• 한국유체기계학회 논문집
• /
• 제14권5호
• /
• pp.55-62
• /
• 2011

Shape optimization of a Printed circuit heat exchanger (PCHE) has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (3-D RANS) analysis and surrogate modeling techniques. The objective function is defined as a linear combination of effectiveness of the PCHE term and pressure drop in the cold channels of the PCHE. The cold channel angle and the ellipse aspect ratio of the cold channel are used as design variables for the optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results of three types of surrogate model are compared each other. The results of the optimizations indicate improved performance in friction loss but low performance in effectiveness than the reference shape.

• 대한기계학회논문집B
• /
• 제22권4호
• /
• pp.428-439
• /
• 1998

Fluid flow and heat transfer have been numerically investigated for an oscillating flow in a tube with a regenerator. The regenerator is placed between hot and cold spaces which are heated and cooled at uniform temperature. An oscillating flow is generated by the piston motion at both ends of a tube. The time dependent, two-dimensional Navier-Stokes equations and energy equation are solved by using the finite-volume and moving grid method. The regenerator is adopted as Brinkmann-Forchheimer extended Darcy model. Numerical results are obtained for the flow and temperature fields, and described the effects of the oscillating frequency and amplitude ratio by the piston motion as well as the aspect ratio. The numerical results obtained indicate that the heat transfer between the tube wall and oscillating flow is increased as the oscillating frequency, amplitude ratio and the aspect ratio are increased.

• Journal of Mechanical Science and Technology
• /
• 제19권11호
• /
• pp.2053-2060
• /
• 2005

The unsteady Couette flow of an electrically conducting, V1SCOUS, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• 대한기계학회논문집
• /
• 제7권3호
• /
• pp.319-327
• /
• 1983

The thermal diffusivity one of the series of standard pieces for spark test are determined by the flash method. The standard pieces are composed with carbon steels, structural carbon steels, alloy steels and high speed tool steels. In order to compute the thermal conductivity of the standard pieces, their specific heats are measured by a differential scanning calorimeter. The thermal conductivities are calculated from the data of specific heat, density and thermal diffusivity. To increase the accuracy of data for the thermal diffusivity by data reduction excursion method in the flash method, the governing heat diffusion equation, which is closely described experimental conditions with the finite pulse and the heat loss from the sample surfaces, is solved. In this analysis an integral transform is used.

• Journal of Advanced Marine Engineering and Technology
• /
• 제13권3호
• /
• pp.37-47
• /
• 1989

A calcuation method of the temperature distribution for various shape due to the constant heat input is studied in this paper. So far, the method of try and error is carring out on the mould design. The reason of adopting this method is due to hardly estimate the cooling system in the mould base. As above description, the most part of the mould is supposed as a rectangular, cylinderical and triangular shape and made a governing equation of heat transfer and solved it to numerical analysis by finite-difference method(central- difference). After that in order to confirm that the temperatures are measured on different shape specimens from the part of frequent usage of which are carbon, crome-molybden, tool and stainless steel those were compared with the results of calculations presented in this paper.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 추계학술발표회
• /
• pp.213-216
• /
• 2003

Efforts for better understanding of the interaction between groundwater recharge and thermal regime of the subsurface medium is gaining momentum for its diverse applications in water resources. A numerical model is developed to simulate temperature variations of the subsurface under time varying groundwater recharge. The model utilizes MacCormack scheme for finite difference approximation of the partial differential equation describing the conductive and advective heat transport. For the estimation of recharge rate, optimization of the model is realized by searching for the unknown parameters which minimize the root-mean-square error between simulated and measured temperatures. Simulation results for 22-year time series data of temperature measurements reveal that the proposed model can accurately simulate subsurface temperature variations resulting from the redistribution of the heat due to the movement of water and it can also estimate temporal variations of recharge. Seasonal variations of recharge and a linear relationship between precipitation and recharge are clearly reflected in the simulated results.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1999년도 추계 학술대회논문집
• /
• pp.65-70
• /
• 1999

Radiative heating of a liquid rocket base plane due to plume emission is numerically investigated. Calculation of flow and temperature fields around rocket nozzle precedes and thereby realistic plume shape and temperature distribution inside the plume are obtained. Based on the calculated temperature field, radiative transfer equation is solved by discrete ordinate method. The averaged radiative heat flux reaching the base plane is about $5kW/m^2$ at the flight altitude of 10.9km. This value is small compared with radiative heat flux caused by constant-temperature (1500K) plume emission, but it is not negligibly small. At higher altitude (29.8km), view factor between the babe plane and the exhaust plume is increased due to the increased expansion angle of the plume. Nevertheless, the radiative heating disappears since the base plane is heated to high temperature (above 1000K) due to convective heat transfer.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2011년 춘계학술대회논문집
• /
• pp.100-103
• /
• 2011

In the present work, a numerical study of fluid flow and heat transfer on the concave surface with impinging jet has been performed by solving three-dimensional Reynods-averaged Naver-Stokes(RANS) equations. The constant temperature condition was applied to the concave impingement surface. The inclination angle of jet nozzle and the distance between jet nozzles are chosen as design variables under equivalent mass flow rate of working fluid into cooling channel, and area averaged Nusselt number on concave impingement surface is set as the objective function. Thirteen training points are obtained by Latin Hypercube sampling method, and the PEA model is constructed by using the objective function values at the trainging points. And, the sequential quadratic programming is used to search for the optimal paint from the PBA model. Through the optimization, the optimal shape shows improved heat transfer rate as compared to the reference geometry.

• 대한기계학회논문집
• /
• 제16권2호
• /
• pp.391-399
• /
• 1992

The analysis of the evaporative heat transfer in the inclined porous layer (0.deg.<.theta.<90.deg.) is made by using capillary model. The length of the evaporation zone is obtained numerically by integrating the differential equation using a Runge-Kutta algorithm. As a result, the length of the evaporation zone is inverse proportional to the dimensionless number, E(=Re*.phi./cos.theta.) representing the evaporation intensity, and the relationship of these parameters shows linear in the log graph.

• 대한기계학회논문집B
• /
• 제26권7호
• /
• pp.983-990
• /
• 2002

A numerical analysis has been carried out on forced convection heat transfer in the developing region of a porous channel. The channel is filled with an isotropic porous medium. At the channel walls, a uniform heat flux is given. Comprehensive numerical solutions are acquired to the Brinkman-Forchheimer extended Darcy equation and the LTNE model which does not employ the assumption of local thermal equilibrium between solid and fluid phases. Details of thermal fields in the developing region are examined over wide ranges of the thermal parameters. The numerical solutions at the fully developed region are compared with the previous analytical solutions. The correlation for predicting local Nusselt number in a porous channel is proposed.