Effects of Size of Simulated Microelectronic Chips on Boiling and Critical Heat Flux

1988 ◽  
Vol 110 (3) ◽  
pp. 728-734 ◽  
Author(s):  
K.-A. Park ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Thin Foil ◽  
Circuit Board ◽  
Boiling Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Saturated Boiling ◽  
Bottom Heater

Microelectronic chips were simulated with thin foil heaters supplied with d-c power and arranged in two vertical configurations: flush mounted on a circuit board substrate or protruding from the substrate about 1 mm. Heat transfer characteristics (midpoint) were obtained with varying height (1 mm to 80 mm) and width (2.5 mm to 70 mm) in R-113. Two types of incipient boiling temperature overshoot were observed with saturated boiling. The inception of boiling depended greatly on the location of the active boiling sites on the heater. For arrays, the inception of boiling for the top heater took place at lower superheat than for the bottom heater. Heater size had no effect on established boiling, in contrast to results reported previously in the literature. The critical heat flux for wide heaters increased with decreasing heater height, as expected. The critical heat flux also increased with decreasing width. Correlations are presented that describe these effects.

A Study of Critical Heat Flux of Butanol Aqueous Solution

2009 ◽  
Author(s):  
Shotaro Nishiguchi ◽  
Masahiro Shoji
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Surface Tension ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Heated Surface ◽  
Phase Point ◽  
Liquid Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Some alcohol aqueous solution such as butanol shows nonlinear surface tension dependence. Namely, contrary to ordinary liquid or solution, surface tension increases with temperature at the range of high liquid temperature. At the triple-phase point on a heated surface, the thermo-capillary force acts for the liquid to wet the heated surface, so the solutions are sometimes called as “self-rewetting liquid”. Self-rewetting liquids may prohibit the dry-out of a heated surface so that the heat transfer performance would be enhanced. For this reason, applications of self-rewetting liquids to heat transfer devices such as heat pipes are actively studied in recent years. However, the heat transfer characteristics of boiling of self-rewetting liquids are not fully understood. In the present research, a boiling experiment of butanol aqueous solution was performed on a heated wire in order to make clear the fundamental heat transfer characteristics, especially Critical Heat Flux (CHF), by changing solution concentration density and liquid temperature in a wide range. Bubbling aspects were observed by high-speed video camera with the rate of 1000 frames per second. It is found from the experiment that CHF is generally enhanced when compared to the case of pure water. CHF increases with concentration density at any temperatures. CHF generally increases with subcooling but at low subcooling region, it once decreases and then increases after taking a minimum. It is also found that peculiar boiling takes place where many tiny bubbles generate and bubbles are unlikely to coalesce. At high subcoolings, the mode of boiling similar to the so-called MEB (Micro-bubble Emission Boiling) was observed. These results of the present experiment indicate a possible application of butanol aqueous solution to high-performance-cooling-devices utilizing micro-channels because generating bubbles are small enough so that the pressure loss of the coolant may be small and the heat transfer rate is sufficiently high even at the saturated condition.

Heat Transfer Characteristics of Downward Facing Hot Horizontal Surfaces Using Mist Jet Impingement

2017 ◽  
Author(s):  
Ashutosh Kumar Yadav ◽  
Parantak Sharma ◽  
Avadhesh Kumar Sharma ◽  
Mayank Modak ◽  
Vishal Nirgude ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Cooling System ◽  
Water Pressure ◽  
Jet Impingement ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Impinging jet cooling technique has been widely used extensively in various industrial processes, namely, cooling and drying of films and papers, processing of metals and glasses, cooling of gas turbine blades and most recently cooling of various components of electronic devices. Due to high heat removal rate the jet impingement cooling of the hot surfaces is being used in nuclear industries. During the loss of coolant accidents (LOCA) in nuclear power plant, an emergency core cooling system (ECCS) cool the cluster of clad tubes using consisting of fuel rods. Controlled cooling, as an important procedure of thermal-mechanical control processing technology, is helpful to improve the microstructure and mechanical properties of steel. In industries for heat transfer efficiency and homogeneous cooling performance which usually requires a jet impingement with improved heat transfer capacity and controllability. It provides better cooling in comparison to air. Rapid quenching by water jet, sometimes, may lead to formation of cracks and poor ductility to the quenched surface. Spray and mist jet impingement offers an alternative method to uncontrolled rapid cooling, particularly in steel and electronics industries. Mist jet impingement cooling of downward facing hot surface has not been extensively studied in the literature. The present experimental study analyzes the heat transfer characteristics a 0.15mm thick hot horizontal stainless steel (SS-304) foil using Internal mixing full cone (spray angle 20 deg) mist nozzle from the bottom side. Experiments have been performed for the varied range of water pressure (0.7–4.0 bar) and air pressure (0.4–5.8 bar). The effect of water and air inlet pressures, on the surface heat flux has been examined in this study. The maximum surface heat flux is achieved at stagnation point and is not affected by the change in nozzle to plate distance, Air and Water flow rates.

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