Heat Transfer Characteristics in Mist Cooling With Machining Oil

2005 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Tomoyasu Tanaki ◽  
Yasuo Koizumi
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heated Surface ◽  
Water Mist ◽  
Transfer Mechanism ◽  
Heat Transfer Mechanism ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Oil Mist ◽  
Mist Cooling

Heat transfer characteristics in mist cooling with commercial machining oil were investigated experimentally. Steady state experiments of heat transfer were conducted using a pure copper cylinder and mist flow of commercial machining oil and air. Liquid flow rate was 0.3, 0.9, 1.8, 4 and 8 l/hr, respectively; each air flow rate was 0, 40, 75 and 120 lN/min. Furthermore, liquid mass flux on the heating surface for each experimental condition was measured by using a measuring cylinder with same diameter as the heater. Average velocity of droplets and average diameter of those were measured by using a laser doppler anemometer and immersion method, respectively. The heat transfer mechanism in oil mist was only cooling of liquid film formed on a heated surface, whereas the heat transfer mechanism in water mist cooling was classified into three regions. The heat transfer coefficient in the oil mist was well expressed by the heat removal capacity on sensible heat of supplying oil-droplets to the heated surface. Four dimensionless correlations were derived from a dimension analysis, Buckingham Pi theorem, and experimental data for both water mist and the oil mist.

scholarly journals Numerical Investigation on the Influence of Surface Flow Direction on the Heat Transfer Characteristics in a Granite Single Fracture

2021 ◽  
Vol 11 (2) ◽  
pp. 751
Author(s):  
Xuefeng Gao ◽  
Yanjun Zhang ◽  
Zhongjun Hu ◽  
Yibin Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Flow Direction ◽  
Heat Extraction ◽  
Geothermal System ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transfer Capacity

As fluid passes through the fracture of an enhanced geothermal system, the flow direction exhibits distinct angular relationships with the geometric profile of the rough fracture. This will inevitably affect the heat transfer characteristics in the fracture. Therefore, we established a hydro-thermal coupling model to study the influence of the fluid flow direction on the heat transfer characteristics of granite single fractures and the accuracy of the numerical model was verified by experiments. Results demonstrate a strong correlation between the distribution of the local heat transfer coefficient and the fracture morphology. A change in the flow direction is likely to alter the transfer coefficient value and does not affect the distribution characteristics along the flow path. Increasing injection flow rate has an enhanced effect. Although the heat transfer capacity in the fractured increases with the flow rate, a sharp decline in the heat extraction rate and the total heat transfer coefficient is also observed. Furthermore, the model with the smooth fracture surface in the flow direction exhibits a higher heat transfer capacity compared to that of the fracture model with varying roughness. This is attributed to the presence of fluid deflection and dominant channels.

Study on Boiling Heat Transfer and Critical Heat Flux in Mist Cooling: Effect of Droplet Size on Heat Transfer Characteristics

2004 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Tomoyasu Tanaki ◽  
Yasuo Koizumi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Droplet Size ◽  
Flow Rate ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Liquid Mass ◽  
Mist Cooling

Boiling heat transfer and critical heat flux—CHF—in mist cooling were investigated experimentally and analytically. Especially, the heat transfer in the mist cooling was examined focusing on the effects of droplet size and droplet velocity on the heat transfer characteristics. Steady state experiments of heat transfer were conducted using a pure copper cylinder and mist flow of water-air at room temperature. Liquid flow rate was 0.3, 0.9, 1.8, 4 and 8 l/hr, respectively; each air flow rate on normal condition was 0, 40, 75 and 120 lN/min. Furthermore, liquid mass flux on the heater surface for each experimental condition was measured by using a cylinder with a scale and the same diameter as the heater. Distribution of air velocity, average velocity of droplets and average diameter of droplets were measured by using a fine Pitot tube, laser doppler anemometry and immersion method, respectively. Three correlations of the mist cooling rate for non-boiling, evaporation of droplets and evaporation of the liquid film were developed by using the measured liquid mass flux, characteristic droplet velocity and wall superheat. A CHF model was presented by focusing on maximum evaporation rate of the liquid mass flux on a heater. A droplet evaporation model was proposed by using the transient heat conduction in a sphere. Finally, three dimensionless correlations for the mist cooling were presented.

Heat Transfer Characteristics during Mist Cooling on a Heated Cylinder

2005 ◽  
Vol 26 (8) ◽  
pp. 24-31 ◽  
Author(s):  
Sookwan Lee ◽  
Jeeman Park ◽  
Piljong Lee ◽  
Moohwan Kim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Heated Cylinder ◽  
Transfer Characteristics ◽  
Mist Cooling

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.

scholarly journals Heat transfer in a novel microwave heating device coupled with atomization feeding

2021 ◽  
pp. 288-288
Author(s):  
Shangzhi Yu ◽  
Qinglong Xie ◽  
Xiaoning Mao ◽  
Ying Duan ◽  
Yong Nie
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
High Temperature ◽  
Microwave Heating ◽  
Flow Rate ◽  
Orifice Diameter ◽  
Spray Parameters ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Spray Flow Rate

The heat transfer characteristics of the microwave heating coupled with atomization feeding were investigated using ethanol as the spray medium on a pressure swirl nozzle. The effects of spray height, flow rate and temperature on the sauter mean diameter (SMD) of atomized droplets were examined. The results showed that the droplet SMD was 12-130 ?m, which increased with the spray height and decreased with the flow rate and temperature of spray medium. Through the fitting of the experimental data, the dimensionless correlation of the droplet SMD which was based on orifice diameter, Reynolds and Ohnesorge numbers was obtained. The calculated results were basically consistent with the experimental data within 15% error. The heat transfer characteristics of atomized droplets on high-temperature surface of SiC bed heated by microwave were then investigated. The effects of spray flow rate, spray height and spray temperature on the heat transfer characteristics were examined. The power of spray heat transfer decreased with the temperature and increased with the spray flow rate and spray height. The dimensionless correlation to describe the heat transfer characteristics of atomized droplets on the high-temperature SiC surface under the microwave heating was obtained which included thermophysical properties of spray medium, spray parameters, and temperatures of the high-temperature bed surface and spray medium, with the error of ?20%. These correlations can be used to predict the SMD of the atomized droplets and the power of spray heat transfer in the microwave heating process.

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