Experimental Study of a Two-Phase Thermosyphon With Porous Graphite Foam Insert

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
L. W. Jin ◽  
K. C. Leong ◽  
I. Pranoto ◽  
H. Y. Li ◽  
J. C. Chai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Working Fluid ◽  
Two Phase ◽  
Filling Volume ◽  
Porous Graphite ◽  
Surface Tension Forces ◽  
Graphite Foam

This paper presents an experimental study of heat transfer in a pool boiling evaporator with porous insert. Porous graphite foams were structured into cubic block and straight fin shapes and tested with FC-72 and HFE-7000 coolants with the objective of maximizing the heat transfer in a pool boiling configuration. A two-phase thermosyphon facility was developed to investigate the system’s performance using graphite foams of block and fin structures. The effects of foam configuration, working fluid type, and coolant filling volume on pool boiling heat transfer were analyzed. The results showed that the coolant filling volume has negligible effect on cooling performance. On the other hand, the thermosyphon performance is significantly affected by the coolant properties and the configuration of the porous graphite foam. A comparison of the Bond numbers obtained for FC-72 and HFE-7000 indicates that the bubbles have to overcome higher surface tension forces before departing the foam surface in HFE-7000. Meanwhile, the effect of the foam configuration on the boiling heat transfer performance implies that a properly designed geometry of the porous graphite foam will lead to significant enhancement of the evaporation process in a thermosyphon system.

Experimental Study of a Two-Phase Thermosyphon With Porous Graphite Foam Insert

2010 ◽  
Author(s):  
K. C. Leong ◽  
L. W. Jin ◽  
I. Pranoto ◽  
H. Y. Li ◽  
J. C. Chai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Working Fluid ◽  
Two Phase ◽  
Filling Volume ◽  
Porous Graphite ◽  
Surface Tension Forces ◽  
Graphite Foam

This paper presents an experimental study of heat transfer in a pool boiling evaporator with porous insert. Porous graphite foams of different structures were tested with FC-72 and HFE-7000 coolants with the objective of maximizing the heat transfer in a pool boiling configuration. A two-phase thermosyphon facility was developed to investigate the system performance using graphite foams of block and fin structures. The effects of foam configuration, working fluid type and coolant filling volume on heater surface temperature and superheat were analyzed. The results showed that coolant filling volume has negligible effect on the cooling performance. On the other hand, the thermosyphon performance is significantly affected by the coolant properties and the configuration of the porous graphite foam. A comparison of the Bond numbers obtained for FC-72 and HFE-7000 indicates that the bubbles have to overcome higher surface tension forces before departing the foam surface in HFE-7000. Meanwhile, the effect of foam configuration on the boiling heat transfer performance implies that a properly designed geometry of porous graphite foam will lead to significant enhancement of the evaporation process in a thermosyphon system.

Experimental Study of Enhanced Pool Boiling Heat Transfer Using Graphite Foam Inserts

2011 ◽  
Vol 312-315 ◽  
pp. 352-357 ◽  
Author(s):  
K.C. Leong ◽  
L.W. Jin ◽  
I. Pranoto ◽  
H.Y Li ◽  
J.C. Chai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Bubble Formation ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Copper Block ◽  
Different Types ◽  
Graphite Foam

This paper presents the results of an experimental study of heat transfer in a pool boiling evaporator with porous insert. Different types of graphite foams were tested with the phase change coolant FC-72 in a designed thermosyphon. Comparisons between the graphite foams and a solid copper block show that the porous structure enhances pool boiling significantly. The boiling thermal resistance of the tested graphite foams was found to be about 2 times lower than that of the copper block. The bubble formation recorded by a high speed camera indicates that boiling from a graphite foam is more vigorous than from a copper block. The designed thermosyphon with graphite foam insert can remove heat fluxes of up to 112 W/cm2 with the maximum heater temperature maintained below 100°C.

Experimental Study of Subcooled Pool Boiling Heat Transfer on Metal Foam

2011 ◽  
Author(s):  
Juan Shi ◽  
Anthony M. Jacobi ◽  
Zhenqian Chen
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Boiling Heat Transfer ◽  
Metal Foam ◽  
Pool Boiling ◽  
Metal Foams ◽  
Working Fluid ◽  
Maximum Heat ◽  
Pool Boiling Heat Transfer

The present experimental study is focused on subcooled pool boiling heat transfer on aluminum metal foam at atmospheric pressure. Experiments are conducted with open-cell metal foam of different porosity and different thickness, using water as the working fluid. The surface superheat ranges up to 15 °C, with maximum heat flux of about 30 W/cm2. The thermal performance of pool boiling on metal foams is compared to that on a roughened copper surface of the same dimensions. The thickness and the geometry of metal foams significantly influence the pool boiling heat transfer coefficient. The effect of orientation on the thermal performance in metal foam is also studied. The surface temperature excursion at boiling incipience and small hysteresis is observed in the experiments. When the metal foam thickness is reduced, hysteresis becomes more significant.

scholarly journals Effect of Nanofluids on the Enhancement of Boiling Heat Transfer: A Review

2021 ◽  
Vol 6 (4) ◽  
pp. 259-283
Author(s):  
Md. Osman Ali ◽  
Mohammad Zoynal Abedin ◽  
Md. Dulal Ali ◽  
Mohammad Rasel Rasel
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Pool Boiling ◽  
Working Fluid ◽  
Two Phase ◽  
Enhancement Of Heat Transfer ◽  
Passive Techniques

Boiling heat transfer can play a vital role in the two-phase flow applications. The analysis of the boiling hat transfer enhancement is of importance in such applications and the enhancement can be mostly conducted by using various active and passive techniques. One type of passive techniques is the enhancement of heat transfer by nanofluids. This article presents an extensive review on the effect of different nanofluids on the enhancement of heat transfer coefficient (HTC) and critical heat flux (CHF) for both pool as well as flow boiling. Nanoparticles addition to a working fluid is done arbitrarily to improve the thermophysical properties which in turn improves heat transfer rate. Numerous works have been done in the studies on nanofluid boiling. Among various nanoparticles, the most frequently used nanoparticles are Al2O3 and TiO2. In the case of binary nanoparticles, the most commonly used combination is Al2O3 and TiO2. After reviewing the relevant literatures, it is found that for pool boiling, the maximum HTC is increased to 138% for TiO2 nanoparticles and the maximum CHF is increased to 274.2% for MWCNTs. Conversely, in flow boiling the maximum HTC is increased to 126% for ZnO nanoparticles and the maximum CHF increased to as 100% for GO nanoparticles. In addition, when two or more nanoparticles in succession or binary nanofluids are used the CHF in pool boiling increased up to 100% for Al2O3 and TiO2 as well as the CHF in flow boiling increased up to 100% for Al2O3, ZnO, and Diamond. Though the information of the coefficient of heat transfer and the critical heat flux varied for different nanofluids and vary from experiment to experiment for each of the nanofluids. This variation happens because the coefficient of heat transfer and the critical heat flux in boiling is dependent upon several factors.

Experimental Verification of Analytical Prediction of Pool Boiling CHF Incorporating the Effects of EHD and Contact Angle

2015 ◽  
Author(s):  
Ichiro Kano ◽  
Takahiro Sato ◽  
Naoki Okamoto
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Electric Field ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Contact Angles ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Analytical Prediction ◽  
Compound Effect

Boiling heat transfer enhancement via compound effect of Electro-Hydro-Dynamic (EHD) and contact angle has been experimentally and analytically investigated. A fluorinated dielectric liquid (Asahi Glass Co. Ltd, AE-3000) was selected as the working fluid. Pool boiling heat transfer in the saturated liquid was measured at atmospheric pressure. In order to change the contact angle between the boiling surface and the dielectric liquid, the different materials Cu, Cr, NiB, Sn, and mixture of 5 and 1.5 micro meter diamond particles were electrically deposited on a boiling surface. The critical heat flux (CHF) for different contact angles showed 20.5 ∼ 26.9 W/cm2 which was −7 ∼ 25 % of that for a non-coated Cu surface (21.5 W/cm2). Upon application of a −5 kV/mm electric field to the micro structured surface (the mixture of 5 and 1.5 micro meter particles), a CHF of 99 W/cm2 at a superheat of 33.5 K was obtained. The previous theoretical equation of pool boiling predicted the CHF with the electric field and without the electrode.

Sign in / Sign up

Export Citation Format

Share Document