Dynamic and Controlled Tuning of the Boiling Curve During Quenching

2016 ◽  
Author(s):  
Arjang Shahriari ◽  
Mark Hermes ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Cooling Rate ◽  
Electric Fields ◽  
Vapor Layer ◽  
Steam Generation ◽  
Transfer Enhancement ◽  
Heat Transfer Mode ◽  
Electrical Control ◽  
Transfer Mode ◽  
Quenching Media

Boiling influences many industrial processes like quenching, desalination and steam generation. Boiling heat transfer at high temperatures is limited by the formation of a vapor layer between the solid and fluid. Low thermal conductivity of this vapor layer inhibits heat transfer. Electrowetting (EW) fields can breakdown this vapor layer to promote wetting, and this concept works for many quenching media including water and organic solvents. This work studies the suppression of this vapor layer and measures the resulting heat transfer enhancement during quenching of metals. We image the fluid-surface interactions and boiling patterns in the presence of an electrical voltage. EW fields replace film boiling with periodic wetting-rewetting cycles and thus fundamentally change the heat transfer mode. The increased wettability substantially reduces the cool down time. The cooling rate can by increased by as much as 3X. The results show that electric fields can dynamically tune the classical quenching curve. This study opens up new avenues to control the metallurgy of metals via electrical control of the cooling rate.

Electrical Suppression of Film Boiling During Quenching

2016 ◽  
Author(s):  
Arjang Shahriari ◽  
Mark Hermes ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Cooling Curve ◽  
Vapor Layer ◽  
Steam Generation ◽  
Voltage Dependent ◽  
Order Of Magnitude ◽  
Leidenfrost Effect ◽  
Solid Liquid Interface

Boiling heat transfer impacts the performance of various industrial processes like quenching, desalination and steam generation. At high temperatures, boiling heat transfer is limited by the formation of a vapor layer at the solid-liquid interface (Leidenfrost effect), where the low thermal conductivity of the vapor layer inhibits heat transfer. Interfacial electrowetting (EW) fields can disrupt this vapor layer to promote liquid-surface wetting. This concept works for a variety of quenching media including water and organic solvents. We experimentally analyze EW-induced disruption of the vapor layer, and measure the resulting enhanced cooling during quenching. Imaging is employed to visualize the fluid-surface interactions and understand boiling patterns in the presence of an electrical voltage. It is seen that EW fundamentally changes the boiling pattern, wherein, a stable vapor layer is replaced by intermittent wetting of the surface. This switch in the heat transfer mode substantially reduces the cool down time. An order of magnitude increase in the cooling rate is observed. An analytical model is developed to extract instantaneous voltage dependent heat transfer rates from the cooling curve. The results show that electric fields can alter and tune the traditional cooling curve. Overall, this study presents a new concept to control the mechanical properties and metallurgy, by electrical control of the quench rate.

Single-Phase Heat Transfer Enhancement Techniques in Microchannel and Minichannel Flows

2004 ◽  
Author(s):  
Mark E. Steinke ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Electric Fields ◽  
Single Phase ◽  
Flow Boiling ◽  
Swirl Flow ◽  
Flow Transition ◽  
Transfer Enhancement ◽  
Compact Heat Exchangers ◽  
Chip Cooling

The single-phase heat transfer enhancement techniques are well established for conventional channels and compact heat exchangers. The major techniques include flow transition, breakup of boundary layer, entrance region, vibration, electric fields, swirl flow, secondary flow and mixers. In the present paper, the applicability of these techniques for single-phase flows in microchannels and minichannels is evaluated. The microchannel and minichannel single-phase heat transfer enhancement devices will extend the applicability of single-phase cooling for critical applications, such as chip cooling, before more aggressive cooling techniques, such as flow boiling, are considered.

Research and Numerical Simulation of Heat Transfer Problems in the Industrial Production

2013 ◽  
Vol 756-759 ◽  
pp. 1679-1683
Author(s):  
Dong Mei Li ◽  
Xin Chun Wang ◽  
Li Nan Shi ◽  
Bo Chao Qu
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Steel Industry ◽  
Heat Transfer Mode ◽  
Radiation Model ◽  
Transfer Mode ◽  
The Difference ◽  
Transfer Problems ◽  
Direct Problems ◽  
The Impact

This article focuses on heat conduction problems in the process of steel industry. Modeling the direct problems of heat transfer, establish heat conduction and thermal radiation model. Model discretization method are used, discussion process from one dimension to two. We give the difference schemes, and the numerical example. Through the results we compare differences between one and two dimensional models, and the impact to the results of the two heat transfer mode.

The Influence of External Electric Field on Heat Transfer at Boiling on Non-Uniform Surfaces

2010 ◽  
Author(s):  
Alexey A. Eronin ◽  
Stanislav P. Malyshenko ◽  
Anton I. Zhuravlev
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Electric Fields ◽  
Heated Surface ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Major Mechanism ◽  
External Electric Fields ◽  
Different Types ◽  
Field Traps

Characteristics of heat transfer and hydrodynamics of boiling of liquid nitrogen on the surfaces with different types of non-uniformities at the presence of external electric fields are experimentally investigated. It is shown that the formation of field traps is a major mechanism of heat transfer enhancement. And this effect result in noticeable change of two-phase hydrodynamics in vicinity of heated surface.

scholarly journals Thermophysical Characterization and Numerical Investigation of Three Paraffin Waxes as Latent Heat Storage Materials

2019 ◽  
Author(s):  
Manel Kraiem ◽  
Mustapha Karkri ◽  
Sassi Ben Nasrallah ◽  
patrick sobolciak ◽  
Magali Fois ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Heat Storage ◽  
Numerical Study ◽  
Melting Process ◽  
Heat Transfer Mode ◽  
Transfer Mode ◽  
Paraffin Waxes ◽  
Thermophysical Characterization

Thermophysical characterization of three paraffin waxes (RT27, RT21 and RT35HC) is carried out in this study using DSC, TGA and transient plane source technics. Then, a numerical study of their melting in a rectangular enclosure is examined. The enthalpy-porosity approach is used to formulate this problem in order to understand the heat transfer mechanism during the melting process. The analysis of the solid-liquid interface shape, the temperature field shows that the conduction is the dominant heat transfer mode in the beginning of the melting process. It is followed by a transition regime and the natural convection becomes the dominant heat transfer mode. The effects of the Rayleigh number and the aspect ratio of the enclosure on the melting phenomenon are studied and it is found that the intensity of the natural convection increases as the Rayleigh number is higher and the aspect ratio is smaller. In the second part of the numerical study, a comparison of the performance of paraffins waxes during the melting process is conducted. Results reveals that from a kinetically RT21 is the most performant but in term of heat storage capacity, it was inferred that RT35HC is the most efficient PCM.

Development of a New Heat Transfer Model Near the Quench Front in the Reflooding Phase of a Tight Lattice

2012 ◽  
Author(s):  
Dan Wu ◽  
Hongxing Yu ◽  
Junchong Yu ◽  
Jie Li ◽  
Jiyang Yu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Liquid Film ◽  
Temperature Drop ◽  
Transfer Model ◽  
Heat Transfer Mode ◽  
Transfer Mode ◽  
Film Evaporation ◽  
Quench Temperature ◽  
Tight Lattice

Heat transfer characteristics near the quench front in a reflooding process are quite complex. Large amount of vapor are generated, and the rod clad temperature drops rapidly to near saturation state. Until now, heat transfer mechanism in this region has not been well understood yet. Best estimate codes like RELAP5, COBRA-TF tend to treat the heat transfer mode near the quench front as transition boiling. However, when calculating the reflooding phase of tight lattice, these codes always under-predict the quench temperature, and also the slop of the temperature drop is predicted to be less steep than the experimental data. In this paper, a new heat transfer model near the quench front in the reflooding phase of a tight lattice is developed. Instead of transition boiling, transient liquid film evaporation is considered to be the main heat transfer mode in this region. It is supposed that heat released near the quench front is through liquid film evaporation. Through comparisons with experimental data, it can be concluded that the new model can better predict the quench temperature and the temperature drop slop.

Inverse Analysis of Radiative Heat Transfer Systems

1999 ◽  
Vol 121 (2) ◽  
pp. 481-484 ◽  
Author(s):  
M. R. Jones
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Inverse Analysis ◽  
Radiative Heat ◽  
Inverse Methods ◽  
Heat Transfer Mode ◽  
Inverse Approach ◽  
Transfer Mode ◽  
Industrial Problem

The design of heat transfer systems in which radiation is the dominant heat transfer mode is an important industrial problem. Compared to the conventional forward approach, the inverse approach allows a more thorough analysis of a potential design. This note demonstrates that inverse methods can be powerful tools in the analysis of radiative heat transfer systems.

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