Yucca Mountain Project Preclosure Ventilation Heat Transfer Analysis: Determining the Mixed Convection Heat Transfer Coefficients

2004 ◽  
Author(s):  
Sandra Dalvit Dunn ◽  
Stephen W. Webb ◽  
Robert Walsh ◽  
Veraun Chipman
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Outer Cylinder ◽  
Convection Heat Transfer ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Transfer Mechanism ◽  
Convection Model ◽  
Experimental Values

Mixed convection is an important heat and mass transfer mechanism in the YMP drifts prior to the repository closure. There is little information in the literature on mixed turbulent convection for a similar horizontal annulus configuration. A model was developed using the Morgan approach, combining forced and natural convection models. A rigorous uncertainty analysis was performed. Comparisons between the mixed convection model and experimental values showed agreement for the inner cylinder. The model consistently under-predicted heat transfer from the outer cylinder. The methodology was later employed in the analysis to predict the heat transfer associated with a full scale ventilated emplacement drift.

Heat Transfer Correlations for Turbulent Mixed Convection in the Entrance Region of a Uniformly Heated Horizontal Tube

2006 ◽  
Vol 128 (10) ◽  
pp. 1103-1107 ◽  
Author(s):  
Walter Grassi ◽  
Daniele Testi
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Cross Sections ◽  
Convection Heat Transfer ◽  
Horizontal Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Developing Flow ◽  
Mixed Convection Heat Transfer ◽  
Heated Length

Flow of perfluorohexane in the entry region of a uniformly heated horizontal cylindrical duct was studied in a regime of weakly turbulent mixed convection. Heat transfer coefficients were measured at five cross sections along the heated length and various values of flow rate and heat flux were imposed. A different thermofluid-dynamic behavior was observed between the upper and lower sides of the pipe. Correlations of the Nusselt number for developed and developing flow were proposed, showing agreement with the experimental data within the 10% deviation band.

scholarly journals Experimental Convection Heat Transfer Analysis of a Nano-Enhanced Industrial Coolant

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 267 ◽  
Author(s):  
Eva Álvarez-Regueiro ◽  
Javier Vallejo ◽  
José Fernández-Seara ◽  
Josefa Fernández ◽  
Luis Lugo
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Heat Transfer Analysis ◽  
Functionalized Graphene ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Cooling Systems ◽  
Graphene Nanoplatelet ◽  
Pressure Drops ◽  
Heat Transfer Coefficients

Convection heat transfer coefficients and pressure drops of four functionalized graphene nanoplatelet nanofluids based on the commercial coolant Havoline® XLC Pre-mixed 50/50 were experimentally determined to assess its thermal performance. The potential heat transfer enhancement produced by nanofluids could play an important role in increasing the efficiency of cooling systems. Particularly in wind power, the increasing size of the wind turbines, up to 10 MW nowadays, requires sophisticated liquid cooling systems to keep the nominal temperature conditions and protect the components from temperature degradation and hazardous environment in off-shore wind parks. The effect of nanoadditive loading, temperature and Reynolds number in convection heat transfer coefficients and pressure drops is discussed. A dimensionless analysis of the results is carried out and empirical correlations for the Nusselt number and Darcy friction factor are proposed. A maximum enhancement in the convection heat transfer coefficient of 7% was found for the nanofluid with nanoadditive loading of 0.25 wt %. Contrarily, no enhancement was found for the nanofluids of higher functionalized graphene nanoplatelet mass fraction.

Natural-Convection Heat Transfer in Liquids Confined by Two Horizontal Plates and Heated From Below

1959 ◽  
Vol 81 (1) ◽  
pp. 24-28 ◽  
Author(s):  
Samuel Globe ◽  
David Dropkin
Keyword(s):  
Heat Transfer ◽  
Silicone Oil ◽  
Convection Heat Transfer ◽  
Test Results ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Silicone Oils ◽  
Prandtl Numbers ◽  
The Relationship ◽  
Rayleigh Numbers

This paper presents results of an experimental investigation of convective heat transfer in liquids placed between two horizontal plates and heated from below. The liquids used were water, silicone oils of 1.5, 50, and 1000 centistoke kinematic viscosities, and mercury. The experiments covered a range of Rayleigh numbers between 1.51(10)5 and 6.76(10)8. and Prandtl numbers between 0.02 and 8750. Tests were made in cylindrical containers having copper tops and bottoms and insulating walls. For water and silicone oils the container was 5 in. in diam and 2 in. high. For mercury, two containers were used, both 5.28 in. in diameter, but one 1.39 in. high and another 2.62 in. high. In all cases the bottom plates were heated by electric heaters. The top plates were air-cooled for the water and silicone-oil experiments and water-cooled for the mercury tests. To prevent amalgamation, the copper plates of the mercury container were chromium plated. Surface temperatures were measured by thermocouples embedded in the plates. The test results indicate that the heat-transfer coefficients for all liquids investigated may be determined from the relationship Nu=0.069Ra13Pr0.074 In this equation the Nusselt and Rayleigh numbers are based on the distance between the copper plates. The results of this experiment are in reasonable agreement with the data reported by others who used larger containers and different fluids.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Bulk Liquid ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

Experimental Investigation of Natural Convection Heat Transfer in Volumetrically Heated Spherical Segments

1996 ◽  
Vol 118 (1) ◽  
pp. 31-37 ◽  
Author(s):  
F. J. Asfia ◽  
B. Frantz ◽  
V. K. Dhir
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Reactor Vessel ◽  
Core Material ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
External Cooling

External cooling of a light water reactor vessel by flooding of the concrete cavity with subcooled water is one of several management strategies currently being considered for accidents in which significant relocation of core material is predicted to occur. At present, uncertainty exists with respect to natural convection heat transfer coefficients between the pool of molten core material and the reactor vessel wall. In the present work, experiments were conducted to examine natural convection heat transfer in internally heated partially filled spherical pools with external cooling. In the experiments, Freon-113 was contained in a Pyrex bell jar, which was cooled externally with subcooled water. The pool was heated using a 750 W magnetron taken from a conventional microwave. The pool had a nearly adiabatic free surface. The vessel wall temperature was not uniform and varied from the stagnation point to the free surface. A series of chromel–alumel thermocouples was used to measure temperatures in both steady-state and transient conditions. Each thermocouple was placed in a specific vertical and radial location in order to determine the temperature distribution throughout the pool and along the inner and outer walls of the vessel. In the experiments, pool depth and radius were varied parametrically. Both local and averages heat transfer coefficients based on pool maximum temperature were obtained. Rayleigh numbers based on pool height were varied from 2 × 1010 to 1.1 × 1014. Correlations for the local heat transfer coefficient dependence on pool angle and for the dependence of average Nusselt number on Rayleigh number and pool depth have been developed.

Thermal Effects During Infrared Solder Reflow—Part I: Heat Transfer Mechanisms

1992 ◽  
Vol 114 (1) ◽  
pp. 41-47 ◽  
Author(s):  
N. J. Fernandes ◽  
T. L. Bergman ◽  
G. Y. Masada
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Convective Heating ◽  
Transfer Coefficients ◽  
Thermally Induced ◽  
Heat Transfer Coefficients ◽  
Model Predictions ◽  
Transient Thermal ◽  
Transfer Mechanisms ◽  
Simple Numerical Model

An experimental study has been conducted to reveal the relevant heat transfer mechanisms which exist within an infrared reflow oven. Simulated card assemblies are used and their transient thermal responses, induced by combined radiative and convective heating, are measured. A simple numerical model is developed with which relevant heat transfer mechanisms are identified and quantified. The study shows that radiative and mixed convective heat transfer processes induce a variety of system thermal responses. Model predictions, which incorporate measured forced convection heat transfer coefficients and accurate descriptions of surface-to-surface radiative exchange, are in excellent agreement with experimental data for cases where the thermally induced buoyancy forces within the oven air are relatively small. The results of the experimental and analytical study provide guidelines for the development of more sophisticated models of the infrared reflow process.

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