Microscale Heat Transfer Measurements During Subcooled Pool Boiling of Pentane: Effect of Bubble Dynamics

2010 ◽  
Author(s):  
Payam Delgoshaei ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Growth Time ◽  
Two Phase ◽  
Time Resolved ◽  
Earth Gravity ◽  
Transfer Mechanisms

Measurements of space and time resolved heat transfer during subcooled pool boiling of pentane in earth gravity were obtained using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two high-speed cameras. The heat transfer mechanisms during bubble growth were found to be dependent on bubble dynamics and bubble growth time. Single phase heat transfer mechanisms (transient conduction and/or microconvection) were found to be dominant for single bubbles with short growth times. Two phase heat transfer mechanisms (microlayer evaporation and/or contact line evaporation) were found to be dominant for bubbles with longer growth times.

Microscale Heat Transfer Measurements of the Lateral Merger During Subcooled Pool Boiling of Pentane

2009 ◽  
Author(s):  
Payam Delgoshaei ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
High Speed ◽  
Pool Boiling ◽  
Side View ◽  
Time Resolved ◽  
Array Data ◽  
Earth Gravity ◽  
Microscale Heat Transfer ◽  
Line Movement

Measurements of space and time resolved heat transfer during lateral bubble merger during subcooled pool boiling of pentane in earth gravity environments were obtained using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two high-speed cameras. The heat transfer due to the lateral merger was found to be closely related to the contact line movement on the heater.

scholarly journals Pool boiling of nanofluids on biphilic surfaces

2021 ◽  
Vol 2116 (1) ◽  
pp. 012006
Author(s):  
P Pontes ◽  
E Freitas ◽  
D Fernandes ◽  
A Teixeira ◽  
R Ferreira ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Alumina Nanoparticles ◽  
Minor Role ◽  
Low Concentrations ◽  
Gold Silver ◽  
Fluid Convection ◽  
A Minor

Abstract This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions are prepared and used to act as surface interfaces with nanofluids (water with gold, silver and alumina nanoparticles) and infer on the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. The results show an evident benefice of using biphilic patterns, but with well-stablished distances between the superhydrophobic regions. Such patterns allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic surface between the superhydrophobic regions, which clearly contributes to cool down the surface. The effect of the nanofluids, for the low concentrations used here, was observed to play a minor role.

High Speed Imaging of Bubble Interface Motion in a Tapered Microgap

2020 ◽  
Author(s):  
Aranya Chauhan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
High Speed ◽  
Pool Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
Interface Motion

Abstract The current industrial trend requires development of efficient heat dissipation systems. A tapered microgap on the heater surface provides an efficient pool boiling heat transfer technique in dissipating large heat fluxes. This study is focused on capturing the high-speed images of bubble nucleation, growth and expansion processes. The interface velocities are estimated by tracking the interface of the growing bubble. The insight into interface motion will help in estimating the magnitude of the expanding force and predicting the pressure recovery effect during two-phase flow in the gap. The expansion force helps in establishing high flow rates resulting in high heat transfer coefficient (HTC) and critical heat flux (CHF) values. The effect of design parameters such as taper angle and height of the microgap on the bubble growth patterns are evaluated. The results show that the bubbles are nucleated and are then confined in the narrow gap. The tapered configuration propels the leading bubble interface in the flow direction and eventually the entire bubble in that direction. The bubble motion causes liquid to enter from the narrow region of the microgap. This effect, combined with the pressure recovery resulting from the two-phase flow in the expanding section of the microgap provides a bubble pumping mechanism. This configuration results in improving both the critical heat flux and heat transfer coefficient during pool boiling.

scholarly journals Effect of Heat Transfer on the Growing Bubble with the Nanoparticles/Water Nanofluids in Turbulent Flow

2021 ◽  
Vol 8 (1) ◽  
pp. 95-102
Author(s):  
Ahmed K. Abu-Nab ◽  
Ali F. Abu-Bakr
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Turbulent Flow ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Theoretical Data ◽  
Superheated Liquid ◽  
Two Phase ◽  
The Mathematical Model

This paper is devoted to study the effect of heat transfer on the temperature distribution in a superheated liquid during the growth of vapour bubbles immersed in different types of nanoparticles/water nanofluids between two-phase turbulent flow. The mathematical model is formulated and solved analytically depending on Scriven's theory and using the modification of the method of the similarity parameters between two finite boundaries. The characteristics of vapour bubble growth and temperature distribution are obtained by using the thermo-physical properties of nanoparticles nanofluids. The results indicate that the nanoparticle volume concentration reduces the bubble growth process under the effect of heat transfer. The better agreements are achieved, for bubble dynamics in turbulent nanofluid using the appropriate numerical and theoretical data for the values of concentration rate of nanoparticles χ=0,0.2,0.4. The temperature distribution surrounding the regime of bubble growth in pure water is more intensive than in other cases of Al2O3/H2O, Fe3O4/H2O and CuO/H2O nanofluids in turbulent flow. A Comparison of the current solution with previous works is carried out and discussed.

Nucleate Boiling Heat Transfer and Bubble Dynamics of Water-in-Polyalphaolefin Nanoemulsion

2018 ◽  
Author(s):  
Jiajun Xu ◽  
James McLaurin ◽  
Cyree Beckett
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Nucleate Boiling ◽  
Temperature History ◽  
Distribution Data ◽  
Growth Data ◽  
Surrounding Water ◽  
Time Resolved

In this study, an experimental study of the nucleation heat transfer and bubble dynamics inside the Water-in-PAO nanoemulsion fluid has been performed. Synchronized highspeed video and infrared thermography are used here to capture time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle. Data gathered included measurements of bubble growth versus time, as well as temperature history of the heater surface underneath the bubbles. Our findings demonstrate a substantial increase in nucleate heat transfer (i.e., heat transfer coefficient), and significantly different bubble dynamics of nanoemulsion fluid compared to pure water. The bubble growth rate of the nanoemulsion lies in the diffusion-controlled regime, and the growth data fit a power law at n ≈ 0.3. This is similar to the authors’ previous study of a similar fluid and is very different from conventional fluids. While the heat transfer mechanisms behind are not completely understood yet, it is hypothesized that the interfacial structures and thermal transport between surfactant molecules surrounding water nanodroplets and the base PAO fluid at elevated temperature may contribute to that.

Experimental Investigation of Nanofluid Flow Boiling in a Single Microchannel

2012 ◽  
Author(s):  
Zachary Edel ◽  
Abhijit Mukherjee
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Nanoparticle Suspension ◽  
Nanoparticle Deposition

The trends of decrease in size and increase in power dissipation for micro-electronic systems present a significant challenge for thermal management of modern electronics. The preferable cooling solution could be micro heat exchangers based on forced flow boiling. Nanoparticle deposition can affect nucleate boiling heat transfer coefficient via alteration of surface thermal conductivity, roughness, capillary wicking, wettability, and nucleation site density. It can also affect heat transfer by changing bubble departure diameter, bubble departure frequency, and the evaporation of the micro and macrolayer beneath the growing bubbles. In this study, flow boiling was investigated for 0.001 vol% aluminum oxide nanofluids in a brass microchannel and compared to results for regular water. For the case of nanofluid flow boiling, high speed images were taken after boiling durations of 25, 75, 125, and 150 min. Bubble growth rates were measured and compared for each case. Flow regime oscillation was observed and regime duration was split into two periods: single-phase liquid and two-phase. The change in regime timing revealed the effect of nanoparticle suspension and deposition on the Onset of Nucelate Boiling (ONB) and the Onset of Bubble Elongation (OBE). The addition of nanoparticles was shown to stabilize bubble growth as well as the transition of flow regimes between liquid, two-phase, and vapor.

Microscale Heat Transfer Measurements During Subcooled Pool Boiling of Pentane

2009 ◽  
Author(s):  
Payam Delgoshaei ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Pool Boiling ◽  
Superheated Liquid ◽  
Side View ◽  
Heat Transfer Mechanism ◽  
Time Resolved ◽  
Earth Gravity ◽  
Microscale Heat Transfer ◽  
Transient Conduction ◽  
Microlayer Evaporation

Measurements of space and time resolved subcooled pool boiling of pentane in earth gravity environments were made using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two highspeed cameras. The bubble growth was primarily due to energy transfer from the superheated liquid layer. Transient conduction and/or microconvection was found to be the dominant heat transfer mechanism. A composite model consisting of microlayer evaporation and transient conduction was developed and compared with the experimental data.

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