Investigation of heat transfer from circular cylinders in high power 10 kHz and 20 kHz acoustic resonant fields

A novel experimental method was developed to measure the rapid transient temperature variations (heating rate > 107 K/s) of porous samples heated by high surface heat fluxes. With a thin film (0.1 μm thick) resistance thermometer of platinum as the temperature sensor and a super-high speed digital oscilloscope (up to 100 MHz) as the data recorder, rapid transient temperature variation in a porous material heated by a microsecond laser pulse of high power density is measured. Experimental results indicate that for high heat transfer cases (q′ > 109 W/m2) with short durations (5 – 20 μs) of heating, non-Fourier heat conduction behaviors appear. The non-Fourier hyperbolic heat conduction model and the traditional Fourier parabolic model are employed to simulate this thermal case respectively and the FDM is used to perform the numerical analysis. The hyperbolic model predicts thermal wave behavior in qualitative agreement with the experimental data.

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Phase-change immersion cooling high power light emitting diodes and heat transfer improvement

Microelectronics Reliability ◽

10.1016/j.microrel.2017.05.033 ◽

2017 ◽

Vol 79 ◽

pp. 257-264 ◽

Cited By ~ 6

Author(s):

Xue Kang ◽

Yiping Wang ◽

Qunwu Huang ◽

Yong Cui ◽

Chen Wang ◽

...

Keyword(s):

Heat Transfer ◽

Phase Change ◽

High Power ◽

Light Emitting Diodes ◽

Light Emitting ◽

Immersion Cooling ◽

Heat Transfer Improvement

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Unsteady Boundary Layers on a Flat Plate Disturbed by Periodic Wakes: Part I — Measurement of Wake-Affected Heat Transfer and Wake-Induced Transition Model

Volume 1: Turbomachinery ◽

10.1115/94-gt-429 ◽

1994 ◽

Author(s):

K. Funazaki

Keyword(s):

Heat Transfer ◽

Flat Plate ◽

Rotating Disk ◽

Circular Cylinders ◽

Transition Model ◽

Time Diagram ◽

Test Conditions ◽

Intermittency Factor ◽

Unsteady Boundary Layers ◽

Good Agreement

Measurements of wake-affected heat transfer distributions on a flat plate are made by use of a wake generator that consists of a rotating disk and several types of circular cylinders. The main purpose of this study is to construct a wake-induced transition model in terms of an intermittency factor, considering the evolution of the wake-induced turbulent region, a so-called turbulent patch in a distance-time diagram. A comparison between the proposed transition model and the measured heat transfer data reveals that the transition model yields good agreement with the measured data of all test conditions in this study.

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Numerical study of forced convection heat transfer over three cylinders in staggered arrangement immersed in porous media

Thermal Science ◽

10.2298/tsci150808249s ◽

2018 ◽

Vol 22 (1 Part B) ◽

pp. 467-475 ◽

Cited By ~ 2

Author(s):

Habib-Olah Sayehvand ◽

Sakene Yari ◽

Parsa Basiri

Keyword(s):

Heat Transfer ◽

Porous Media ◽

Forced Convection ◽

Numerical Study ◽

Convection Heat Transfer ◽

Circular Cylinders ◽

Convection Heat ◽

State Equations ◽

Forced Convection Heat Transfer ◽

Staggered Arrangement

Staggered arrangement is one of the common configurations in heat exchangers that make better mixing of flow and heat transfer augmentation than other arrangements. In this paper forced convection heat transfer over three isothermal circular cylinders in staggered configuration in isotropic packed bed was investigated. In this work laminar 2-D incompressible steady-state equations of momentum and energy were solved numerically by finite volume method. Simulation was done in three Reynolds numbers of 80, 120, and 200. The results indicate that, using porous medium the Nusselt number enhanced considerably for any of cylinders and it presents thin temperature contours for them. Also is shown that by increasing Reynolds number, the heat transfer increased in both channel but the growth rate of it in porous media is larger. In addition, results of simulation in porous channel show that with increasing Peclet number, heat transfer increased logarithmically.

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UPWARD FLOW AND HEAT TRANSFER AROUND TWO HEATED CIRCULAR CYLINDERS IN SQUARE DUCT UNDER AIDING THERMAL BUOYANCY

Journal of the Serbian Society for Computational Mechanics ◽

10.24874/jsscm.2020.14.01.10 ◽

2020 ◽

Vol 14 (1) ◽

pp. 113-123

Author(s):

H. Laidoudi

Keyword(s):

Heat Transfer ◽

Convection Heat Transfer ◽

Circular Cylinders ◽

Upward Flow ◽

Square Duct ◽

Thermal Buoyancy ◽

Flow And Heat Transfer ◽

Ansys Cfx ◽

Commercial Code ◽

Physical Phenomena

This paper presents a numerical investigation of mixed convection heat transfer around a pair of identical circular cylinders placed in side-by-side arrangement inside a square cavity of single inlet and outlet ports. The investigation provided the analysis of gradual effect of aiding thermal buoyancy on upward flow around cylinders and its effect on heat transfer rate. For that purpose, the governing equations involving continuity, momentum and energy are solved using the commercial code ANSYS-CFX. The distance between cylinders is fixed with half-length of cavity. The simulation is assumed to be in laminar, steady, incompressible flow within range of following conditions: Re = 1 to 40, Ri = 0 to 1 at Pr = 0.71. The main obtained results are shown in the form of streamline and isotherm contours in order to interpret the physical phenomena of flow and heat transfer. The average Nusselt number is also computed and presented. It was found that increase in Reynolds number and/or Richardson number increases the heat transfer. Also, aiding thermal buoyancy creates new form of counter-rotating zones between cylinders.

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Magnetohydrodynamic effects on flow structures and heat transfer over two cylinders wrapped with a porous layer in side

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-03-2015-0112 ◽

2016 ◽

Vol 26 (5) ◽

pp. 1416-1432 ◽

Cited By ~ 8

Author(s):

Saman Rashidi ◽

Javad Abolfazli Esfahani ◽

Mohammad Sadegh Valipour ◽

Masoud Bovand ◽

Ioan Pop

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Flow Field ◽

Porous Layer ◽

Numerical Study ◽

Convection Heat Transfer ◽

Circular Cylinders ◽

Flow Structures ◽

Content Type ◽

The Magnetic Field

Purpose – The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor safety analysis, combustion, compact heat exchangers, solar power collectors, high-performance insulation for buildings and many another applications. The purpose of this paper is to perform a numerical study on flows passing through two circular cylinders in side-by-side arrangement wrapped with a porous layer under the influence of a magnetic field. The authors focus the attention to the effects of magnetic field, Darcy number and pitch ratio on the mechanism of convection heat transfer and flow structures. Design/methodology/approach – The Darcy-Brinkman-Forchheimer model for simulating the flow in porous medium along with the Maxwell equations for providing the coupling between the flow field and the magnetic field have been used. Equations with the relevant boundary conditions are numerically solved using a finite volume approach. In this study, Stuart and Darcy numbers are varied within the range of 0 < N < 3 and 1e-6 < Da < 1e-2, respectively, and Reynolds and Prandtl numbers are equal to Re=100 and Pr=0.71, respectively. Findings – The results show that the drag coefficient decreases for N < 0.6 and increases for N > 0.6. Also, the effect of magnetic field is negligible in the gap between two cylinders because the magnetic field for two cylinders counteracts each other in these regions. Originality/value – To the authors knowledge, in the open literature, flow passing over two circular cylinders in side-by-side arrangement wrapped with a porous layer has been rarely investigated especially under the influence of a magnetic field.

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Состояние разработок двухфазных систем терморегулирования космических аппаратов

Aerospace technic and technology ◽

10.32620/aktt.2021.2.05 ◽

2021 ◽

pp. 36-51

Author(s):

Рустем Юсуфович Турна ◽

Артем Михайлович Годунов

Keyword(s):

Heat Transfer ◽

Control System ◽

Power Consumption ◽

High Power ◽

Single Phase ◽

Thermal Control ◽

Two Phase ◽

Thermal Control System ◽

Intensification Of Heat Exchange ◽

Large Heat

The progress of space technology is leading to more and more energy-equipped spacecraft. The International Space Station already has the capacity of solar panels of more than 100 kW. Autonomous spacecrafts and satellites (including stationary ones) have the capacity of power units of kW, in the nearest future - more than 10 kW. Forced heat transfer using single-phase liquid coolants is still considered as the main method of thermal control on high-power spacecraft (SC). Single-phase mechanically pumped fluid loop is a fully proven means of thermal control of spacecraft with a moderate heat load. A significant disadvantage of such systems is that the coolant temperature varies significantly within the loop. The temperature difference can be reduced by increasing the coolant flow rate, but for this, it is necessary to increase the pump capacity, which inevitably leads to an increase in power consumption, pipeline diameters, and weight of the system as a whole. In the case of spacecraft with high power capacity (more than 5-10 kW) and large heat transfer distances (10 m and more), a two-phase mechanically pumped fluid loop for thermal control is more preferable in terms of weight, the accuracy of thermoregulation, power consumption (and other parameters). The use of a two-phase loop (2PMPL) as a spacecraft thermal control system allows to reduce significantly mass and power consumption for own needs in comparison with a single-phase thermal control system (TCS). The effect is achieved due to the accumulation of transferred heat in the form of latent heat of vaporization and intensification of heat exchange at boiling and condensation of coolant. The article provides a critical review of published works on 2PMPL for spacecraft with high power (more than 5...10 kW) and a large heat transfer distance (more than 10...100 meters) from 1980 up to nowadays. As a result, a list of the main problems on the way of practical implementation of two-phase loops is formed.

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