The Use of Thin Films for Increasing Evaporation and Condensation Rates in Process Equipment

1959 ◽  
Vol 81 (4) ◽  
pp. 297-306 ◽  
Author(s):  
E. L. Lustenader ◽  
R. Richter ◽  
F. J. Neugebauer
Keyword(s):  
Heat Transfer ◽  
Thin Films ◽  
Surface Tension ◽  
Experimental Investigation ◽  
Process Equipment ◽  
Test Apparatus ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation

This paper describes an experimental investigation of an evaporating and condensing test apparatus in which over-all heat-transfer coefficients as high as 8000 Btu/(hr) (sq ft) (deg F) were obtained with water by utilizing thin films both in evaporation and condensation. The films were obtained by wiping on the evaporating surface and utilizing surface tension effects on the condensing surface. The phenomena on both the evaporating and the condensing surfaces are amenable to theory.

Evaporation and Condensation Heat Transfer and Pressure Drop in Horizontal, 12.7-mm Microfin Tubes With Refrigerant 22

1990 ◽  
Vol 112 (4) ◽  
pp. 1041-1047 ◽  
Author(s):  
L. M. Schlager ◽  
M. B. Pate ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Smooth Tube ◽  
Working Fluid ◽  
Test Apparatus ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Microfin Tubes ◽  
The Heat Transfer Coefficient

Using R-22 as the working fluid, a series of tests was performed to determine the evaporation and condensation performance of three 12.7-mm o.d. tubes having many small, spiral inner fins. The tubes, referred to as microfin tubes, had a 11.7-mm maximum i.d., 60 or 70 fins with heights ranging from 0.15 to 0.30 mm, and spiral angles from 15 to 25 deg. A smooth tube was also tested to establish a basis of comparison. The test apparatus had a straight, horizontal test section with a length of 3.67 m and was heated or cooled by water circulated in a surrounding annulus. Nominal evaporation conditions were 0 to 5°C (0.5 to 0.6 MPa) with inlet and outlet qualities of 15 and 85 percent, respectively; condensation conditions were 39 to 42°C (1.5 to 1.6 MPa) with inlet and outlet qualities of 85 and 10 percent, respectively. Mass flux varied from 75 to 400 kg/m2·s. The average heat transfer coefficients in the microfin tubes, based on a nominal equivalent smooth tube area, were 1.6 to 2.2 times larger for evaporation and 1.5 to 2.0 times larger for condensation than those in the smooth tube. The pressure drop increased, but by a smaller factor than the heat transfer coefficient.

scholarly journals Experimental Study on the Evaporation and Condensation Heat Transfer Characteristics of a Vapor Chamber

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 11
Author(s):  
Yanfei Liu ◽  
Xiaotian Han ◽  
Chaoqun Shen ◽  
Feng Yao ◽  
Mengchen Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Condensation Heat Transfer ◽  
Transfer Performance ◽  
Vapor Chamber ◽  
Filling Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation

A vapor chamber can meet the cooling requirements of high heat flux electronic equipment. In this paper, based on a proposed vapor chamber with a side window, a vapor chamber experimental system was designed to visually study its evaporation and condensation heat transfer performance. Using infrared thermal imaging technology, the temperature distribution and the vapor–liquid two-phase interface evolution inside the cavity were experimentally observed. Furthermore, the evaporation and condensation heat transfer coefficients were obtained according to the measured temperature of the liquid near the evaporator surface and the vapor near the condenser surface. The effects of heat load and filling rate on the thermal resistance and the evaporation and condensation heat transfer coefficients are analyzed and discussed. The results indicate that the liquid filling rate that maximized the evaporation heat transfer coefficient was different from the liquid filling rate that maximized the condensation heat transfer coefficient. The vapor chamber showed good heat transfer performance with a liquid filling rate of 33%. According to the infrared thermal images, it was observed that the evaporation/boiling heat transfer could be strengthened by the interference of easily broken bubbles and boiling liquid. When the heat input increased, the uniformity of temperature distribution was improved due to the intensified heat transfer on the evaporator surface.

Local Two-Phase Flow Heat Transfer in Plate Heat Exchangers

2007 ◽  
Author(s):  
Stephan Kabelac ◽  
Sebastian W. Freund
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Local Heat ◽  
Theoretical Development ◽  
Condensation Process ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Flow Heat

Experimental results on quasi-local heat transfer coefficients for evaporation and condensation in PHEs related to vapor quality, mass flow rate and heat flux are presented in this paper. The data is obtained from a refrigeration cycle involving a PHE evaporator and a PHE condenser with a secondary fluid loop. The considered refrigerants are ammonia and R-134a. Evaporator and condenser are equipped with multiple thermocouples along the plates, which allow for the deduction of local heat flux and heat transfer coefficients on seven subsections of the plates. The data resolves for the first time the complete evaporation and condensation process along a plate channel and thus may contribute to the understanding of flow distribution and heat transfer mechanisms. The results show an increase of heat transfer coefficients with the vapor quality and the effects of mass flux and heat flux. The results conclude that parallel flow arrangement is advantageous for evaporation while counter flow enhances condensation heat transfer. Plates with low pitch angle chevron corrugations increase the evaporation. Comparisons with the limited available data from literature and various correlations indicate the need for further theoretical development. The data may be suitable for developing correlations of the thermo-hydraulic performance of plate evaporators and condensers as a function of flow, heat flux and plate parameters, which are not established in literature.

scholarly journals Experimental determination of the heat transfer coefficient during evaporation and boiling of thin liquid film

2018 ◽  
Vol 194 ◽  
pp. 01022
Author(s):  
Anastasia Islamova
Keyword(s):  
Heat Transfer ◽  
Thin Films ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thin Liquid Film ◽  
Distilled Water ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient

Thin films evaporation of distilled water, ethanol and HFE-7100 liquid was experimentally studied. The dependences of heat transfer coefficients in time were determined. It has been established that with a decrease in the layer thickness of distilled water and ethanol, the heat transfer coefficient increases. For the HFE liquid, the nature of the change is different: as the time increases, the heat transfer coefficient decreases.

Liquid-Vapor Oscillating Flow and Heat Transfer in a U-Shaped Minichannel With Internal Wick Structure

2009 ◽  
Author(s):  
Jiajun Xu ◽  
Yuwen Zhang ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Transfer Coefficients ◽  
Oscillating Heat Pipe ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Flow And Heat Transfer ◽  
Wick Structure ◽  
Liquid Vapor

Liquid-vapor oscillating flow and heat transfer in a vertically placed oscillating heat pipe (OHP) with a sintered particle wick structure inside are analyzed in this paper. The evaporation and condensation heat transfer coefficients are obtained by solving the microfilm evaporation and condensation on the sintered particles. The sensible heat transfer between the liquid slug and the channel wall are obtained by analytical solution or empirical correlations, depending on whether the liquid flow is laminar or turbulent. The effects of the maximum evaporation and condensation angles on the oscillatory flow, as well as sensible and latent heat transfer are analyzed.

scholarly journals An Experimental Investigation of Heat Transfer Coefficients in a Spanwise Rotating Channel With Two Opposite Rib-Roughened Walls

1989 ◽  
Author(s):  
M. E. Taslim ◽  
A. Rahman ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Reynolds Numbers ◽  
Blockage Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Rotating Channel

Liquid crystals are used in this experimental investigation to measure the heat transfer coefficient in a spanwise rotating channel with two opposite rib-roughened walls. The ribs (also called turbulence promoters or turbulators) are configured in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90° for all cases. Results are presented for three values of turbulator blockage ratio, e/Dh (0.1333, 0.25, 0.333) and for a range of Reynolds numbers from 15,000 to 50,000 while the test section is rotated at different speeds to give Rotational Reynolds numbers between 450 and 1800. The Rossby number range is 10 to 100 (Rotation number of 0.1 to 0.01). The effect of turbulator blockage ratios on heat transfer enhancement is also investigated. Comparisons are made between the results of geometrically identical stationary and rotating passages of otherwise similar operating conditions. The results indicate that a significant enhancement in heat transfer is achieved in both the stationary and rotating cases, when the surfaces are roughened with turbulators. For the rotating case, a maximum increase over that of the stationary case of about 45% in the heat transfer coefficient is seen for a blockage ratio of 0.133 on the trailing surface in the direction of rotation and the minimum is a decrease of about 6% for a blockage ratio of 0.333 on the leading surface, for the range of rotation numbers tested. The technique of using liquid crystals to determine heat transfer coefficients in this investigation proved to be an effective and accurate method especially for nonstationary test sections.

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