An Overview of Surface Roughness Effects on Nucleate Boiling Heat Transfer!2009-10-31!2010-01-01!2010-04-16! (original) (raw)
Related papers
Experimental Thermal and Fluid Science, 2009
This paper presents results of an experimental investigation carried out to determine the effects of the surface roughness of different materials on nucleate boiling heat transfer of refrigerants R-134a and R-123. Experiments have been performed over cylindrical surfaces of copper, brass and stainless steel. Surfaces have been treated by different methods in order to obtain an average roughness, Ra, varying from 0.03 lm to 10.5 lm. Boiling curves at different reduced pressures have been raised as part of the investigation. The obtained results have shown significant effects of the surface material, with brass being the best performing and stainless steel the worst. Polished surfaces seem to present slightly better performance than the sand paper roughened. Boiling on very rough surfaces presents a peculiar behavior characterized by good thermal performance at low heat fluxes, the performance deteriorating at high heat fluxes with respect to smoother surfaces.
International Journal of Engineering Sciences and Research Technology, 2016
The effect of surface roughness on nucleate boiling heat transfer is analytically explored over a wide range of roughness values in water and Flourinent FC-77,two fluids with different thermal poperties and wetting characteristics.The test surfaces ranged from a polished surface of 0.045μm to 10.5μm.Different trends were observed in the heat transfer coefficient ,percentage of vapour and Vapour generated time with respect to surface roughness between the two fluids on the same set of surfaces.For FC-77,the percentage of vapour developed was increased continually with increasing roughness.For water,on the other hand,surfaces of intermediate roughness and maximum roughnessdisplayed similar values of percentage of vapour.While the roughest surface showed maximum percentage of vapour.The heat transfer coefficients and percentage of vapour developed were more strongly influenced by Fc-77than with water.At a very least vapour generated time of 0.4sec Fc-77 developed maximum percentage of vapour than with water.
Concerning the Effect of Surface Material on Nucleate Boiling Heat Transfer of R-113
ASME/JSME 2011 8th Thermal Engineering Joint Conference, 2011
This paper presents results of an experimental investigation carried out to determine the effects of surface material on nucleate pool boiling heat transfer of refrigerant R113. Experiments were performed on horizontal circular plates of brass, copper and aluminum. The heat transfer coefficient was evaluated by measuring wall superheat and effective heat flux removed by boiling. The experiments were carried out in the heat flux range of 8 to 200 kW/m 2. The obtained results have shown significant effect of surface material, with copper providing the highest heat transfer coefficient among the samples, and aluminum the least. There was negligible difference at low heat fluxes, but copper showed 23% better performance at high heat fluxes than aluminum and 18% better than brass.
Nucleate Pool Boiling Heat Transfer of Refrigerants Using Coated Surfaces
2019
This work presents the experimental study of nucleated pool boiling heat transfer of R-134a and R-410A on a horizontal coated heating surface. The heating surface dimensions are 25.4 mm outer diameter and 116 mm effective length. The coated surfaces were fabricated by flame spraying technique. The copper powder was used as a coating material applied to the outer surface of copper tube. The experiments were performed for heat flux range of 5–50 kWm−2 at saturation temperature of 10°C. The heat transfer coefficients of both refrigerants demonstrated the same trends with applied heat flux increase and their magnitudes increases with increasing the value of applied heat flux. The present study also includes the effects of heat flux and coating parameter on boiling characteristics. The boiling heat transfer coefficient is enhanced by 1.9 times that of plain surface. An empirical correlation was also developed to predict the heat transfer coefficient with a mean error of 13%.
Experimental study of nucleate boiling of halocarbon refrigerants on cylindrical surfaces
International Journal of Heat and Mass Transfer, 2003
The present paper reports the results of an experimental investigation of saturated pool boiling of halocarbon refrigerants on cylindrical surfaces of different materials. Experiments covered a wide range of reduced pressures and heat fluxes, being carried out on copper, brass and stainless steel surfaces with different finishing conditions. The obtained results are discussed with regard to the controlled physical and operational parameters of the investigation. An empirical correlation is proposed in terms of reduced pressures. The performance of the correlation can be deemed adequate, considering that it compares well with experimental results of different authors.
Surface roughness variation effects on copper tubes in pool boiling of water
International Journal of Heat and Mass Transfer, 2020
Results showing the effects of varying the surface roughness on copper tubes in pool boiling of water are presented in this study. To obtain different surface roughness values of each sample, the copper tubes were rotated with an electric rotor and sanded using sandpaper of different grit sizes. The average surface roughness values of the plain copper tubes were in the range 0.032-0.544 μm. All experimental samples were horizontally oriented, and experiments were carried out in ambient conditions up to a moderate heat flux regime (450 kW/m 2). Moreover, for a comparative analysis, a sample with a rough surface and hydrophobic patterns was included in this study. Compared with the smoothest surface, the aforementioned rough sample exhibited a heat transfer coefficient that was up to a factor 1.5 higher for the highest evaluated heat flux. These findings show that even small increments in the surface roughness along with the addition of hydrophobic patterns can significantly lower the wall superheat temperature and increase the heat transfer coefficient of copper tubes. Furthermore, supported by high-speed imaging of the experiment, it was observed that increasing the surface roughness caused bubbles to depart when their diameter was larger, and the nucleation site density and bubble departure frequency increased. In contrast, the rough surface with hydrophobic patterns exhibited the best overall enhancement, including the characteristics mentioned above of the rough surfaces along with a uniform distribution of the bubbles around the surface.
Influence of surface topography in the boiling mechanisms
The present paper addresses the qualitative and quantitative analysis of the pool boiling heat transfer over micro-structured surfaces. The surfaces are made from silicon chips, in the context of pool boiling heat transfer enhancement of immersion liquid cooling schemes for electronic components. The first part of the analysis deals with the effect of the liquid properties. Then the effect of surface micro-structuring is discussed, covering different configurations, from cavities to pillars being the latter used to infer on the potential profit of a fin-like configuration. The use of rough surfaces to enhance pool boiling mainly stands on the arguments that the surface roughness will increase the liquid–solid contact area, thus enhancing the convection heat transfer coefficient and will promote the generation of nucleation sites. However, one should not disregard bubble dynamics. Indeed, the results show a strong effect of bubble dynamics and particularly of the interaction mechanisms in the overall cooling performance of the pair liquid–surface. The inaccurate control of these mechanisms leads to the formation of large bubbles and strong vertical and horizontal coalescence effects promote the very fast formation of a vapor blanket, which causes a steep decrease of the heat transfer coefficient. This effect can be strong enough to prevail over the benefit of increasing the contact area by roughening the surface. For the micro-patterns used in the present work, the results evidence that one can reasonably determine guiding pattern characteristics to evaluate the intensity of the interaction mechanisms and take out the most of the patterning to enhance pool boiling heat transfer, when using micro-cavities. Instead, it is far more difficult to control the appearance of active nucleation sites and the optimization of the patterns allowing a reasonable control of the interaction mechanisms and in particular of horizontal coalescence, when dealing with the patterns based on micro-pillars. Hence, providing an increase of the liquid contact area by an effective increase of the roughness ratio is not enough to assure a good performance of the micro-structured surface. Despite it was not possible to clearly evidence a pin–fin effect or of an additional cooling effect due to liquid circulation between the pillars, the results show a significant increase of the heat transfer coefficient of about 10 times for water and 8 times for the dielectric fluid, in comparison to the smooth surface , when the micro-patterning based on pillars is used.
International Journal of Automotive Engineering, 2021
To improve internal combustion engine cooling systems, it is required to utilize the nucleate boiling heat transfer. Previous studies revealed it is affected by surface roughness, flow velocity, and degree of subcooling. This study investigated the heat transfer mechanisms (latent heat transport mechanism, sensible heat transport mechanism, and bubble agitation mechanism) when changing the above parameters. It was found that the increase in flow velocity and degree of subcooling increased the heat transfer due to the latent and sensible heat transport, while the increase in surface roughness increased the heat transfer due to the sensible heat transport and bubble agitation.
Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review
Energies
Nucleate boiling is a phase change heat transfer process with a wide range of applications i.e., steam power plants, thermal desalination, heat pipes, domestic heating and cooling, refrigeration and air-conditioning, electronic cooling, cooling of turbo-machinery, waste heat recovery and much more. Due to its quite broad range of applications, any improvement in this area leads to significant economic, environmental and energy efficiency outcomes. This paper presents a comprehensive review and critical analysis on the recent developments in the area of micro-nano scale coating technologies, materials, and their applications for modification of surface geometry and chemistry, which play an important role in the enhancement of nucleate boiling heat transfer. In many industrial applications boiling is a surface phenomenon, which depends upon its variables such as surface area, thermal conductivity, wettability, porosity, and roughness. Compared to subtractive methods, the surface coati...