An Experimental Investigation of the Effect of Surface Conditions on Nucleate Pool Boiling Heat Transfer to Liquid Nitrogen from a Horizontal Surface PDF Download
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Author: Michael Damon Maynard
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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A system was designed to investigate experimentally the mechanism of nucleate pool boiling heat transfer using commercial grade liquid nitrogen as a working fluid. A circular horizontal flat plate five square centimeters in area was utilized as a boiler surface. The effect of various surface parameters on the characteristic heat flux versus (Tw-Ts) curve at atmospheric conditions was determined. Surfaces used included a highly polished mirror surface, a mirror surface coated with oxide, a mirror surface coated with grease, a roughened surface, and a roughened surface coated with Teflon, all fabricated from commercial electrical tough pitch copper. The final surface used was a Nickel 200 highly polished mirror surface. The data from the copper surface with a mirror finish was in agreement with the data of previous investigations. The effects of roughness, contaminants, hysteresis, and boiler surface material were discussed. A comparison was made on incipient boiling heat fluxes. The results indicate that the surface conditions play a major role in nucleate pool boiling heat transfer to liquid nitrogen.
Author: Michael Damon Maynard
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Book Description
A system was designed to investigate experimentally the mechanism of nucleate pool boiling heat transfer using commercial grade liquid nitrogen as a working fluid. A circular horizontal flat plate five square centimeters in area was utilized as a boiler surface. The effect of various surface parameters on the characteristic heat flux versus (Tw-Ts) curve at atmospheric conditions was determined. Surfaces used included a highly polished mirror surface, a mirror surface coated with oxide, a mirror surface coated with grease, a roughened surface, and a roughened surface coated with Teflon, all fabricated from commercial electrical tough pitch copper. The final surface used was a Nickel 200 highly polished mirror surface. The data from the copper surface with a mirror finish was in agreement with the data of previous investigations. The effects of roughness, contaminants, hysteresis, and boiler surface material were discussed. A comparison was made on incipient boiling heat fluxes. The results indicate that the surface conditions play a major role in nucleate pool boiling heat transfer to liquid nitrogen.
Author: Michael Damon Maynard
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 0
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Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: Harold Wayne George
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Category :
Languages : en
Pages :
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Author: Naval Postgraduate School (U.S.)
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ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 628
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Author:
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ISBN:
Category : Science
Languages : en
Pages : 760
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Author: Abbas M. Sinnarwalla
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ISBN:
Category : Heat
Languages : en
Pages : 100
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"The purpose of this investigation was to determine the effect of surface conditions on the heat transfer for nucleate pool boiling from flat horizontal surfaces. Experiments were carried out using Refrigerant-1l at atmospheric pressure as the test fluid with Inconel-600 as the heater material. The heat transfer coefficient was determined for mirror finished, chemically etched, glass beaded and sandpaper roughened heater surfaces over heat flux ranging for 0 to 18000 BTU/HR SQ FT. At a given heat flux, the heat transfer coefficient was found to be the lowest for mirror finished surface and the highest for sandpaper roughened surface"--Abstract, leaf ii.
Author:
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Category :
Languages : en
Pages :
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Author: Shikha Ebrahim
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ISBN:
Category :
Languages : en
Pages :
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In this research, minimum film boiling temperature (Tmin) is quantitatively determined as a function of the initial substrate temperature, liquid subcooling, surface thermophysical properties and surface conditions. Since Tmin defines the boundary between the film and transition boiling regimes, its value is significant for the design of an emergency core cooling system following a hypothetical loss-of-coolant accident (LOCA) in a nuclear power plant. When a sufficiently heated surface is plunged in a water pool, a vapor blanket is generated around the test section acting as a heat transfer insulator due to the poor thermal conductivity of the vapor. At temperatures lower than Tmin, the heat transfer is dramatically enhanced owing the collapse of the vapor film allowing direct physical contact between the water and the heated surface. Therefore, it is very important to explore methods and techniques that increase this temperature in order to improve the safety of nuclear reactors. A test facility was designed and constructed to conduct quenching experiments using vertical rods. Seven cylindrical test samples were fabricated with embedded thermocouples inside the cladding material. The thermocouples were connected to a data acquisition system in order to measure the temperature history during the experiments. The temperature and heat flux at the surface were calculated using an inverse heat conduction code along with an advance image processing technique to quantitatively characterize the liquid-vapor interfacial waves, vapor layer thickness, Tmin, quenching temperature, quenching time, and quench front velocity in the film boiling heat transfer regime. Visualization of the boiling behavior was captured by a high-speed camera at a frame rate of 750 frames per second (fps). The thermocouple data and the captured videos were synchronized to couple the behavior of the vapor layer with the thermal behavior of the heated sample. Various characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) associated with Energy-dispersive X-ray spectroscopy (EDS), and field emission scanning electron were employed to identify the phases, chemical composition, and surface microstructure of the Inconel-600 before and after being used in a 7 x 7 rod bundle facility. Micro- and nanoparticles composed of nickel, chromium, and iron oxides were observed at the surface of the oxidized Inconel samples. It was found that the porous microstructure coupled with the increase in liquid spreading played a significant role in the enhancement of the film boiling heat transfer. Finally, the heat transfer behavior in the film boiling regime was investigated by calculating the heat transfer coefficient and Nusselt number for various cases. The novelty of this research is the coupling between the results of the quenching experiments and the surface characterization analyses that prompted the development of a new correlation for Tmin. This correlation adequately captures the effects of liquid subcooling, porosity of the oxide layer, and system pressure.
Author: P. J. Marto
Publisher:
ISBN:
Category : Boiling water reactors
Languages : en
Pages : 127
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