• 한국유체기계학회 논문집
• /
• 제5권1호
• /
• pp.49-54
• /
• 2002

HANARO, 30 MW of research reactor, was installed at the depth of 13m in an open pool. The $90\%$ of primary coolant was designed to pass through the core and to remove the reaction heat of the cote. The rest, $10\%$, of the primary coolant was designed to bypass the core. And the reactor coolant through and bypass the core was inhaled at the top of chimney by the coolant pump to prevent the radiated gas from being lifted to the top of reactor pool. But, the part of core bypass coolant was not inhaled by the reactor coolant pump and reached at the top of reactor pool by natural convection, and increased the radiation lovel on the top of reactor pool. To reduce the radiation level by protecting the natural convection of the core bypass flow, the hot water layer (HWL, hereinafter) was installed with the depth of 1.2 m from the top of reactor pool. As the HWL was normally operated, the radiation level was reduced to five percent ($5\%$) in comparing with that before the installation of the HWL. When HANARO was operated at a higher temperature than the normal temperature of the HWL by operating the standby heater, it was found that the radiation level was more reduced than that before operation. To verify the reason, the heat loss of the HWL was calculated by Visual Basic Program. It was confirmed through the results that the larger the temperature difference between the HWL and reactor hall was, the more the evaporation loss increased. And it was verified that the radiation level above was reduced mote safely by increasing the capacity of heater.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
• /
• pp.221-226
• /
• 2001

HANARO, 30MW of research reactor, was installed at the depth of 13m of open pool, The $90\%$ of primary coolant was designed to pass through the core and to remove the reaction heat of the core. The rest $10\%$, of the primary coolant was designed to bypass the core. And the reactor coolant through and bypass the core was inhaled at the top of chimney by the coolant pump to protect that the radiated gas was lifted to the top of reactor pool. But, the part of core bypass coolant was not inhaled by the reactor coolant pump and reached at the top of reactor pool by natural convection and increased the radiation level on the top of reactor pool. To reduce the radiation level by protecting the natural convection of the core bypass flow, the hot water layer (HWL, hereinafter) was installed with the depth of 1.2m from the top of reactor pool. As the HWL was normally operated, the radiation level was reduced to five percent ($5\%$) in comparing with that before the installation of the HWL. When HANARO was operated with higher temperature than the normal temperature of the HWL by operating the standby heater, it was found that the radiation level was more reduced than that before operation. To verify the reason, the heat loss of the HWL was calculated. It was confirmed through the results that the larger the temperature difference between the HWL and reactor hall was, the more the evaporation loss was increased. And it was verified that the radiation level above was reduced more safely by increasing the capacity of heater.

• Journal of Welding and Joining
• /
• 제10권4호
• /
• pp.222-229
• /
• 1992

A prediction of penetration and heat affected zone by using Finite Element Method in CO$_{2}$ Arc Welding has been discussed this paper. The temperature distribution of a base metal produced by the CO$_{2}$ arc welding processing is analyzed by using a three dimensional finite element model. The common finite element program ANSYS 4.4A was employed to obtain the numerical results. Temperature dependent material properties, effect of latent heat, and the convective boundary conditions are included in the model. Numerically predicted sizes of the penetration and the heat affected zone are compared with the experimentally observed values. As a result, there was a slight difference between numerical analysis values and experimentally observed values. For in the case of heat affected zone, it was not considered a precise forced convective coefficient value, and in the case of penetration, it was not, considered a arc force.

• 대한기계학회논문집
• /
• 제19권9호
• /
• pp.2353-2364
• /
• 1995

The ignition phenomena of a solid fuel plate of polymethyl-methacrylate(PMMA), which is vertically positioned and exposed to a thermal radiation source, is numerically studied here. A two-dimensional transient model includes such various aspects as thermal decomposition of PMMA, gas phase radiation absorption, gas phase chemical reaction and air entrainment by natural convection. Whereas the previous studies considers the problem approximately in a one-dimensional form by neglecting the natural convection, the present model takes account of the two-dimensional effect of radiation and air entrainment. The inert heating of the solid fuel is also taken into consideration. Radiative heat transfer is incorporated by th Discrete Ordinates Method(DOM) with the absorption coefficient evaluated using gas species concentration. The thermal history of the solid fuel plate shows a good agreement compared with experimental results. Despite of induced natural convective flow that induces heat loss from the fuel surface, the locally absorbed radiant energy, which is converted to the internal energy, is found to play an important role in the onset of gas phase ignition. The ignition is considered to occur when the rate of variation of gas phase reaction rate reaches its maximum value. Once the ignition takes place, the flame propagates downward.

• 설비공학논문집
• /
• 제9권4호
• /
• pp.484-496
• /
• 1997

The fluid flow and heat transfer characteristics of conjugate forced and natural convection in the triple-glazed airflow window, where the outer air passes through a space contrived between the interior and exterior window panes, were studied numerically by a finite volume method for the elliptic form of the Navier-Stokes equations. The investigation focused on the influence of window geometry, ventilastion rate and solar energy on the temperature, velocity distribution and thermal performance of the airflow window. The comparison between the triple-glazed airflow window and the enclosed triple-glazed window was also made to evaluate the effect of buoyancy upon which the thermal performance of the window depended.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.49-53
• /
• 2001

A conventional flame type gas combustion major portion of heat is transferred to the body by convection due to small radiant ability of the gas flame. Increasing the radiation component of heat flux in the combustion zone allows to augment the efficiency of gas utilization. Such effect can be reached by using radiative gas burner applied to metal mesh combustion. Basically the gas radiant burner consists of metallic mesh of high heat resisting steels. In terms of this regards, we have made the burner consisted of metal mesh and measured the radiative flame stability of natural gas/air mixture on the metal mesh burner. The pressure loss through the metal mesh is defined by pressure-velocity slope. The more increased the pressure-velocity slope of the metal mesh is, the wider the stable zone of radiave flame on the metal mesh burner is. And the augmentation of mixture flowrate through the metal mesh make narrow the permissible range of equivalence ratio.

• Journal of applied mathematics & informatics
• /
• 제27권1_2호
• /
• pp.301-313
• /
• 2009

This paper presents a Finite Element Method (FEM) application to thermal study of natural three layers of human dermal parts of varying properties. This paper carries out investigation of temperature distributions in these layers namely epidermis, dermis and under lying tissue layer. It is assumed that the outer skin is exposed to atmosphere and the loss of heat due to convection, radiation and evaporation of water have also been taken into account. The computations are carried out for one dimensional unsteady state case and the shape functions in dermal parts have been considered to be quadratic. A Finite Element scheme that uses the Crank-Nicolson method is used to solve the problem and the results computed have been exhibited graphically.

• 대한기계학회논문집
• /
• 제7권4호
• /
• pp.392-397
• /
• 1983

In the present study, improvement of the solar collector performance by utilizing honeycomb structures is being investigated. Installation of honeycomb structures inside of the collector induces the suppression of would-be natural convection phenomena within the collector enclosure spacing. It also minimizes infrared radiation heat loss from the collector absorber plate to the surrounding. Experiments have been carried out a collector with 40*20mm rectangular honeycombs, 20*20mm square honeycombs and without honeycombs. The results are presented for the three cases for comparisons. The collector model has been installed at various tilt angle from 15.deg. to 60.deg. measured from the ground. The influence of the tilt angle to the heat performance of the collector is also presented.

• 대한기계학회논문집A
• /
• 제27권3호
• /
• pp.393-400
• /
• 2003

Excessive generation of BOG during the LNG transportation not only causes the severe financial loss but also leads to the unexpected disaster. Therefore, the carrier cargo insulating interior LNG should be carefully designed based upon an accurate heat transfer analysis. However. it is not simple to analyze heat transfer of LNG cargo, because it is in a complex insulation structure and LNG carrier experiences a complicated heat transfer according to various kinds of voyage conditions. In this paper, we carried out the transient finite element heat transfer analysis for a cargo of Mark-111 membrane-type LNG carrier during laden voyage, and we compared heat transfer rates between considering natural convection and considering conduction. For this goal, we developed a PCL program incorporating with a commercial MSC/NASTRAN FEM code.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
• /
• pp.812-817
• /
• 1998

Experimental studies on heat transfer and solidification of the molten metal pool with overlying coolant with boiling were performed The simulant molten pool material is tin (Sn) with the melting temperature of 232$^{\circ}C$. Demineralized water and R113 are used as the working coolant. This work examines the crust formation and the heat transfer characteristics of the molten metal pool immersed in the boiling coolant. The Nusselt number and the Rayleigh number in the molten metal Pool region of this study are compared between the water coolant case and the R113 coolant case. The experimental results or the water coolant are higher than those for R113. Also, the empirical relationship of the Nusselt number and the Rayleigh number is compared with the literature correlations measure from mercury. The present experimental results are higher than the literature correlations. It is believed that this discrepancy is caused by the effect of heat loss to the environment on the natural convection heat transfer in the molten pool.