Experimental Study on Heat Transfer Characteristics of Water and Ethanol Flow Boiling in Micro-Channel

2013 ◽  
Vol 330 ◽  
pp. 788-791
Author(s):  
Xia Weng ◽  
Dong Yao Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Bond Number ◽  
Micro Channel ◽  
Vapor Quality ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

The Heat transfer characteristics of water and ethanol flow boiling in micro-channel are studied. Flow boiling of different mass and heat flux is carried out in 61 parallel microchannel with hydro diameter of 0.293mm, and the local heat transfer coefficient (HTC) of is calculated. The results indicate that the HTC decreases with the increasing of vapor quality, and depends on heat flux. Two latest correlations are used to predict the experiment, and the results indicate that the Bond number plays an important role in the correlation.

Experimental and Numerical Analyses of R134a Flow Boiling Heat Transfer Characteristics in an Evaporator Tube of Refrigeration System

2019 ◽  
Vol 27 (03) ◽  
pp. 1950024
Author(s):  
Zahraa Kareem Yasser ◽  
Ahmed J. Hamad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Refrigeration System ◽  
Heat Transfer Characteristics

The heat transfer characteristics of R134a flow boiling in a horizontal tube of an evaporator section for a refrigeration system of 310-W capacity are investigated experimentally and numerically. The experimental work was conducted using an evaporator tube test section of inner diameter 5.8[Formula: see text]mm and length 600[Formula: see text]mm. The ranges of investigated experimental data for heat flux, mass flux, saturation temperature and vapor quality were 13.8–36.6[Formula: see text]kW/m2, 52–105[Formula: see text]kg/m2[Formula: see text][Formula: see text][Formula: see text]s, [Formula: see text]–[Formula: see text]C and 0.2–1, respectively. Numerical analysis was based on two-phase flow turbulent model and this model was solved using the Ansys-18 code. The results showed that the effects of heat flux, mass velocity and saturation temperature on local heat transfer coefficient and pressure drop were greater compared to that of the refrigerant vapor quality. The enhancements in local heat transfer coefficient due to the increase in heat flux, mass and saturation temperature were 38%, 57% and 64%, respectively, within the prescribed test conditions. The influence of mass flux variation on pressure drop along the evaporator channel was higher in the range of 27% compared to the heat flux effect. The average deviations between experimental and numerical results of heat transfer coefficient and pressure gradient were 14% and 17%, respectively, while the same between the experimental and predicted results were 16% and 33%, respectively.

scholarly journals Flow boiling heat transfer characteristics of low GWP refrigerants in a vertical mini-channel

2020 ◽  
pp. 327-327
Author(s):  
Muhammad Asim ◽  
Zahid Anwar ◽  
Muhammad Farooq ◽  
Rabia Shaukat ◽  
Shahid Imran ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Operating Pressure ◽  
Vapor Quality ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow Boiling Heat Transfer ◽  
Wide Range

Flow boiling heat transfer characteristics in narrow channels have been investigated extensively by researchers due to its wide range of applications in micro-electromechanical systems (MEMS), however, being a complex transport process the controlling mechanisms still lack clarity in understanding. Refrigerants related environmental hazards also urged to look for alternative environment friendly refrigerants. It has been noticed that relatively less information is available in the literature specifically for environmentally benign mediums. This study is focused on experimental findings for flow boiling heat transfer performance of low GWP refrigerants (R152a, R600a, and R1234yf). The test object was a vertical stainless steel tube (1.60 mm inner diameter and heated surface length 245 mm), experiments were done under upward fluid flow conditions. The tested conditions were: heat flux 5-245 kWm-2, 50-500 kgm-2s-1 mass velocities while saturation temperatures were 27 and 32?C. The effects of operating parameters like heat and mass fluxes, saturation temperature, and vapor quality on heat transfer were analyzed in detail. It was noticed that heat transfer coefficients were significantly influenced by heat flux and operating pressure level whereas the same were not significantly affected by mass flux and vapor quality. The experimental data of heat transfer was compared with the prediction from various macro and micro scale correlations from the literature, reasonably good predictions were noticed with the correlation proposed by Mahmoud and Karayiannis [1].

Local Heat Transfer Characteristics in Simulated Electronic Modules

2003 ◽  
Vol 125 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Seong-Yeon Yoo ◽  
Jong-Hark Park ◽  
Min-Ho Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Dimensional Array ◽  
Transfer Characteristics

When heat is released by forced convection from electronic modules in a narrow printed circuit board channel, complex flow phenomena—such as stagnation and acceleration on the front surface, separation and reattachment on the top surface, wake or cavity flow near the rear surface—affect the heat transfer characteristics. The purpose of this study is to investigate how these flow conditions influence the local heat transfer from electronic modules. Experiments are performed on a three-dimensional array of hexahedral elements as well as on a two-dimensional array of rectangular elements. Naphthalene sublimation technique is employed to measure three-dimensional local mass transfer, and the mass transfer data are converted to their counterparts of the heat transfer process using the analogy equation between heat and mass transfer. Module location and streamwise module spacing are varied, and the effect of vortex generators on heat transfer enhancement is also examined. Dramatic change of local heat transfer coefficients is found on each surface of the module, and three-dimensional modules have a little higher heat transfer value than two-dimensional modules because of bypass flow. Longitudinal vortices formed by vortex generator enhance the mixing of fluids and thereby heat transfer, and the rectangular wing type vortex generator is found to be more effective than the delta wing type vortex generator.

Numerical Research on Heat Transfer Characteristics Analysis of Two Particles in Supercritical Water

2021 ◽  
Author(s):  
Xiaoyu Li ◽  
Zhenqun Wu ◽  
Huibo Wang ◽  
Hui Jin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Heat Transfer Characteristics ◽  
Particle Cluster ◽  
Two Phase ◽  
Transfer Characteristics

Abstract In the supercritical water (SCW)-particle two-phase flow of fluidized bed, the particles that make up the particle cluster interact with each other through fluid, and it will affect the flow and heat transfer. However, due to the complex properties of SCW, the research on particle cluster is lacking, especially in terms of heat transfer. This research takes two particles as an example to study the heat transfer characteristics between SCW and another particle when one particle exists. This research uses the distance and angle between the two particles as the influencing factors to study the average heat transfer rate and local heat transfer rate. In this research, it is found that the effect is obvious when L/D = 1.1. When L = 1.1D, the temperature field and the flow field will partially overlap. The overlap of the temperature field will weaken the heat transfer between SCW and the particle. The overlap of the flow field has an enhanced effect on the heat transfer between SCW and the particle. The heat transfer between SCW and particles is simultaneously affected by these two effects, especially local heat transfer rate. In addition, this research also found that as the SCW temperature decreases, the thermal conductivity and specific heat of SCW increases, which enhances the heat transfer between SCW and the particles. This research is of great significance for studying the heat transfer characteristics of SCW-particle two-phase flow in fluidized bed.

High heat flux flow boiling in silicon multi-microchannels – Part I: Heat transfer characteristics of refrigerant R236fa

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5400-5414 ◽  
Author(s):  
Bruno Agostini ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
Daniele Calmi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Heat Transfer Characteristics ◽  
Flux Flow ◽  
Transfer Characteristics

Heat Transfer Characteristics of a Radial Jet Reattachment Flame

1997 ◽  
Vol 119 (2) ◽  
pp. 258-264 ◽  
Author(s):  
J. W. Mohr ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Combustion Process ◽  
Local Heat ◽  
Operating Conditions ◽  
Recirculation Region ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.

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