A method for improving two-dimensional high heat flux estimates from surface temperature measurements

1997 ◽  
Author(s):  
D. Walker ◽  
Elaine Scott ◽  
D. Walker ◽  
Elaine Scott
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
High Heat ◽  
Temperature Measurements ◽  
High Heat Flux ◽  
Two Dimensional

scholarly journals R&D on divertor plasma facing components at the Institute for Plasma Research

Nukleonika ◽  
2015 ◽  
Vol 60 (2) ◽  
pp. 285-288 ◽  
Author(s):  
Yashashri Patil ◽  
S. Khirwadkar ◽  
S. M. Belsare ◽  
Rajamannar Swamy ◽  
M. S. Khan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Infrared Thermography ◽  
High Heat ◽  
High Heat Flux ◽  
Acceptance Criteria ◽  
Plasma Facing Components ◽  
Type Test ◽  
Plasma Research

Abstract This paper is focused on various aspects of the development and testing of water cooled divertor PFCs. Divertor PFCs are mainly designed to absorb the heat and particle fluxes outflowing from the core plasma of fusion devices like ITER. The Divertor and First Wall Technology Development Division at the Institute for Plasma Research (IPR), India, is extensively working on development and testing of divertor plasma facing components (PFCs). Tungsten and graphite macro-brush type test mock-ups were produced using vacuum brazing furnace technique and tungsten monoblock type of test mock-ups were obtained by hot radial pressing (HRP) technique. Heat transfer performance of the developed test mock-ups was tested using high heat flux tests with different heat load conditions as well as the surface temperature monitoring using transient infrared thermography technique. Recently we have established the High Heat Flux Test Facility (HHFTF) at IPR with an electron gun EH300V (M/s Von Ardenne Anlagentechnik GmbH, Germany) having maximum power 200 kW. Two tungsten monoblock type test mock-ups were probed using HHFTF. Both of the test mock-ups successfully sustained 316 thermal cycles during high heat flux (HHF) tests. The test mock-ups were non-destructively tested using infrared thermography before and after the HHF tests. In this note we describe the detailed procedure used for testing macro-brush and monoblock type test mock-ups using in-house transient infrared thermography set-up. An acceptance criteria limit was defined for small scale macro-brush type of mock-ups using DTrefmax value and the surface temperature measured during the HHF tests. It is concluded that the heat transfer behavior of a plasma facing component was checked by the HHF tests followed by transient IR thermography. The acceptance criteria DTrefmax limit for a graphite macro-brush mock-up was found to be ~3°C while for a tungsten macro-brush mock-up it was ~5°C.

Prediction of Refrigerant Flow Boiling Hysteresis With an Augmented Separated-Flow Model

2016 ◽  
Author(s):  
Jianwei Gao ◽  
Hongxia Li ◽  
Saif Almheiri ◽  
TieJun Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Flow Model ◽  
Flow Boiling ◽  
Separated Flow ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Boiling Hysteresis

Thermal management is essential to compact devices particularly for high heat flux removal applications. As a popular thermal technology, refrigeration cooling is able to provide relatively high heat flux removal capability and uniform device surface temperature. In a refrigeration cycle, the performance of evaporator is extremely important to the overall cooling efficiency. In a well-designed evaporator, effective flow boiling heat transfer can be achieved whereas the critical heat flux (CHF) or dryout condition must be avoided. Otherwise the device surface temperature would rise significantly and cause device burnout due to the poor heat transfer performance of film boiling. In order to evaluate the influence of varying imposed heat fluxes, saturated flow boiling in the evaporator is systematically studied. The complete refrigerant flow boiling hysteresis between the imposed heat flux and the exit wall superheat is characterized. Upon the occurrence of CHF at the evaporator wall exit, the wall heat flux redistributes due to the axial wall heat conduction, which drives the dryout point to propagate upstream in the evaporator. As a result, a significant amount of thermal energy is stored in the evaporator wall. While the heat flux starts decreasing, the dryout point moves downstream and closer to the exit. The stored heat in the wall dissipates slowly and leads to the delay in rewetting or quenching, which is the key to understand and predict the flow boiling hysteresis. In order to reveal the transient heat releasing mechanism, an augmented separated-flow model is developed to predict the moving rewetting point and minimum heat flux at the evaporator exit, and the model predictions are further validated by experimental data from a refrigeration cooling testbed.

Flow Excursion-Induced Dryout at Low Heat Flux Natural Convection Boiling

1986 ◽  
Vol 108 (2) ◽  
pp. 425-432 ◽  
Author(s):  
M. Khatib-Rahbar ◽  
E. G. Cazzoli
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Natural Convection ◽  
High Heat ◽  
High Heat Flux ◽  
Two Dimensional ◽  
Boiling Process ◽  
Fast Breeder Reactors ◽  
Breeder Reactors ◽  
Saturated Boiling

Flow excursion-induced dryout at low heat flux natural convection boiling, typical of liquid metal fast breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of the Ledinegg instability, leading to flow excursion and subsequent dryout in agreement with experimental data. A flow regime-dependent critical heat flux relationship based upon a saturated boiling criterion is also presented. Transient analyses indicate that premature flow excursion cannot be ruled out and the boiling process is transient dependent. Analysis of a loss-of-flow transient at high heat flux forced convection shows a significantly faster flow excursion leading to dryout, which is in excellent agreement with the results of the two-dimensional THORAX code.

Immersion Cooling of Power Electronics in Segregated Hydrofluoroether Liquids

2008 ◽  
Author(s):  
Cindy M. Barnes ◽  
Phil E. Tuma
Keyword(s):  
Heat Flux ◽  
High Heat ◽  
Temperature Measurements ◽  
Junction Temperature ◽  
Published Data ◽  
High Heat Flux ◽  
Two Phase ◽  
Maximum Heat ◽  
Dielectric Liquids ◽  
Immersion Cooling

Passive two-phase immersion cooling with dielectric liquids is a well established method of cooling thyristor type power semiconductors. However, the capabilities of this method for cooling high heat flux power semiconductor devices such as insulated gate bipolar transistors (IGBTs) have not been thoroughly explored. This work quantifies the junction-to-fluid thermal resistance of IGBTs soldered to boilers and immersed in the segregated hydrofluoroether liquid C3F7OCH3, one of a class of new dielectric liquids with a low Global Warming Potential. The boilers were square copper heat spreaders with a microporous metallic boiling enhancement coating applied to the wetted surfaces. Bare 0.54cm2 IGBT die were soldered to experimentally-optimized boilers and immersed in saturated C3F7OCH3 liquid at atmospheric pressure. Boiler temperature measurements showed a peak boiler-to-fluid heat transfer coefficient of ∼14W/cm2-K at a die level heat flux of 255 W/cm2. Direct junction temperature measurements yielded junction-to-fluid resistivities of 0.15°C/(W/cm2) at this heat flux and 0.20°C/(W/cm2) at 400 W/cm2, the maximum heat flux studied. These results, coupled with published data for air cooled condensers, show that passive two-phase cooling of power modules may provide junction-to-ambient thermal resistances approximately 25% those of conventional air cooled modules and junction-to-fluid resistances 30%–50% of conventional liquid cooled modules, and similar to emerging direct substrate liquid cooling schemes.

Effects of High Frequency Droplet Train Impingement on Spreading-Splashing Transition, Film Hydrodynamics and Heat Transfer

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Taolue Zhang ◽  
Jorge Alvarado ◽  
J. P. Muthusamy ◽  
Anoop Kanjirakat ◽  
Reza Sadr
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Liquid Film ◽  
High Frequency ◽  
High Heat ◽  
High Heat Flux ◽  
Droplet Impingement ◽  
Dry Out ◽  
The Impact

The objective of this study is to investigate the effects of droplet-induced crown propagation regimes (spreading and splashing) on liquid film hydrodynamics and heat transfer. In this work, the effects of high frequency droplet train impingement on spreading-splashing transition, liquid film hydrodynamics and surface heat transfer were investigated experimentally. HFE-7100 droplet train was generated using a piezo-electric droplet generator at a fixed flow rate of 165 mL/h. Optical and IR images were captured at stable droplet impingement conditions to visualize the thermal physical process. The droplet-induced crown propagation transition phenomena from spreading to splashing were observed by increasing the droplet Weber number. The liquid film hydrodynamics induced by droplet train impingement becomes more complex when the surface was heated. Bubbles and micro-scale fingering phenomena were observed outside the impact crater under low heat flux conditions. Dry-out was observed outside the impact craters under high heat flux conditions. IR images of the heater surface show that heat transfer was most effective within the droplet impact crater zone due to high fluid inertia including high radial momentum caused by high-frequency droplet impingement. Time-averaged heat transfer measurements indicate that the heat flux-surface temperature curves are linear at low surface temperature and before the onset of dry-out. However, a sharp increase in surface temperature can be observed when dry-out appears on the heater surface. Results also show that strong splashing (We = 850) is unfavorable for heat transfer at high heat flux conditions due to instabilities of the liquid film, which lead to the onset of dry-out. In summary, the results show that droplet Weber number is a significant factor in the spreading-splashing transition, liquid film hydrodynamics and heat transfer.

Visualization Research on Heat Pipe Radiator in Cooling Electronic Apparatus with High Heat Flux

2011 ◽  
Vol 105-107 ◽  
pp. 1880-1884
Author(s):  
Zhong Chao Zhao ◽  
Rui Ye ◽  
Yu Ping Chen ◽  
Gen Ming Zhou
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Electronic Device ◽  
High Heat ◽  
High Heat Flux ◽  
Thermal Imager ◽  
Electronic Apparatus ◽  
Fan Speed ◽  
Infrared Thermal Imager

In this paper, the heat transfer characters of heat pipe radiator for cooling electronic device with high heat flux were investigated by visualization method. The surface temperature of heat pipe radiator was measured at different heat flux and constant fan speed of 0.7m/s, and the results show that the surface temperature of electronic apparatus is below 75°C for the heat flux 8W/cm2 at constant fan speed of 0.7m/s; The error in measured value using thermocouple and technique of infrared thermography was analyzed based on the principles of temperature measurement of infrared thermal imager.

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