Experimental study of thermal limits with one-side heated smooth channel for plasma facing component safety

2021 ◽  
Author(s):  
Ji Hwan Lim ◽  
Minkyu Park
Keyword(s):  
Heat Flux ◽  
Flow Instability ◽  
Load Condition ◽  
High Heat ◽  
Error Rates ◽  
Thermal Engineering ◽  
High Heat Flux ◽  
System Pressure ◽  
Smooth Channel ◽  
Micro Channels

Abstract In order to stably operate the equipment inside the tokamak, which is loaded with a heat flux of several MW/m2 under the one-side heating condition, it is necessary to thoroughly prepare for various thermal engineering limits that may occur under the high heat flux load condition. In this study, we have experimentally explored critical heat flux (CHF) and onset of flow instability (OFI), which are considered potential threats in a DEMO fusion power plant. Specifically, the effect of system parameters on CHF was investigated. The results indicate that with an increase in subcooling and mass flux, the CHF increased, as it induced a faster bubble condensation near the CHF. As the system pressure increased, the CHF also increased. This is because the bubble size reduction effect was dominant in the pressure range of 1–10 bar. Most of the existing CHF correlations could evaluate the CHF with reasonable accuracy of within 25%; especially, the Boscary CHF correlation yielded the highest accuracy with an average error of 12%. Similar to CHF, OFI, which is a measure of the sudden fluctuations in the system pressure caused by a large amount of vapor generated due to the high heat flux, tended to increase as the subcooling, mass flow rate, and system pressure increased. Most of the existing OFI correlations yielded large error rates (more than 135%) as these correlations were primarily developed for micro-channels. Therefore, in this study, a new OFI correlation was developed using a Python code, in combination with an artificial intelligence (AI) regression method. The developed correlation can be used in the cooling system design of tokamaks, which involve a high-heat load condition on one-side of the reactor.

Micro Heat Changers and Surface-Micro-Coolers for High Heat Flux

2008 ◽  
Author(s):  
Ulrich Schygulla ◽  
Ju¨rgen J. Brandner ◽  
Eugen Anurjew ◽  
Edgar Hansjosten ◽  
Klaus Schubert
Keyword(s):  
Heat Flux ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Pressure Loss ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Micro Heat Exchanger ◽  
Micro Channels ◽  
Higher Temperature

This publication describes the development of a new microstructure to transfer high heat fluxes. With a simple mathematical model based on heat conduction theory for the heat transfer in a micro channel at laminar flow conditions it was deduced that for the transmission of high heat fluxes only the initial part at the beginning of the micro channels is of importance, i.e. the micro channels should be short. Based on this principle a micro structure was designed with a large number of short micro channels taken in parallel. With this newly developed microstructure a prototype of a micro heat exchanger and a surface micro cooler was manufactured and tested. Using the prototype of the micro heat exchanger, manufactured of plastic, heat fluxes up to 500 W/cm2 were achieved at a pressure loss of 0.16 MPa and a mass flow of the water of 200 kg/h per passage. Due to the use of materials with a higher temperature resistance and higher stability like aluminum or ceramic, higher water throughputs and higher flow velocities could be realized in the micro channels. Thus it was possible to increase the heat flux up to approx. 800 W/cm2 at a pressure loss of approx. 0.35 MPa and a mass flow of 350 kg/h per passage. The important focus of investigation of the surface micro cooler was set on the examination of the surface temperatures for different heat fluxes and different velocities of the water in the micro channels. The experimental results of these surface micro coolers are summarized to characteristic maps. With this characteristic maps it is possible to determine whether a micro surface cooler can be used for a specific application.

A Microstructure Device for Single Phase Surface Cooling

2011 ◽  
Author(s):  
Juergen J. Brandner ◽  
Natrah binti Kamaruzaman ◽  
Stefan Maikowske
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Single Phase ◽  
High Heat ◽  
Theoretical Background ◽  
Test Facility ◽  
Fluid Distribution ◽  
High Heat Flux ◽  
Surface Cooling ◽  
Micro Channels

A microstructure device for cooling of hot surfaces at liquid single phase laminar flow is presented. The initial design as well as the theoretical background is described in detail. It consists of numerous short micro channels acting as overflow structures and providing a relatively large hydraulic diameter, used in parallel between large inlet and outlet channels. The design was chosen to be scalable as well as appropriate for mass production in different materials. The fluid distribution was optimized as well as the dimensions of the overflow structures in terms of heat transfer, both by CFD simulations. Several devices were tested. They provide very high heat flux at reasonably low pressure drop. The temperature difference to achieve, heat flux and pressure drop can be adjusted easily by control of the applied mass flow. The design was tested as liquid-liquid heat exchanger in a simple lab-scale test facility. Moreover, using a copper electrically powered surface heat focus, some devices were tested as surface coolers.

scholarly journals Prospects for using two-phase micro-size systems for high heat flux removal

2021 ◽  
Vol 2057 (1) ◽  
pp. 012058
Author(s):  
V V Kuznetsov ◽  
A S Shamirzaev ◽  
A S Mordovskoy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Micro Channel ◽  
Copper Target ◽  
Jet Cooling ◽  
Micro Channels

Abstract Heat transfer in active systems for high heat removal based on the micro-channels and hybrid micro-channel/micro-jet is considered. The application of these systems allows significantly increasing the critical heat flux for a dense arrangement of the heat stressed equipment. The characteristics of heat transfer and critical heat flux during subcooled flow boiling of water in the micro-channel heat sink and during micro-jet impingement in narrow channel are obtained. The experiments are performed for the horizontal segmented microchannels with a cross section of 340×2000 μm2 made on the top of copper target and for impingement micro-jet cooling of the copper target in the gap of 1000 μm. It has been found that, compared with impingement micro-jet cooling in similar condition, the micro-channel cooling is more effective for high heat flux removal although it creates the considerably high wall temperature.

High heat flux cooling of accelerator targets with micro-channels

2006 ◽  
Vol 562 (2) ◽  
pp. 903-905 ◽  
Author(s):  
Hanoch Hirshfeld ◽  
Ido Silverman ◽  
Alexander Arenshtam ◽  
Dany Kijel ◽  
Ami Nagler
Keyword(s):  
Heat Flux ◽  
High Heat ◽  
High Heat Flux ◽  
Micro Channels
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