scholarly journals Ultrasounds Used as Promoters of Heat-Transfer Enhancement of Natural Convection in Dielectric Fluids for the Thermal Control of Electronic Equipment

Acoustics ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 279-292
Author(s):  
Carlo Bartoli ◽  
Alessandro Franco ◽  
Massimo Macucci
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Enhancement Effect ◽  
Electronic Board ◽  
Experimental Apparatus

We present an experimental investigation of the effect of ultrasound application to increase the heat-transfer coefficient for natural convection of a dielectric fluid. An experimental analysis is carried out to estimate the increase of the convective heat-transfer coefficient between an electronic board and a refrigerant fluid, the Fluorinert Electronic Fluid FC-72. For this purpose, an experimental apparatus composed of an electronic board, its electronic control circuit, and data acquisition systems have been designed and implemented. The data collected appear to confirm in some situations of practical interest the enhancement effect of the convective heat-transfer coefficient in connection with the use of ultrasound. The most favorable condition was observed with the fluid in quite low subcooled conditions.

Investigations on Transient Natural Convection in Boron Nitride-Mineral Oil Nanofluid Systems

2012 ◽  
Author(s):  
Shijo Thomas ◽  
C. B. Sobhan ◽  
Jaime Taha-Tijerina ◽  
T. N. Narayanan ◽  
P. M. Ajayan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Boron Nitride ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Mineral Oil

Nanofluids are suspensions or colloids produced by dispersing nanoparticles in base fluids like water, oil or organic fluids, so as to improve their thermo-physical properties. Investigations reported in recent times have shown that the addition of nanoparticles significantly influence the thermophysical properties, such as the thermal conductivity, viscosity, specific heat and density of base fluids. The convective heat transfer coefficient also has shown anomalous variations, compared to those encountered in the base fluids. By careful selection of the parameters such as the concentration and the particle size, it has been possible to produce nanofluids with various properties engineered depending on the requirement. A mineral oil–boron nitride nanofluid system, where an increased thermal conductivity and a reduced electrical conductivity has been observed, is investigated in the present work to evaluate its heat transfer performance under natural convection. The modified mineral oil is produced by chemically dispersing boron nitride nanoparticles utilizing a one step method to obtain a stable suspension. The mineral oil based nanofluid is investigated under transient free convection heat transfer, by observing the temperature-time response of a lumped parameter system. The experimental study is used to estimate the time-dependent convective heat transfer coefficient. Comparisons are made with the base fluid, so that the enhancement in the heat transfer coefficient under natural convection situation can be estimated.

Heat Transfer Enhancement by Ultrasound Pressure Waves in Liquid Water: A Cooling Method for New Electronic Components

2014 ◽  
Vol 556-562 ◽  
pp. 1968-1974
Author(s):  
Carlo Bartoli ◽  
F. Baffigi ◽  
Andrea Brunini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Ultrasonic Waves ◽  
Ultrasonic Power ◽  
Experimental Apparatus

The objective of this work is to study the increase of the convective heat transfer coefficient in the presence of ultrasound waves and, in particular, to find a relationship between the ultrasonic power and the effective pressure of water. The tests have focused on the heat exchange by natural convection, in single-phase conditions, at atmospheric pressure, between a cylinder, heated by means of the Joule effect, and distilled water, with and without the action of ultrasonic waves. The variables involved in the heat exchange have been varied within the range allowed by the experimental apparatus and the convective heat transfer coefficient has been maximized. The specific thermal flow has been chosen in a range compatible with applications in the field of electronics. For the first time the pressure of water at various ultrasonic power levels has been measured, in the vicinity of the cylindrical surface, thanks to the collaboration with the Naval Experimentation and Support Center (CSSN) of the Italian Navy in La Spezia, Italy.

A Theoretical Investigation Into the Optimal Longitudinal Profile of a Horizontal Pin Fin of Least Material Under the Influence of Natural Convection

2005 ◽  
Author(s):  
Chris J. Kobus
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Maximum Heat ◽  
Pin Fin ◽  
Special Cases

Fundamental level research is presented in this paper discovering the optimum pin fin profile maximizing material utilization (maximum heat transfer with minimum volume) in the case of natural convection. Although this problem has been studied in the past, the current research allows for an axially variable convective heat transfer coefficient due to the axially variable diameter in such pin fins. The current model is compared with previous studies assuming a constant convective heat transfer coefficient. The comparison shows the prior solutions to be special cases of the model in the current research.

Experimental study on natural convection greenhouse drying of papad

2013 ◽  
Vol 24 (4) ◽  
pp. 37-43 ◽  
Author(s):  
Mahesh Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Linear Regression Analysis ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Value

In this paper, the convective heat transfer coefficients of papad for greenhouse drying under a natural convection mode are reported. Various experiments were conducted during the month of April 2010 at Guru Jambheshwar University of Science and Technology Hisar, India (29o5’5” N 75o45’55” E). Experimental data obtained for the natural convection greenhouse drying of papad was used to evaluate the constants in the Nusselt number expression by using simple linear regression analysis. These values of the constant were used further to determine the values of the convective heat transfer coefficient. The average value of a convective heat transfer coefficient was determined as 1.23 W/m2 oC. The experimental error in terms of percent uncertainty was also evaluated.

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