Tissue responses to fractional transient heating with sinusoidal heat flux condition on skin surface

2016 ◽  
Vol 87 (10) ◽  
pp. 1304-1311 ◽  
Author(s):  
Magdy A. Ezzat ◽  
Alaa A. El-bary ◽  
Noorah S. Al-sowayan
Keyword(s):  
Heat Flux ◽  
Skin Surface ◽  
Transient Heating ◽  
Flux Condition ◽  
Tissue Responses

Flow Behavior and Flow Boiling Heat Transfer in Thin-Rectangular Mini-Channels

2008 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Tomonari Yamada
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Pattern ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Annular Flow ◽  
Flow Channel ◽  
Heat Transfer Surface ◽  
Liquid Slug ◽  
Flux Condition

Boiling heat transfer of thin-rectangular channels of the width of 10 mm has been examined. The height of the flow channel was in a range from 0.6 mm to 0.4 mm. Experimental fluid was water. Bubbly flow, slug flow, semi annular flow and annular flow were observed. The flow pattern transition agreed well with the Baker flow pattern map for the usual sized flow path. The critical heat flux was lower than the value of the usual sized flow channel. The Koizumi and Ueda method predicted well the trend of the critical heat flux of the present experiments. At the critical heat flux condition, the heat transfer surface was covered by liquid slug, a large bubble pushed away the liquid slug, a dry area was formed on the heat transfer surface and then liquid slug came around to cover the heat transfer surface again. This process repeated rapidly. Following this observation, a heat transfer surface temperature calculation model at the critical heat flux condition was proposed. The calculated result re produced the experimental result.

Rotating flow of carbon nanotubes subject to prescribed heat flux condition

2020 ◽  
Vol 96 (2) ◽  
pp. 025217
Author(s):  
Tasawar Hayat ◽  
Farwa Haider ◽  
Taseer Muhammad ◽  
Ahmed Alsaedi
Keyword(s):  
Carbon Nanotubes ◽  
Heat Flux ◽  
Rotating Flow ◽  
Flux Condition

Dryout Avoidance Control for Multi-Evaporator Vapor Compression Cycles With Transient Heat Flux

2014 ◽  
Author(s):  
Daniel T. Pollock ◽  
Zehao Yang ◽  
John T. Wen
Keyword(s):  
Heat Flux ◽  
Flow Rate ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
High Heat Flux ◽  
Vapor Compression ◽  
Transient Heating ◽  
Outer Loop ◽  
Two Phase ◽  
Loop Control

Multiple-evaporator vapor compression cycles may be used for distributed cooling of high heat-flux systems, such as arrays of high-power electronics. Under transient heating conditions, these systems must be carefully controlled to avoid critical heat flux (CHF) due to evaporator dryout. An active control strategy is presented that regulates two-phase flow quality in multiple evaporators in order to avoid critical quality under transient heating conditions. A two-loop control system is used, in which an outer loop uses model-based feedforward combined with evaporator wall temperature feedback to determine the necessary coolant flow rate to avoid CHF, while an inner loop uses system actuators (variable speed compressor, electronic expansion valves) to track to the desired flow rate. An advantage of this approach is that the inner-loop control handles the system complexity arising from pressure coupling and actuator nonlinearity. Additionally, the outer-loop quality control may be applied to other two-phase cooling schemes, for instance pumped systems, by providing coolant flow rate setpoints. Simulations and corresponding experimental controller validation were conducted using a three-evaporator vapor compression testbed with transient imposed heat-flux.

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