An Analysis of Film Condensation, Film Evaporation, and Single-Phase Heat Transfer for Liquid Prandtl Numbers From 10−3 to 104

1969 ◽  
Vol 91 (3) ◽  
pp. 413-420 ◽  
Author(s):  
H. R. Kunz ◽  
S. Yerazunis
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Film Condensation ◽  
Phase Flow ◽  
Interfacial Resistance ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Wide Range ◽  
Prandtl Numbers ◽  
Film Heat Transfer

Annular two-phase flow inside of circular tubes is analyzed for a wide range of film Reynolds and Prandtl numbers. This analysis is applied to the prediction of film heat transfer coefficients and film thicknesses for the cases of condensation and evaporation of pure substances inside tubes, two-component flow in tubes, and condensing falling films on vertical surfaces. The analysis is also extended to single-phase flow in tubes. Extensive comparisons are made with experimental and theoretical results of other investigators, indicating good agreement if consideration is given to liquid-vapor interfacial resistance to heat flow for cases involving phase transformation.

Experimental Study on Heat Transfer of Single-Phase Flow and Boiling Two-Phase Flow in Vertical Narrow Annuli

2002 ◽  
Author(s):  
Suizheng Qiu ◽  
Minoru Takahashi ◽  
Guanghui Su ◽  
Dounan Jia
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Two Phase Flow ◽  
Annular Channel ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Narrow Annuli ◽  
Narrow Gaps

Water single-phase and nucleate boiling heat transfer were experimentally investigated in vertical annuli with narrow gaps. The experimental data about water single-phase flow and boiling two-phase flow heat transfer in narrow annular channel were accumulated by two test sections with the narrow gaps of 1.0mm and 1.5mm. Empirical correlations to predict the heat transfer of the single-phase flow and boiling two-phase flow in the narrow annular channel were obtained, which were arranged in the forms of the Dittus-Boelter for heat transfer coefficients in a single-phase flow and the Jens-Lottes formula for a boiling two-phase flow in normal tubes, respectively. The mechanism of the difference between the normal channel and narrow annular channel were also explored. From experimental results, it was found that the turbulent heat transfer coefficients in narrow gaps are nearly the same to the normal channel in the experimental range, and the transition Reynolds number from a laminar flow to a turbulent flow in narrow annuli was much lower than that in normal channel, whereas the boiling heat transfer in narrow annular gap was greatly enhanced compared with the normal channel.

Simulation of Two-Phase Flow and Heat Transfer in Mini- and Micro-Channels for Concentrating Photovoltaics Cooling

2011 ◽  
Author(s):  
Devin Pellicone ◽  
Alfonso Ortega ◽  
Marcelo del Valle ◽  
Steven Schon
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Micro Scale ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Micro Channels

Advances in concentrating photovoltaics technology have generated a need for more effective thermal management techniques. Research in photovoltaics has shown that there is a more than 50% decrease in PV cell efficiency when operating temperatures approach 60°C. It is estimated that a waste heat load in excess of 500 W/cm2 will need to be dissipated at a solar concentration of 10,000 suns. Mini- and micro-scale heat exchangers provide the means for large heat transfer coefficients with single phase flow due to the inverse proportionality of Nusselt number with respect to the hydraulic diameter. For very high heat flux situations, single phase forced convection in micro-channels may not be sufficient and hence convective flow boiling in small scale heat exchangers has gained wider scrutiny due to the much higher achievable heat transfer coefficients due to latent heat of vaporization and convective boiling. The purpose of this investigation is to explore a practical and accurate modeling approach for simulating multiphase flow and heat transfer in mini- and micro-channel heat exchangers. The work is specifically aimed at providing a modeling tool to assist in the design of a mini/micro-scale stacked heat exchanger to operate in the boiling regime. The flow side energy and momentum equations have been implemented using a one-dimensional homogeneous approach, with local heat transfer coefficients and friction factors supplied by literature correlations. The channel flow solver has been implemented in MATLAB™ and embedded within the COMSOL™ FEM solver which is used to model the solid side conduction problem. The COMSOL environment allows for parameterization of design variables leading to a fully customizable model of a two-phase heat exchanger.

scholarly journals New Perspective for Heat Transfer Evaluation During Film Condensation Inside Tubes

2021 ◽  
Vol 39 (2) ◽  
pp. 390-402
Author(s):  
Yanán Camaraza-Medina
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Single Phase ◽  
Film Condensation ◽  
Mean Deviation ◽  
Two Phase ◽  
Wide Range ◽  
The Mean ◽  
Vertical Tubes

This paper presents the main results of the research developed by the author in his postdoctoral investigations on heat transfer calculations during film condensation inside tubes. The elements studied are combined in an analysis expression that provides a reasonable fit with the available experimental data, which includes a total of 22 fluids, including water, refrigerants and a wide range of organic substances, which condense inside horizontal, inclined and vertical tubes. These experimental data were obtained from the reports of 33 sources. Available data covers tube diameters from 2 to 50 mm, mass flow rates from 3 to 850 kg/(m2s), reduced pressures ranging from 0.0008 to 0.91, values for single-phase from 1 to , Reynolds number for two-phase from 900 to 594390, Reynolds number for single-phase from 65 to 84950 and vapor quality from 0.01 to 0.99. The mean deviation found for the analyzed data for horizontal tubes was 13.4%, while for the inclined and vertical tubes data the mean deviation was 14.9%. In all cases, the agreement of the proposed model is good enough to be considered satisfactory for practical design.

Simulation of Two-Phase Flow and Heat Transfer for Practical Design of Mini- and Micro-Channel Heat Exchangers

2011 ◽  
Author(s):  
Devin Pellicone ◽  
Alfonso Ortega ◽  
Marcelo del Valle ◽  
Steven Schon
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase ◽  
Hydraulic Diameter ◽  
Phase Flow ◽  
Micro Channel ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer

Mini- and micro-scale heat exchangers provide the means for large heat transfer coefficients with single phase flow due to the inverse proportionality of Nusselt number with respect to the hydraulic diameter. For very high heat flux situations, single phase forced convection in micro-channels may not be sufficient and hence convective flow boiling in small scale heat exchangers has gained wider scrutiny due to the much higher achievable heat transfer coefficients due to latent heat of vaporization and convective boiling. The purpose of this investigation is to explore a practical and accurate modeling approach for simulating multiphase flow and heat transfer in stacked mini- and micro-channel heat exchangers. The work is specifically aimed at providing the framework for the optimization of such devices. The model algorithm is described in detail and the effects of channel hydraulic diameter ranging from 150–300 μm and number of stacked layers on the thermal and hydrodynamic performance of the heat sinks are explored. The results from the two parameter study are used to suggest a design path for creating an optimal two-phase stacked microchannel heat exchanger.

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

Analytical Prediction of Heat Transfer in Tape Generated Swirl Flow

2017 ◽  
Author(s):  
R. J. Yadav ◽  
Sandeep Kore ◽  
V. N. Riabhole
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Swirl Flow ◽  
Twisted Tape ◽  
Analytical Prediction ◽  
Transfer Coefficients ◽  
Numerical Predictions ◽  
Twisted Tapes ◽  
Wide Range ◽  
Prandtl Numbers

Heat transfer and pressure drop characteristics in a circular tube with twisted tapes have been investigated experimentally and numerically using different working fluids by many researchers for wide range of Reynolds number. The swirl was generated by tape inserts of various twist ratios. The various twist ratios are considered Many researchers formed generalized correlations to predict friction factors and convective heat transfer coefficients with twisted tapes in a tube for a wide range of Reynolds numbers and Prandtl numbers. Satisfactory agreement was obtained between the present correlations and the data of others validate the proposed correlations. The experimental or numerical predictions were compared with earlier correlations revealing good agreement between them. From the literature review it is observed that most studies are mainly focused on the heat transfer enhancement using twisted tape by experimental or numerical solution. An investigation with analytical approach is rarely reported. Therefore, the main aim of the present work is to form a correlation from theoretical approach for Nusselt number for circular tube with twisted tape. Application of dimensional analysis to heat transfer in tape generated swirl flow is carried out.

Thermoreflectance Wall Temperature Measurement in Annular Two-Phase Flow

2019 ◽  
Author(s):  
Jason Chan ◽  
Brian E. Fehring ◽  
Roman W. Morse ◽  
Kristofer M. Dressler ◽  
Gregory F. Nellis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Annular Flow ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Dry Out

Abstract A thermoreflectance method to measure wall temperature in two-phase annular flow is described. In high heat flux conditions, momentary dry-out occurs as the liquid film vaporizes, resulting in dramatic decreases in heat transfer coefficient. Simultaneous liquid and vapor thermoreflectance measurements allow calculations of instantaneous and time-averaged heat transfer coefficients. Validation, calibration and uncertainty of the technique are discussed.

Heat Transfer in Annular Channel With Continuous Flow Twisting

2010 ◽  
Author(s):  
S. E. Tarasevich ◽  
A. B. Yakovlev
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Boiling ◽  
Annular Channel ◽  
Equivalent Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Diameter ◽  
Subcooled Flow Boiling ◽  
Annular Channels

In paper the experimental results on a heat transfer in annular channels with continuous twisting at length at one- and two-phase flows are observed. For a flow twisting the wire was spirally coiled on the central body of the annular channel (diameter of a wire is equal to annular gap altitude). Results of experimental data of a heat transfer of authors and various researchers at a single phase flow in annular channels with a continuous twisting are analyzed. Sampling of diagnostic variables (equivalent diameter and velocity) is spent and generalizing associations for heat transfer calculation on the concave and convex surfaces in a single-phase phase are offered. Also the technique of definition of temperature of the subcooled flow boiling beginning on surfaces of annular channels with a twisting is offered. Features of boiling, origination of heat transfer crisis and results of visualization of a two-phase flow structure in annular channels with twisting are described.

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