Influence of Selected Parameters on Boiling Heat Transfer in Minichannels

2004 ◽  
Author(s):  
Magdalena Piasecka ◽  
Mieczyslaw E. Poniewski
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Rectangular Section ◽  
Liquid Crystal Thermography ◽  
Boiling Incipience

The experimental investigations cover heat transfer of refrigerants R 123 and R 11 flowing through vertical minichannels of 40 mm wide rectangular section and depths of 1 mm, 1.5 mm and 2 mm. The heating foil, supplied with controlled direct current, constitutes one of the surfaces of the minichannel. The liquid crystal thermography technique is applied in order to measure the two-dimensional temperature field of the heating surface. The investigations focus on the transition from single-phase forced convection to nucleate boiling, i.e. in the zone of boiling incipience. The present work aims to examine and analyze how the selected parameters (inlet pressure, inlet liquid subcooling, liquid flow velocity) affect nucleate boiling incipience for various geometry (changeable depth) of the minichannel. Furthermore, the investigations are intended to develop a correlation for the calculations of the Nusselt number under the conditions of boiling incipience in the minichannel. The equations are derived as modifications of the already developed ones [Piasecka, 2002; Piasecka and Poniewski, 2003b,c; Piasecka et al., 2004] and as a function of changeable parameters in the experimental investigations.

An Experimental Study of Transition and Film Boiling Heat Transfer in Liquid-Saturated Porous Bed

1986 ◽  
Vol 108 (1) ◽  
pp. 117-124 ◽  
Author(s):  
S. Fukusako ◽  
T. Komoriya ◽  
N. Seki
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Circular Cylinder ◽  
Boiling Heat Transfer ◽  
Heating Surface ◽  
Local Maximum ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Experimental Investigations ◽  
Porous Bed

Experimental investigations of transition and film boiling in a liquid-saturated porous bed are reported. The porous bed contained in a vertical circular cylinder is made up of packed spherical beads whose diameters range from 1.0 to 16.5 mm, while the depth of the bed overlying the heating surface varies from 10 to 300 mm. Water and fluorocarbon refrigerants R-11 and R-113 are adopted as testing liquids. Special attention is focused on the effect of the diameter of spherical beads on boiling heat transfer in the transition boiling region. It is found that for the small bead diameters the steady boiling heat transfer rises monotonically with temperature from nucleate boiling through the film boiling region, without going through a local maximum.

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.

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.

A General Correlation for Saturated Two-Phase Flow Boiling Heat Transfer Inside Horizontal and Vertical Tubes

1990 ◽  
Vol 112 (1) ◽  
pp. 219-228 ◽  
Author(s):  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Experimental Investigations ◽  
Mean Deviation ◽  
Transfer Coefficients ◽  
Flow Boiling Heat Transfer ◽  
Dependent Parameter ◽  
Vertical Tubes

A simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes. It was based on a model utilizing the contributions due to nucleate boiling and convective mechanisms. It incorporated a fluid-dependent parameter Ffl in the nucleate boiling term. The predictive ability of the correlation for different refrigerants was confirmed by comparing it with the recent data on R-113 by Jensen and Bensler (1986) and Khanpara et al. (1986). In the present work, the earlier correlation is further refined by expanding the data base to 5246 data points from 24 experimental investigations with ten fluids. The proposed correlation, equations (4) and (5), along with the constants given in Tables 3 and 4, gives a mean deviation of 15.9 percent with water data, and 18.8 percent with all refrigerant data, and it also predicts the correct hTP versus x trend as verified with water and R-113 data. Additional testing with recent R-22 and R-113 data yielded the lowest mean deviations among correlations tested. The proposed correlation can be extended to other fluids by evaluating the fluid-dependent parameter Ffl for that fluid from its flow boiling or pool boiling data.

Some Possible Critical Conditions in Nucleate Boiling

1963 ◽  
Vol 85 (2) ◽  
pp. 89-99 ◽  
Author(s):  
Yan-Po Chang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Maximum Rate ◽  
Unit Area ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Critical Conditions ◽  
Bubble Generation ◽  
Basic Ideas

The primary purpose of this paper is to introduce into boiling heat transfer certain basic ideas from which several critical conditions are derived. The heat transfer in nucleate boiling is considered as being limited by the maximum rate of bubble generation from a unit area of the heating surface. With certain simplified assumptions, an equation is obtained for the first critical heat flux of nucleate boiling with and without forced convection and subcooling.

Generalized Correlation of Boiling Heat Transfer

1959 ◽  
Vol 81 (1) ◽  
pp. 37-42 ◽  
Author(s):  
S. Levy
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heated Surface ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Generalized Equation ◽  
Test Results ◽  
Nucleate Boiling Heat Transfer ◽  
Generalized Correlation ◽  
Good Agreement

A generalized equation to describe surface boiling of liquids is derived. The expression which correlates all fluid independently of pressure and heating surface-fluid combination is QA=kLCLρL2σTsρL-ρV1BLΔT3 The form of the relation was obtained from a simplified model of heat transfer to the bubbles close to the heated surface. The coefficient BL, determined empirically, was found to be a function only of the product ρVhfg and is shown in Fig. 4. Good agreement between test results and the derived equation was obtained for pool boiling and nucleate boiling heat transfer of subcooled and vapor-containing liquids.

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