• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.954-960
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• 2007

The purpose of this paper is to obtain design method of air-distribution system. Air-distribution system is composed of blower, duct, diffusers and measuring equipment. The air-flow rate from each diffuser is not equal. The air-flow rate is calculated with the combined equations which are Bernoulli's equation, continuity equation and minor loss equations. Inlet condition and outlet condition are adapted in each duct system. Then square difference between function of maximum air-flow rate and minimum air-flow rate is used as an object function. Area of diffuser and velocity are established as constraints. To minimize the object function, the optimization method is used. After optimization the design variables are selected under satisfaction of constraints. The air-distribution system is calculated again with the result of optimized design variable. It is shown that the air-distribution system has the equal air-flow rate from diffusers.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.3
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• pp.257-268
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• 2014

The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity $u=u_0t$ in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.9 no.2
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• pp.45-53
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• 2005

This paper investigates the influence of thermal conductivity and variable viscosity on the problem of micropolar fluid in the presence of suction or injection. The fluid viscosity is assumed to vary as an exponential function of temperature and the thermal conductivity is assumed to vary as a linear function of temperature. The governing fundamental equations are approximated by a system of nonlinear ordinary differential equations and are solved numerically by using shooting method. Numerical results are presented for the distribution of velocity, microrotation and temperature profiles within the boundary layer. Results for the details of the velocity, angular velocity and temperature fields as well as the friction coefficient, couple stress and heat transfer rate have been presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.1049-1056
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• 2005

A conservative pressure-based finite-volume numerical method has been developed for computing flow and heat transfer by using an unstructured grid system. The method admits arbitrary convex polyhedra. Care is taken in the discretization and solution procedures to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are found by a novel second-order accurate spatial discretization. Momentum interpolation is used to prevent pressure checkerboarding and the SIMPLE algorithm is used for pressure-velocity coupling. The resulting set of coupled nonlinear algebraic equations is solved by employing a segregated approach, leading to a decoupled set of linear algebraic equations fer each dependent variable, with a sparse diagonally dominant coefficient matrix. These equations are solved by an iterative preconditioned conjugate gradient solver which retains the sparsity of the coefficient matrix, thus achieving a very efficient use of computer resources.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.4
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• pp.62-75
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• 1991

The purpose of this study is to perform modelings and experiments to measure air flow rate using hot-wires and a CTA(Constant Temperature Anemometer). The flow rate can be obtained by measuring the heat loss of the hot-wire due to the variations of flow velocity when the hot-wire is maintained at uniform temperature. But the defect of this method is that the output signal changes not only by the flow rate but also by the ambient temperature. Thus, in the present study, a method which compensates the variations of the ambient temperature has been introduced to measure exact flow rate. To be more specific, the bridge circuit of the usual hot-wire anemometer system has been modified in such a way that a temperature resistance sensor and a variable resistance are placed in one of the legs to compensate the different temperature coefficients of both the hot-wire and the temperature compensating resistance for flow velocity or for flow mass up to the flow temperature of 50 .deg.C. Comparing the modeling and experimental results, it has been shown that the compensating point differs as the flow rate varies. Therefore, optimum compensation points are sought to construct the circuit. The present modeling and experimental results may be applied to the design of actual air flow meters for automobiles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1066-1073
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• 2006

Recently, because the variable induction systems are adopted to intake system, in-cylinder flow induced by induction system is very complex. Therefore it is very difficult to describe the in-cylinder bulk flow characteristics using the conventional swirl or tumble coefficient. In this study, in order to clarify the 3-D angular flow characteristics of in-cylinder bulk motion in the developing process of variable induction system, we introduced the new 3-D angular flow index, angular flow coefficient($N_B$) Finally, to confirm the index, we carried out the steady flow rig test for intake port of test engine varying valve lift on the test matrix.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1825-1830
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• 2014

Environmental emission of recent automobile is drastically enhanced that it is one of the obvious assignments of exhaust system. This study is a purpose to establish of influence distribution on maxima and minima through the location of pressure on exhaust variable valve. The experiment are checked with real angles using camera which exhaust variable valve is opened side of point. Data has extracted to opening angles with internal flow, pressure. Exhaust variable valve through the floating analysis was analyzed the characteristic of location point about pressure and velocity. The pressures indicated the reduced results internal pressure within muffler. The velocity indicated an opposite results and vibration state of valve was verified to be operated as high speed from lower section. The conclusion to obtain from this study was found out the result to make the optimum back pressure condition as more increasing pressure distribution on valve face if the velocity location attracted by bottom point in order to improve for engine performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.375-385
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• 1996

Turbulent flow and heat transfer characteristics around staggered tube banks were studied using the 3-D Navier-Stokes equations and energy equation governing a steady incompressible flow, which were reformulated in a non-orthogonal coordinate system with cartesian velocity components and discretized by the finite volume method with a non-staggered variable arrangement. The predicted turbulent kinetic energy using RNG $k-{\varepsilon}$ model was lower than that of standard $k-{\varepsilon}$ model but showed same result for mean flow field quantities. The prediction of the skin friction coefficient using RNG $k-{\varepsilon}$ model showed better trend with experimental data than standard $k-{\varepsilon}$ model result. The inclined flow showed higher velocity and skin friction coefficient than transverse flow because of extra strain rate ($\frac{{\partial}w}{{\partial}y}$). Also, this was why the inclined flow showed higher local heat transfer coefficient than the transverse flow.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.92-97
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• 1999

This paper reports by simple method that is quickly corrected the effects of fluid temperature for the hot wire anemometer. We are concerned with a variable output of hot wire anemometer on arbitrary fluid temperature. Hot wire by measuring boundary layer of turbulent flow has been calibrated by arbitrary temperature lower than 10$0^{\circ}C$, and velocity lower than 20m/s. As a result, we could pick up the temperature factor affected by output of hot wire anemometer from related in output of arbitrary temperature to output of room temperature. By using temperature factor on the output of hot wire anemometer, we also obtained that the relationship of velocity was of no effect by temperature of fluids. About results of calibrated hot wire, uncertainly of velocity is 2.15% at room temperature and 3.1% at arbitrary temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.633-640
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• 2003

The present experimental study is focused on the application of multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to guide vane region within diffuser pump. Various different kinds of rotational velocity were selected as experimental condition. Optimized cross correlation Identification to obtain velocity vectors is implemented with direct calculation of correlation coefficients. Fine optical setup concerned with PIV performance is arranged for the accurate PIV measurement of high-speed complex flow. Variable flow pattern are represented quantitatively at the stator region.