of the tip, but reattaches on the aft portion. The tip heat transfer coefficients are higher than those for the end-effect-free portion of the cylindrical surface, with deviations which grow with increasing Reynolds number (about a factor of two at Re = 25,000). For the tip-adjacent portion of the cylindrical surface, the coefficients are about fifty percent higher than those uninfluenced by end effects. The ramifications of these findings on the heat transfer analysis of fins are discussed.

Heat and Mass Transfer From a Rotating Disk

1959 ◽  
Vol 81 (2) ◽  
pp. 95-103 ◽  
Author(s):  
F. Kreith ◽  
J. H. Taylor ◽  
J. P. Chong
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Rotating Disk ◽  
Heat Transfer Process ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Turbulent Vortex ◽  
Heat Transfer Coefficients ◽  
Adiabatic Surface ◽  
Measured Mass

The analogy between heat, mass, and momentum transfer is applied to a rotating disk. Experimentally measured mass-transfer rates from a disk rotating in an infinite environment under laminar and turbulent conditions are related to the corresponding heat-transfer process by means of an analogy method. The experimental analog is shown to eliminate difficulties associated with accurate measurements of heat-transfer coefficients. Experimental data on the effect of an adiabatic surface placed at various distances parallel to the disk on the transfer rate from the disk are presented. Observations of some unusual flow patterns resulting from Goertler type vortexes in the transition regime and from some as yet unexplained turbulent vortex phenomena are also reported.

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