• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.304-310
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• 2015

Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously, which promoted the heat transfer process at the same working condition.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.90-99
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• 1984

A onetimensional distribution of the temperature and the heat source in the SOI (silicon-on-insulator) multi-layer structure illuminated by tungsten lamps from both sides was obtained by solving the heat equation in steady state on a finite difference grid using successive over-relaxation method. The heat source distribution was obtained by considering such features as spectral components of the light source, multiple reflection at the internal interfaces, temperature and frequency dependence of the light absorption coefficient, etc. The front and back surface temperatures, which are boundary conditions for the heat equation, were derived from a requirement that they satisfy the radiation conditions. The radiation flux as well as the conduction flux was considered in modelling the thermal behaviour at the internal interfaces. Since the temperature and the heat source profiles are strongly dependent upon each other, the calculation of each profile was iterated using the updated profile of the other until they are consistent with each other. The experimental temperature at the front surface of the wafer as measured by Pyrometer was about 1200$^{\circ}$K, while the simulated temperature was 1120$^{\circ}$K.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.383-386
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• 2006

Subsurface temperature is affected by heat advection due to groundwater advection. Temperature-depth profile can be perturbed especially when there are significant vertical groundwater flux caused by external force such as injection or extraction. This research is to clarify the change of subsurface temperature distribution when the 40m x l0m sandy aquifer is stimulated by two different vertical flux($case1:\;{\pm}10^{-5}m^3/s,\;case2:\;{\pm}4{\times}10^{-5}m^3/s$) using a program called HydroGeoSphere. The resulting temperature distribution contour map shows pumping causes vertical attraction of water from deeper and warmer place which result in rising up isotherm. Additionally more injection/extraction rate, more vertical groundwater flux leads to faster Increase in temperature near the pumping well.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.39-45
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• 2001

With uniform heat generation from the inner surface of the cylindrical heater placed in a cross flow boundary condition, heat flow that is conducted along the wall of the heater creates a non-isothermal surface temperature and non-uniform heat flux distribution. In the present investigation, the effects of circumferential wall heat conduction on convection heat transfer is investigated for the case of forced convection around horizontal circular tube in cross flow of air. The wall conduction number which can be deduced from the governing energy equation should be used to express the effect of circumferential wall heat conduction. It is demonstrated that the circumferential wall heat conduction influences local Nusselt numbers of one-dimensional and two-dimensional solutions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.523-534
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• 1998

The convection heat transfer on horizontal circular tube is studied as a conjugated heat transfer problem. With uniform heat generation in a cylindrical heater placed in a cross flow boundary condition, heat flow that is conducted along the wall of the heater creates a non-isothermal surface temperature and non-uniform heat flux distribution. In the present investigation, the effects of circumferential wall heat conduction on convection heat transfer are investigated for the case of forced convection around horizontal circular tube in cross flow of air and water. Non-dimensional conjugation parameter $ K^*$ which can be deduced from the governing energy differential equation should be used to express the effect of circumferential wall heat conduction. Two-dimensional temperature distribution$ T({\gamma,\theta})$ is presented. The influence of circumferential wall heat conduction is demonstrated on graph of local Nusselt number.

• Nuclear Engineering and Technology
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• v.37 no.5
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• pp.457-468
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• 2005

An experimental study on post-CHF heat transfer has been performed with a $3\times3$ rod bundle using a vertical steam-water two-phase flow at low flow conditions. The effects of various parameters on the post-CHF heat transfer are investigated and the reasons for the parametric effects are discussed. As the heat transfer regime changes from CHF to post-CHF, the radial wall temperature distribution is changed depending on the pressure and the mass flux conditions. The superheat of the fluid increases considerably with an increase of the wall temperature (or heat flux) and with a decrease of the mass flux. This implies, indirectly, a strong thermal non-equilibrium at high wall temperature and low mass flux conditions. In order to improve the prediction accuracy of the existing post-CHF correlations, it is necessary to perform more experiments, particularly direct measurement of the vapor superheat, and to modify the correlation by considering a strong thermal non-equilibrium at low flow and low pressure conditions.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.259-264
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• 2009

Most of the fossil power plants firing lower grade coals are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. The poor combustion conditions are directly related to the gas flow deviation in upper furnace and convection tube-bank but a less reported issue related to in large-scale oppose wall fired boilers. In order to develop a on-line combustion monitoring system and suggest an alternative heat flux estimation method at tube bank, which is very useful information for boiler design tool and blower optimizing system, field test was conducted at operating power boiler. During the field test the exhaust gases' temperature and tube metal temperature were monitored by using a spatially distributed sensors grid which located in the boiler's high temperature vestibule region. At these locations. the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. Test results showed that the flue gas monitoring method is more proper than metal temperature distribution monitoring for real time combustion monitoring because tube metal temp. distribution monitoring method is related to so many variables such as flue gas, internal flow unbalance, spray etc., Heat flux estimation at the tube bank with flue gas temp. and metal temp. data can be alternative method when tube drilling type sensor can't able to use.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.381-386
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• 2000

The brake force of drum brakes for commercial vehicles is applied by a s-cam. First of all the influence of the s-cam load angles and elastic modulus of the pad on the contact pressure distribution between pad and drum was checked by using 3 dimensional finite element model. In the second part, temperature and thermal stress analyses were carried out by an axisymmetric model with constant heat flux and pressure-proportional heat flux. In the case of temperature analysis the heat conduction from the interface to the pad and the drum was modeled using a thin soft film element, so artificial division of the generated heat flux between pad and drum is not necessary. The analysis was performed by ABAQUS/Standard code.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.79-85
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• 2005

This work is to investigate the surface heat flux and combustion characteristics of premixed propane mixture in a constant volume chamber. The experiment of heat flux and combustion characteristics of premixed propane mixture are performed with various equivalence ratio and initial pressure conditions. Based on the experimental results, it is found that the maximum instantaneous temperature is increased with the increase of initial pressure in the chamber. There are significant differences in the burning velocity of premixed propane mixture at different measuring points in the constant volume combustion chamber. A]so, the trends of temperature difference at each measuring points are similar to the burning velocity in the combustion chamber. It is concluded that the total heat loss during the combustion period is affected by the equivalence ratio and the initial condition of fuel-air mixture.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.129-136
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• 2017

Effects of collision angle on heat transfer characteristics of a liquid droplet impinging on a heated wall above the Leidenfrost point temperature were experimentally investigated. The heated wall and droplet temperatures were $506^{\circ}C$ and $100^{\circ}C$, respectively, and the impact angle varied from $20^{\circ}$ to $90^{\circ}$ while the normal collision velocity was constant at 0.27 m/s. The droplet collision behaviors and the surface temperature distribution were measured using synchronized high-speed video and infrared cameras. The major physical parameters influencing upon droplet-wall collision heat transfer, such as residence time, wall heat flux, effective heat transfer area, heat transfer amount, were analyzed. It was found at the constant normal collision velocity that the residence time, wall heat flux and effective heat transfer area were hardly not changed, resulting in the almost constant heat transfer amount.