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Monday, August 3, 2020 | History

2 edition of Measuring thermal contact resistance under an impacting droplet of molten metal. found in the catalog.

Measuring thermal contact resistance under an impacting droplet of molten metal.

Yoav Heichal

Measuring thermal contact resistance under an impacting droplet of molten metal.

by Yoav Heichal

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About the Edition

An experimental investigation was performed on the thermal contact resistance values between molten metal droplets and metal substrates. Droplet impact was photographed and substrate surface temperature variation under the impacting droplet was measured using ultra fast temperature sensors that were developed especially for the purposes of this research. The thermal contact resistance during the first few milliseconds of impact was obtained by matching measured surface temperature variation with an analytical solution of the 1-D transient conduction equation. The process was repeated for different surface roughness, different impact velocity and different surface contaminations. An analytical model was developed in order to predict the contact resistance values by estimating the true area of contact between liquid metal and a rough solid. The test results agreed well with the analytical model predictions. Thermal contact resistance increased moderately with an increase in surface roughness, decrease in contact pressure and the presence of surface contaminations.

The Physical Object
Pagination109 leaves.
Number of Pages109
ID Numbers
Open LibraryOL20239030M
ISBN 100494025220

  The thermal (phonon) conductivity of glass has been measured by contacting the sample with a metal at a different uniform initial temperature. The subsequent temperature response in the metal is measured by a tiny thermocouple just underneath the (contact) surface. The coefficient of heat penetration λρc p follows directly from the fitted asymptotic temperature jump or drop for long by: temperature is proportional to the value of thermal contact resistance which acts at the interface. It can be formulated as [2] qA T Q T R c ' ' (4) The reciprocal of thermal contact resistance is termed as thermal contact c o ndu ctance. Figure shows the temperature profile at an interface. The heat transfer across the.

DETERMINATION OF THERMAL CONTACT RESISTANCE BETWEEN METALS USING A PULSE TECHNIQUE. by. WILLIAM EDWARD STEWART, JR. A DISSERTATION Presented to 'be Faculty. o~ the Graduate School. o~ the UNIVERSITY OP MISSOURI-ROLLA In Partial FUlfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY. in. MECHANICAL ENGINEERING. . A parametric study is conducted to examine the effects of droplet size, impact velocity, superheating of droplets, substrate temperature, thermal contact resistance, and wetting angle on spreading of the splat and its flattening by:

temperature measurement of molten metal is a relatively rough method that cannot guarantee the high accuracy mostly required. Moreover, this method only measures the temperature at the metal surface. Thermoelectric temperature measurements with noble metal thermocouples dipped in the molten metal bath actually provide the best solution. Nowadays. However, the thermal contact resistance varies with both time and position. Xue et al incorporated the variable interfacial thermal contact resistance instead of a constant into their numerical model to predict a molten metal droplet impact and solidification on a rough solid surface. Besides the droplet impingements on the horizontal surface.


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Measuring thermal contact resistance under an impacting droplet of molten metal by Yoav Heichal Download PDF EPUB FB2

Thermal contact resistance between molten metal droplets (aluminum alloy and bismuth) and solid plates (steel and brass) was measured experimentally. The diameter of the droplets was 4 mm ⁠, and droplet impact velocity ranged between 1 and 3 m ∕ s ⁠.Cited by: Thermal contact resistance between a surface and an impinging molten droplet has been estimated by either measuring the substrate temperature variation, or the cooling rate of a molten drop after it spread on a metallic substrate.

However, in all these investigations the response time of the temperature sensors was much longer than the time taken for a droplet to spread during impact, so that their measurements are not applicable to the instant of initial impact Cited by: Thermal contact resistance values have been measured directly under millimeter sized droplets of molten metal impacting on flat surfaces by measuring either the splat surface temperature variation using an optical pyrometer [2], [10], [11], or the transient substrate temperature with thermocouples [8], [12].Cited by: Additonally, contact resistance between a drop and the surface has been studied in the context of molten metal droplet impingement and solidification with values ranging between 10 −4 to 10 −6.

The effect of thermal contact resistance (TCR) on the droplet spreading and solidification was investigated using different values of TCR and different droplet sizes. The solidification time was found to be a linear function of the droplet diameter square.

Viscous dissipation, wettability and surface tension effects are taken into by: 1. C is the thermal contact resistance between droplet and substrate per unit area, T and T W are the local temperatures of droplet and substrate, respectively.

Val-ues of R. The spreading and simultaneous solidification of a liquid droplet upon its impingement onto a substrate permitting thermal contact resistance has been numerically simulated; the effect of contact.

Thermal contact resistance at the droplet-substrate interface is also included in the model. Specific attention is paid to the simulation of droplet impact under plasma spraying conditions. Droplet sizes ranged from 15 to 60 microns with initial velocities of m/ by: measure the temperature under impacting molten tin droplets on a stainless steel substrate.

They estimated the value of the thermal contact resistance by matching the transient measured surface temperature with an analytical solution [26]. Wang and QiuAuthor: Rajneesh Bhardwaj, Jon P. Longtin, Daniel Attinger. Abstract: The thermal contact resistance between the balls and the inner and outer rings of an angular contact ball bearing is investigated.

It is assumed that the bearing sustains thrust, radial, or combined loads under aFile Size: 1MB. the bulk thermal conductivity and contact resistance values. Four of the five materials tested had conductivity values of less than 1 W/mK, and the data demonstrates that a small but significant thermal contact resistance exists between the adhesive and the substrate for each of the adhesives.

NOMENCLATURE A area m2 BLT bondline thickness mm k. A fundamental understanding of the fluid flow and heat transfer that occurs during the spreading and solidification of a molten droplet on a substrate is crucial because of its potential applications in many industrial areas.

In this research, thermal contact heat transfer in a rapid contact. Thermal contact resistance values have been measured directly under millimeter sized droplets of molten metal impacting on flat surfaces by measuring either the splat surface temperature variation.

Experiments were done to determine conditions under which vertical columns could be built by metal droplets landing sequentially on top of each other. Molten tin droplets (⁠ mm diameter) were deposited using a pneumatic droplet generator on an aluminum by: We photographed impact of molten zinc and tin droplets on a flat steel surface from which the tip of a small pin was projecting.

The height of the pin and its distance from the droplet center was varied. sistance, we have proposed a new experimental approach for measurement of the thermal contact resistance. Taking the thermal contact resistance between phe-nolic resin and carbon-carbon composites, cuprum, and aluminum as the exam-ples, the influence of the thermal contact resistance between specimens under pressure is tested by experiment.

parameters. Using this approach, several temperature measure-ments under relatively large ~mm size. solidifying droplets have been performed and matched with numerical simulations in order to estimate the values of the thermal contact resistance between the splat and the substrate [email protected]–10#.

or to estimate the nucleation temperature [email protected]#!. Droplets of molten aluminium, 4 mm in diameter, were formed using a pneumatic droplet generator and allowed to fall under their own weight onto a H tool steel plate from a height of m so that the impact velocity was approximately 3 m/ by: The resulting change in the contact resistance due to the different TIMs alters the total thermal resistance (often referred to as junction-to-heat-sink or junction-to-ambient thermal resistance) under steady-state conditions and therefore for a single device, the thermal impedance curves from the two.

A measuring method for the kinetic coefficient and activation energy of molten metals has been developed. This method is based on a splat thickness measurement of a molten metal droplet deposited on a polished metal by: 6.

Measurement and Prediction of Thermal Contact Resistance Across Coated Joints* Christine T. Merrill and Suresh V. Garimella† Cooling Technologies Research Center, School of Mechanical Engineering Purdue University, West Lafayette, Indiana USA ABSTRACT.Determining thermal contact conductance in bolted joints is a major challenge when designing for space application.

The lack of heat transfer through convection enforces the need for full understanding of thermal contact conductance, and the in uencing physical parameters. Due to the uncertain variance of pressure distribution in a bolted.For molten lead droplets, imperfect thermal contact was experimentally observed by Bennett and Poulikakos [11].

Pasandideh-Fard et al. [18] and Xiong et al. [19] performed a numerical study on the sensitivity to contact resistance on the final diameter, overall shape and height of a solidified solder droplet.