Nucleate Boiling Heat Transfer of Binary Mixtures at Low to Moderate Heat Fluxes

1999 ◽  
Vol 121 (2) ◽  
pp. 365-375 ◽  
Author(s):  
R. J. Benjamin ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Turbulent Natural Convection

A model for nucleate pool boiling heat transfer of binary mixtures has been proposed based on an additive mechanism. The contributing modes of heat transfer are (i) the heat transferred by microlayer evaporation, (ii) the heat transferred by transient conduction during the reformation of the thermal boundary layer, and (iii) the heat transferred by turbulent natural convection. The model takes into account the microroughness of the heating surface which has been defined quantitatively. The model compares satisfactorily with data obtained in the present study and in the literature. These data were obtained on a variety of heating surfaces such as a vertical platinum wire, a horizontal stainless steel tube and flat horizontal aluminium, and stainless steel surfaces (with various surface finishes) thereby demonstrating the validity of the model.

The Effects of Nucleate Boiling Versus Film Boiling on Heat Transfer in Power Boiler Tubes

1962 ◽  
Vol 84 (4) ◽  
pp. 365-371 ◽  
Author(s):  
H. S. Swenson ◽  
J. R. Carver ◽  
G. Szoeke
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Inside Surface ◽  
Film Boiling ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Steam Quality ◽  
Heat Transfer Coefficients

In large, subcritical pressure, once-through power boilers heat is transferred to steam and water mixtures ranging in steam quality from zero per cent at the bottom of the furnace to 100 per cent at the top. In order to provide design information for this type of boiler, heat-transfer coefficients for forced convection film boiling were determined for water at 3000 psia flowing upward in a vertical stainless-steel tube, AISI Type 304, having an inside diameter of 0.408 inches and a heated length of 6 feet. Heat fluxes ranged between 90,000 and 180,000 Btu/hr-sq ft and were obtained by electrical resistance heating of the tube. The operation of the experimental equipment was controlled so that nucleate boiling, transition boiling, and stable film boiling occurred simultaneously in different zones of the tube. The film boiling data were correlated with a modified form of the equation Nu = a a(Re)m(Pr)n using steam properties evaluated at inside surface temperature. Results of a second series of heat-transfer tests with tubes having a helical rib on the inside surface showed that nucleate boiling could be maintained to much higher steam qualities with that type of tube than with a smooth-bore tube.

Effects of Materials on the Heat Transfer Coefficient During Condensation and Evaporation of R410A

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Weiyu Tang ◽  
Tariq Amin Khan ◽  
Boren Zheng ◽  
Lei Wang ◽  
Wei Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Pool Boiling ◽  
Predictive Ability ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Roughness Effects ◽  
Aluminum Tube ◽  
Low Mass

Abstract An experimental investigation was conducted to demonstrate the effects of materials on the heat transfer characteristics of R410A during evaporation and condensation inside two horizontal plain tubes with the same inner diameter of 6 mm, but with two different materials of aluminum and stainless steel. The variation of vapor quality for the test section was kept in the range of 0.2–0.9, while mass velocities were allowed to vary from 100 to 400 kg/m2/s1. First, a series of single-phase and repetitive experiments were conducted to verify the accuracy and reliability of the test rig. Results of the evaporation experiments show that the plain aluminum tube performs best for all tested mass velocities. Several different correlations were employed to predict the present data, and their predictive ability was compared and discussed. Results indicate that the Liu and Winterton correlation could accurately predict the present results except for low mass velocities. Roughness effects were accounted for employing a correction factor. The larger roughness of the stainless steel tube was supposed to make the stainless steel tube perform better if roughness effects were accounted for, so the better performance of the aluminum tube was mainly attributed to the material effects. The pool boiling heat transfer as predicted by the VDI model was compared with the experimental results, and more obvious material effects have been found for pool boiling conditions. The minor differences between the two tubes in this case may be explained by the nucleate boiling suppression and incomplete wetting. For the condensation experiments, little difference was found between the two tested tubes, which means that the material and roughness effects may have had little influence on the thermal performance during condensation.

Ultrasonic augmentation in pool boiling heat transfer over external surfaces: A review

2020 ◽  
pp. 095440622095035
Author(s):  
Abhishek Swarnkar ◽  
Vikas J Lakhera
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat ◽  
Ultrasonic Field ◽  
Ultrasonic Waves ◽  
Heat Fluxes ◽  
Surface Topology

Boiling heat transfer is known for high heat fluxes at relatively small temperature differences. However, over the decades, technological innovations have demanded further augmentation in heat fluxes associated with boiling. Among the various active and passive methods, use of ultrasonic waves in boiling liquid has emerged as a proven technique for the required heat transfer improvement as demonstrated by a number of researchers. The present article reviews the application of ultrasonic waves in enhancing the heat transfer in various regimes of pool boiling. It has been found that the use of ultrasonic field is more promising in case of sub-cooled boiling as compared to saturated condition. Along with ultrasonic field of lower frequency and higher power, the usage of various passive techniques of surface improvement such as micro channel, surface topology, nano coatings etc. leads to further augmentation of heat transfer. Also, the relative placement of heating surface in ultrasonic wave field must be considered inevitably while designing an ultrasonic field assisted pool boiling system. It requires further investigations to conduct more parametric studies such as effect of pressure along with the usage of ultrasonic waves during sub- cooled boiling. Also during ultrasonic assisted pool boiling, various nano fluids can be tested for improving the heat transfer characteristics particularly in the saturated nucleate boiling regime.

Visualization of Boiling Heat Transfer on Micro Porous Coated Surface in Confined Space

2013 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chien-Fu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Two Phase ◽  
Nucleate Boiling Heat Transfer ◽  
Coated Surface

Numerous researches have been developed for pool boiling on microporous coated surface in the past decade. The nucleate boiling heat transfer was found to be increased by up to 4.5 times than that on uncoated surface. Recently, the two-phase micro heat exchangers have been considered for high flux electronic devices cooling. The enhancement techniques for improving the nucleate boiling heat transfer performance in the micro heat exchangers have gotten more importance. Previous studies of microporous coatings, however, have been restricted to boiling in unconfined space. No studies have been made on the feasibility of using microporous coatings for enhancing boiling in confined spaces. This study provides an experimental observation of the vapor generation and leaving processes on microporous coatings surface in a 1-mm confined space. It would be helpful for understanding the mechanism of boiling heat transfer and improving the design of two-phase micro heat exchangers. Aluminum particles of average diameter 20 μm were mixed with a binder and a carrier to develop a 150 μm thickness boiling enhancement paint on a 3.0 cm by 3.0 cm copper heating surface. The heating surface was covered by a thin glass plate with a 1 mm spacer to form a 1 mm vertical narrow space for the test section. The boiling phenomenon was recorded by a high speed camera. In addition to the three boiling regimes observed by Bonjour and Lallemand [1], i.e., isolated deformed bubbles, coalesced bubbles and partial dryout at low, moderate and high heat fluxes respectively in unconfined space, a suction and blowing process was observed at the highest heat flux condition. Owing to the space confinement, liquid was sucked and vapor was expelled periodically during the bubble generation process. This mechanism significantly enhanced the boiling heat transfer performance in confined space.

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