scholarly journals Heat transfer and critical heat flux for two-phase immersion cooling of an inverter power module

2021 ◽  
Vol 2116 (1) ◽  
pp. 012007
Author(s):  
I T’ Jollyn ◽  
J Nonneman ◽  
M De Paepe
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Flux Measurement ◽  
Base Plate ◽  
Heat Fluxes ◽  
Power Module ◽  
Two Phase ◽  
Heat Flux Measurement

Abstract Heat transfer and critical heat flux measurement are reported for pool boiling cooling of the base plate of an inverter power module. Novec 649 is used as refrigerant. Heat fluxes up to 14.6 W/cm2 were applied with refrigerant saturation temperatures of 36 °C, 41 °C and 46 °C. The measured boiling curves are comparable to those reported for similar refrigerants. The critical heat fluxes range from 12.1 W/cm2 to 14.6 W/cm2, which corresponds within 10% to the correlation of Zuber. The critical heat flux is significantly lower than the highest heat fluxes expected from the power module, indicating that methods to increase the critical heat flux are needed to enable two-phase power module cooling.

Heat Flux Measurement Method of Two-Phase Flow in SRM

2012 ◽  
Vol 152-154 ◽  
pp. 883-888
Author(s):  
Xiang Yu Zhang ◽  
Guo Qiang He ◽  
Pei Jin Liu ◽  
Jiang Li
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Two Phase Flow ◽  
Thermal Protection ◽  
Flux Measurement ◽  
Combustion Products ◽  
Phase Flow ◽  
Solid Rocket Motor ◽  
Two Phase ◽  
Heat Flux Measurement

Accurate information on heat transfer data of combustion products in the solid rocket motor chamber is a crucial prerequisite for the engine thermal protection. A measurement technique was well developed to acquire steady-state heat flux data of two-phase flow and was used successfully in the hostile environment. Experimental heat flux measurement has been obtained with an innovative designed instrument by simulating the flow field of complex charging configuration. The total heat flux of combustion products in the chamber was brought away by the coolant and calculated by its enthalpy rise in this device. The data could be used to analyze the heat transfer phenomena in SRMs and provide boundary condition for establishing insulation erosion model.

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 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.

Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Muhamad Zuhairi Sulaiman ◽  
Masahiro Takamura ◽  
Kazuki Nakahashi ◽  
Tomio Okawa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Flux Enhancement ◽  
Optimum Configuration ◽  
Wall Superheat ◽  
Nucleate Boiling Heat Transfer

Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40, and 60 mins. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however; in contrast effect of enhancement for downward. Maximum enhancements of CHF for upward- and downward-facing heater are 2.1 and 1.9 times, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater's BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 min which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.

Forced Convective Boiling of Refrigerant HCFC123 in a Mini-Tube

2010 ◽  
Author(s):  
Koichi Araga ◽  
Keisuke Okamoto ◽  
Keiji Murata
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Pool Boiling ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Convective Boiling ◽  
Frictional Pressure Drop ◽  
Heat Transfer Coefficients

This paper presents an experimental investigation of the forced convective boiling of refrigerant HCFC123 in a mini-tube. The inner diameters of the test tubes, D, were 0.51 mm and 0.30 mm. First, two-phase frictional pressure drops were measured under adiabatic conditions and compared with the correlations for conventional tubes. The frictional pressure drop data were lower than the correlation for conventional tubes. However, the data were qualitatively in accord with those for conventional tubes and were correlated in the form φL2−1/Xtt. Next, heat transfer coefficients were measured under the conditions of constant heat flux and compared with those for conventional tubes and for pool boiling. The heat transfer characteristics for mini-tubes were different from those for conventional tubes and quite complicated. The heat transfer coefficients for D = 0.51 mm increased with heat flux but were almost independent of mass flux. Although the heat transfer coefficients were higher than those for a conventional tube with D = 10.3 mm and for pool boiling in the low quality region, they decreased gradually with increasing quality. The heat transfer coefficients for D = 0.30 mm were higher than those for D = 0.51 mm and were almost independent of both mass flux and heat flux.

scholarly journals Determination of Pool Boiling Critical Heat Flux Enhancement in Nanofluids

2007 ◽  
Author(s):  
Bao H. Truong
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Porous Coating ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Sem Images ◽  
Heat Transfer Coefficients ◽  
Nucleate Boiling Heat Transfer

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed a CHF enhancement up to 68% and there seems to be a monotonic relationship between the nanoparticle concentration and the magnitude of enhancement. Alumina nanofluids had a CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. Scanning Electron Microscopy (SEM) images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater’s surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica.

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. Jung ◽  
S. J. Kim ◽  
J. Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
High Heat ◽  
Line Length ◽  
Boiling Curve ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Ir Camera

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

Stability and Enhancement of Boiling in Microchannels

2011 ◽  
Author(s):  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Heat ◽  
Heat Fluxes ◽  
Transfer Enhancement ◽  
The Past ◽  
The Stability ◽  
Saturated Boiling ◽  
Microelectronic Components

During the past 20 years, there has been intense worldwide interest in microchannel heat exchangers, particularly for cooling of microelectronic components. Saturated boiling of the coolant is usually indicated in order to accommodate high heat fluxes and to have uniformity of temperature. However, boiling is accompanied by several instabilities, the most severe of which can sharply limit the maximum, or critical, heat flux. These stability phenomena are reviewed, and recent studies will be discussed. Elevation of the critical heat flux will be discussed within the context of heat transfer enhancement. Means to improve the stability of boiling and the enhancement of boiling heat transfer, in general, are discussed.

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