scholarly journals A LITERATURE SURVEY ON THE APPLICABILITY OF STEADY-STATE HEAT-TRANSFER COEFFICIENTS TO TRANSIENTS IN POWER OR IN FLOW WITH SINGLE-PHASE FLOW AND WITH TWO-PHASE FLOW

1957 ◽  
Author(s):  
R H Norris
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Literature Survey ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Steady State Heat ◽  
Steady State Heat Transfer

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.

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.

Single Phase and Two Phase Flow Characteristics and Heat Transfer in Micro-Fin Tubes

2015 ◽  
Author(s):  
Jun-ye Li ◽  
Si-pu Guo ◽  
Jing Zhang ◽  
Wei Li ◽  
Jin-jia Wei ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients ◽  
Error Band ◽  
Heat Transfer Coefficients ◽  
New Correlation ◽  
Fin Tubes

An experimental investigation was performed with R22 and R410a for single-phase flow, evaporation and condensation inside five micro-fin tubes of various geometries to obtain pressure drop and heat transfer characteristics. The results suggest single-phase flow heat transfer coefficients are increased by 46% to 64% compared with smooth tubes values. Tube geometries that had higher evaporation heat transfer coefficients or higher condensation heat transfer coefficients were identified. Condensation pressure drop characteristics also varied with tube geometry. Based on experiment data, a new correlation which contains the characteristics of a liquid film in annular flow is established. The new correlation can predict the experimental data within an error band of 15% and, for 77% of the data from the literature, within an error band of 30%. The Choi et al. correlation can predict the present condensation pressure drop data within a 20% error band and the Yu and Koyama correlation can predict the present condensation heat transfer coefficient data within 25%.

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.

An Experimental Investigation of Gas-Liquid Heat Transfer in Rectangular Micro-Channels

2013 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises ◽  
Piyawat Kuaseng ◽  
Chompunut Nuibutr ◽  
Wattana Chanphan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Camera System ◽  
Micro Channels ◽  
Flow Mechanisms

The investigations of heat transfer and fluid flow characteristics of non-boiling air-water flow in micro-channels are experimentally studied. The gas-liquid mixture from y-shape mixer is forced to flow in the 21 parallel rectangular microchannels with 40 mm long in the flow direction. Each channel has a width and a depth of 0.45 and 0.41 mm, respectively. Flow visualization is feasible by incorporating the stereozoom microscope into the camera system and different flow patterns are recorded. The experiments are performed under low superficial velocities. Two-phase heat transfer gives better results when compared with the single-phase flow. It is found from the experiment that heat transfer enhancement up to 53% is obtained over the single-phase flow. Also, the change in the configuration of the inlet plenum can result in the different two-phase flow mechanisms.

scholarly journals Two-dimensional heat transfer coefficients with simultaneous flow visualisations during two-phase flow boiling in a PDMS microchannel

2018 ◽  
Vol 130 ◽  
pp. 624-636 ◽  
Author(s):  
Sofia Korniliou ◽  
Coinneach Mackenzie-Dover ◽  
John R.E. Christy ◽  
Souad Harmand ◽  
Anthony J. Walton ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Pdms Microchannel

Heat Transfer Analysis of Microgrooved Evaporator and Condenser Surfaces Utilized in a High Heat Flux Two-Phase Flow Loop

2007 ◽  
Author(s):  
Edvin Cetegen ◽  
Thomas Baummer ◽  
Serguei Dessiatoun ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Heat ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Microgrooved Surface

This paper investigates the heat transfer and pressure drop analysis of micro grooved surfaces utilized in evaporators and condensers of a two-phase flow cooling loop. These devices utilize the vapor-liquid phase change to transfer large amounts of heat, and they offer substantially higher heat flux performance with lower pumping power than most liquid cooling technologies. Microgrooved surfaces, combined with force-fed evaporation and condensation technology discussed in this paper yield high heat transfer coefficients with low pressure drops. Our most recent results, aiming to test the limits of the technology, demonstrated dissipation of almost 1kW/cm2 from silicon electronics using HFE 7100 as the working fluid. In a compact two phase system, the heat generated by the electronic components can be absorbed by microgrooved evaporators and rejected through the microgrooved surface condensers to liquid cooled slots with high heat transfer coefficients and low pressure drops on the refrigerant side. In the case of air-cooling, the same microgrooved surface heat exchanger can reject heat with a heat transfer coefficient of 3847 W/cm2 and a pressure drop of 4156 Pa. These heat transfer processes have the added capability of being combined and used together in a self-contained system cooled either by liquid or air.

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