On inverse boundary heat-conduction problems for recovery of heat fluxes to anisotropic bodies with nonlinear heat-transfer characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

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Numerical Investigation of Heat Transfer Characteristics of Debris Bed After Severe Accident of SFR Based on 1-D Heat Conduction Model

Volume 6A: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-81296 ◽

2018 ◽

Author(s):

Mengwei Zhang ◽

Bin Zhang ◽

Jianqiang Shan

Keyword(s):

Heat Transfer ◽

Heat Conduction ◽

Transfer Process ◽

Severe Accident ◽

Heat Transfer Characteristics ◽

Conduction Model ◽

One Dimensional ◽

The Core ◽

Transfer Characteristics ◽

Core Catcher

Nuclear reactor severe accidents can lead to the release of a large amount of radioactive material and cause immense disaster to the environment. Since the Fukushima nuclear accident in Japan, the severe accident research has drawn worldwide attention. Based on the one-dimensional heat conduction model, a DEBRIS-HT program for analyzing the heat transfer characteristics of a debris bed after a severe accident of a sodium-cooled fast reactor was developed. The basic idea of the DEBRIS-HT program is to simplify the complex energy transfer process in the debris bed to a simple one-dimensional heat transfer problem by solving the equivalent thermal conductivity in different situations. In this paper, the DEBRIS-HT program code is prepared by using the existing model and compared with the experimental results. The results show that the DEBRIS-HT program can correctly predict the heat transfer process in the fragment bed. In addition, the heat transfer characteristics analysis program is also used to model the core catcher of the China fast reactor. Firstly, the dryout heat flux when all of molten core dropped on the core catcher was calculated, which was compared with the result of Lipinski’s zero dimensional model, and the error between two values is only 11.2%. Then, the temperature distribution was calculated with the heat power of 15MW.

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Heat Transfer Characteristics of a Train of Droplets Impinging Over a Hot Surface: From Film Evaporation to Leidenfrost Point

Volume 8: Heat Transfer and Thermal Engineering ◽

10.1115/imece2019-11212 ◽

2019 ◽

Author(s):

Ganesh Guggilla ◽

Arvind Pattamatta ◽

Ramesh Narayanaswamy

Keyword(s):

Heat Transfer ◽

High Performance ◽

Heated Surface ◽

Electronics Cooling ◽

Spray Cooling ◽

High Heat ◽

Heat Fluxes ◽

Air Cooling ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

Abstract Due to the advancements in computing services such as machine learning and artificial intelligence, high-performance computing systems are needed. Consequently, the increase in electron chip density results in high heat fluxes and required sufficient thermal management to maintain the servers. In recent times, the liquid cooling techniques become prominent over air cooling as it has significant advantages. Spray cooling is one such efficient cooling process which can be implemented in electronics cooling. To enhance the knowledge of the process, detailed studies of fundamental mechanisms involved in spray cooling such as single droplet and multiple droplet interactions are required. The present work focuses on the study of a train of droplets impinging over a heated surface using FC-72 liquid. The surface temperature is chosen as a parameter, and the Dynamic Leidenfrost point (DLP) for the present impact conditions is identified. Spread hydrodynamics and heat transfer characteristics of these consecutively impinging droplets till the Leidenfrost temperature, are studied and compared.

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Heat Transfer Characteristics of Subcooled Water Flow Boiling in Circular Channels With Non-Uniform Heating Fluxes

ASME 2016 Power Conference ◽

10.1115/power2016-59475 ◽

2016 ◽

Author(s):

Ge Zhu ◽

Qincheng Bi ◽

Jianguo Yan ◽

Qizheng Yuan ◽

Haicai Lv ◽

...

Keyword(s):

Heat Transfer ◽

Mass Flow ◽

High Heat ◽

Heat Fluxes ◽

Dominant Factor ◽

Uniform Heating ◽

Heat Transfer Characteristics ◽

Subcooled Water ◽

Transfer Characteristics ◽

Twisted Tapes

Experiments of heat transfer characteristics of subcooled water flowing in vertical circular channels, which were off-center in rectangular blocks, were carried out under high heat fluxes up to the ITER requirements. The heating flux distributions of the channels were non-uniform in the circumferential direction, which were obtained by electrically heating the blocks directly. Two types of channels were used: smooth channel and twisted tapes channel. The surface temperature of the rectangular blocks was measured by infrared camera and thermocouples. Effect of the system pressure, mass flow rate, inlet subcooling, and equivalent heat fluxes on heat transfer were all investigated. The main attention was paid to the subcooled water heat transfer under non-uniform heating flux, and the effect of twisted tapes. Results show that subcooled boiling is more likely to become the dominant factor under the conditions of lower mass flow rates, higher heat fluxes and lower system pressures. Twisted tapes can enhance the heat transfer, which is more evident in high heat fluxes. The temperature fields in the block were calculated with a Computational Fluid Dynamics (CFD) method to obtain, which were consistent with the experimental results.

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Laboratory Experimental Setup and Research on Heat Transfer Characteristics during Secondary Cooling in Continuous Casting

Metals ◽

10.3390/met9010061 ◽

2019 ◽

Vol 9 (1) ◽

pp. 61 ◽

Cited By ~ 3

Author(s):

Yazhu Zhang ◽

Zhi Wen ◽

Zengwu Zhao ◽

Chunbao Bi ◽

Yaxiang Guo ◽

...

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Continuous Casting ◽

Water Flux ◽

Spray Cooling ◽

Heat Fluxes ◽

Secondary Cooling ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Surface Temperatures

Spray cooling is a key technology in the continuous casting process and has a marked influence on the product quality. In order to obtain the heat transfer characteristics, which are closer to the actual continuous casting to serve the design, prediction and simulation, we created an experimental laboratory setup to investigate heat transfer characteristics of air mist spray cooling during the continuous casting secondary cooling process. A 200-mm thick sample of carbon steel was heated above 1000 °C, and then cooled in a water flux range of 0.84 to 3.0 L/(m2∙s). Determination of the boundary conditions involved experimental work comprising an evaluation of the thermal history and the heat flux and heat transfer coefficient (HTC) at the casting surface using inverse heat conduction numerical schemes. The results show that the heat fluxes were characterized via boiling curves that were functions of the slab surface temperatures. The heat flux was determined to be 2.9 × 105 W/m2 in the range of 1100 to 800 °C with a water flux of 2.1 L/(m2∙s). The critical heat flux increased with the increase of water flux. The HTC was close to a linear function of water flux. We also obtained the relation between the HTC and the water flux in the transition boiling region for surface temperatures of 850 to 950 °C.

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Heat Transfer Behaviour of Nano Fluid at High Pressure

Journal of Materials Science and Surface Engineering ◽

10.52687/2348-8956/111 ◽

2013 ◽

Vol 1 (1) ◽

pp. 1-3

Author(s):

O.S. Prajapati ◽

◽

N. Rohatgi ◽

A.K. Rajvanshi ◽

◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Heat Fluxes ◽

Heat Transfer Characteristics ◽

Particle Volume ◽

Variable Effect ◽

Transfer Characteristics ◽

Nano Fluid ◽

Study Heat Transfer

Recent investigations on nanofluids indicate that the suspended nanoparticles markedly change the heat transfer characteristics of the suspension. In this study, heat transfer characteristics of ZnO-water nanofluids were investigated. Experiments were conducted with ZnO-water nanofluids at particle volume concentrations up to 0.1 volume %, constant subcooling of 20°C, pressure 2 bar, mass flux 400 kg/m2 s and heat fluxes up to 500 kW/m2 with variable. Effect of heat flux and nanofluid concentration on heat transfer coefficient of ZnO-water nanofluids was investigated. Study reveals that heat transfer coefficient increases with ZnO-water nanofluids.

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Heat transfer characteristics of subcooled water in a hypervapotron under high mass fluxes and high heat fluxes

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2018.09.102 ◽

2019 ◽

Vol 129 ◽

pp. 580-590 ◽

Cited By ~ 2

Author(s):

Ge Zhu ◽

Qincheng Bi ◽

Jianguo Yan ◽

Teng Wang ◽

Jinle Zhao

Keyword(s):

Heat Transfer ◽

High Heat ◽

Heat Fluxes ◽

High Mass ◽

Heat Transfer Characteristics ◽

Subcooled Water ◽

Transfer Characteristics ◽

Mass Fluxes

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AZ31-alloy, H13-die combination heat transfer characteristics by using inverse heat conduction algorithm

Materials Today Proceedings ◽

10.1016/j.matpr.2020.11.258 ◽

2020 ◽

Author(s):

Vivek Pandey ◽

Nand Jee Kanu ◽

Gyanendra Kumar Singh ◽

Bekele Gadissa

Keyword(s):

Heat Transfer ◽

Heat Conduction ◽

Az31 Alloy ◽

Inverse Heat Conduction ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

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Heat Transfer Characteristics of a Train of Droplets Impinging Over a Hot Surface: From Film Evaporation to Leidenfrost Point

Journal of Heat Transfer ◽

10.1115/1.4050718 ◽

2021 ◽

Author(s):

Ganesh Guggilla ◽

Ramesh Narayanaswamy ◽

Peter Stephan ◽

Arvind Pattamatta

Keyword(s):

Heat Transfer ◽

High Speed ◽

Heated Surface ◽

Contact Angle Hysteresis ◽

Electronics Cooling ◽

Spray Cooling ◽

Heat Fluxes ◽

High Speed Photography ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

Abstract High-performance computing systems are needed in advanced computing services such as machine learning and artificial intelligence. Consequently, the increase in electron chip density results in high heat fluxes and requires good thermal management to maintain the servers. Spray cooling using liquid offers higher heat transfer rates and is efficient when implemented in electronics cooling. Detailed studies of fundamental mechanisms involved in spray cooling, such as single droplet and multiple droplet interactions, are required to enhance the process's knowledge. The present work focuses on studying a train of two FC-72 droplets impinging over a heated surface. Experimental investigation using high-speed photography and infrared thermography is conducted. Simultaneously, numerical simulations using opensource CFD package, OpenFOAM are carried out, emphasizing the significance of contact angle hysteresis. The surface temperature is chosen as a parameter, and different boiling regimes along with Dynamic Leidenfrost point (DLP) for the present impact conditions are identified. Spreading hydrodynamics and heat transfer characteristics of these consecutively impinging droplets till the Leidenfrost temperature, are studied and compared.

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