• Advances in materials Research
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• v.9 no.1
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• pp.15-32
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• 2020

In this article, an analytical solution is presented for the steady-state axisymmetric thermal stress distributions in a composite hollow cylinder. The cylinder is composed of two isotropic and anisotropic materials which is subjected to the thermal boundary conditions of convective as well as radiative heating and cooling on the inner and outer surfaces, respectively. The solution of the temperature is obtained by means of Bessel functions and the thermal stresses are developed using Potential functions of displacement. Numerical results are derived for a cylinder which is similar to a gas turbine combustor and showed that the maximum temperature and thermal stresses (radial, hoop, axial) occurred in the middle point of cylinder and the values of thermal stresses in anisotropic cylinder are more than the isotropic cylinder. It is worthy to note that the values of the thermal conditions which estimated in this research, not to be presented in any other papers but these values are very accurate in calculation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.440-448
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• 1998

This paper considers the influence of circumferential wall heat conduction for the case of forced convection around a circular cylinder in cross flow of air. Keeping uniform heat generation from the inner surface of the cylinder in radial direction, heat is transferred by wall conduction in the circumferential direction due to the asymmetric nature of the temperature distribution of the cylinder and by convection around the perimeter of the cylinder. The wall conduction depends on conductivity of the cylinder and size of the cylinder radius and thickness and affects the local convective heat transfer rate significantly for geometrically similar surfaces and flow conditions. A nondimensional conjugation parameter K. (=k$_t$R/k$_w$b) has been used to characterize the effect of the circumferntial wall heat conduction. The small values of conjugation parameter K are found to be associated with large effect of wall conduction on the local convective heat transfer rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.4
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• pp.279-287
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• 1990

An experimental study of the heat transfer characteristics between circular water jet and cylindrical inner surface is presented. The ratios of the semi-cylinder's inner diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that cirucmferential distribution of the heat transfer coefficient peaked at the stagnation point and, there occurred a kind of a secondary maximum of heat transfer that moved toward to stagnation point as the ratio d/D increased. The local heat transfer coefficient increases as the Reynolds number becomes larger, and the rate of increase is subjected to the influence of d/D & position of angle. Also, optimum heights of supplementary water which brings about the augmentation of heat transfer are S/D=1 for the stagnation point, the position of $15^{\circ}$ & $30^{\circ}$ angle, but for the positions of $45^{\circ}$ angle (d/D=10~11.67), $60^{\circ}$ & $75^{\circ}$ angle, the heat transfer coefficients in the case of using supplementary water are smaller than simple jet (S/D=0).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.754-763
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• 2005

This paper introduces a new concept compressor in which piston orbits in the cylinder having an annular space formed between two concentric circular walls. In this configuration, two gas pockets are formed with $180^{\circ}$ phase difference: one between the wrap of the orbiting piston and the inner cylinder wall and the other between the piston wrap and the outer cylinder wall. This alternating feature of gas compression and discharge processes yields several advantages such as low torque variation and low gas pulsation. Computer simulation program has been developed to evaluate the compressor performance. The volumetric, adiabatic, and mechanical efficiencies of the orbiter compressor are calculated to be $85.6\%,\;97.2\%,\;and\;95.2\%$, respectively, when it is used as an air compressor.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.7-13
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• 2007

Numerical analysis is carried out for combined heat transfer in an indirected NIR(Near Infrared Ray) heating chamber. Reynolds number and shapes of absorbed cylinder are known as important parameters on the combined heat transfer effects. Reynolds number based on the outer diameter of the cylinder is varied from $10^3$ to $3{\times}10^5$. Four difference heat transfer regimes are observed: forced convection and radiative heat transfer on the outer surface of the cylinder, pure conduction in the cylinder body, pure natural convection and radiation between lamp surface and inner surface of the cylinder, and radiation from the lamp. Flow and temperature characteristics are presented with iso-contour lines for the absorbed circular and elliptic cylinders to compare their differences. The convective and radiative heat transfer fluxes are also compared with different Reynolds numbers. As usual, Reynolds number is an important factor to estimate increasing convective heat transfer as it increases. The shape of absorbed cylinder results overall heat transfer rates remain unchanged.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.935-942
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• 2014

A numerical analysis of the effect of the Prandtl number on the natural convection in a cold outer tilted square enclosure with an inner hot circular cylinder is presented. Several Prandtl numbers (Pr=0.1, 0.7, 7) are considered, with different angles($0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$) for the enclosure and Rayleigh numbers ($Ra=10^3$, $10^4$, $10^5$). The effect of the Prandtl number on the natural convection is analyzed using isotherms and streamline and surface-averaged Nusselt numbers. The flow and heat transfer characteristics are found to be dependent on the time for $Ra=10^5$ and Pr=0.1 at angles of $0^{\circ}$ and $45^{\circ}$. However, in the other cases, the flow and heat transfer characteristics are independent of the time.The surfaceaveraged Nusselt number increases with an increase in the Prandtl number. As the Prandtl number increases, the Nusselt number becomes larger regardless of the angle for $Ra=10^5$. In particular, the Nusselt number steeply increases when the angle is $45^{\circ}$ for $Ra=10^5$ and Pr=0.1.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.396-410
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• 2020

The design and the construction are carried out by installation of new caissons on the back or the front of existing caissons to increase the stability of existing caisson breakwater. In this study, we use the eigenfunction expansion method to analyze the effects of wave structure interaction when new porous dual circular caissons are installed on the back or the front of existing breakwater. The porous dual circular caisson which consisting of a porous outer cylinder circumscribing an impermeable inner cylinder is one type of seawater exchanging breakwater. The comparison of numerical results between present method and Sankarbabu et al. is made, and the wave force and the wave run-up acting on each porous dual circular caisson are calculated for various parameters by considering the wave structure interaction.

• Korean Journal of Bronchoesophagology
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• v.16 no.2
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• pp.131-137
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• 2010

Background: Montgomery T-tube is widely used to maintain airway in many cases. Market-available tubes are not always fit to the trachea of each patient and need some modification such as trimming. Complications do happen in prolonged use like tracheostomy tubes. To overcome above limitations, we designed custom-made T-tube using CT data with the aid of 3D reconstruction software. Material and Method: Boundaries were extracted from neck CT data of normal person and processed by surface rendering methods. Real laryngotracheal model and tracheal inner surface-mimicking tube model were made with plaster and rubber. The main tube was designed by accumulation of circles or simple closed curves made from boundaries. Stomal tube was made by accumulation of squares due to limitation of software. Measurement data of tracheal lumen were used to custom-made T-tubes. Tracheal lumen residing portion (vertical limb) was made like circular cylinder or simple closed curved cylinder. Stomal portion (horizontal limb) was designed like square cylinder. Results: Custom made T-tube with cylindric vertical limb and horizontal limb of square cylinder was designed. Conclusion: CT data was helpful in making custom made T-tube with 3D reconstruction technique. If suitable materials are available, commercial T-tube can be printed out from 3D printers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.649-658
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• 1996

Small-amplitude harmonic oscillations of multi-cylinders are considered both experimentally and theoretically. For the theoretical model, the flow regime is separated into inner and outer regions. In the inner region, the flow is governed by the generalized Stokes boundary layer equation. In the outer region, the full Navier-Stokes equation for the steady streaming flow is solved numerically by using ADI scheme and FVM coupled with the boundary integral method. Flow visualization experiments are conducted by using the Laser Sheet Image Technique. The case of two circular cylinders and square cylinders with variable distances are chosen as a typical example. Although experimental results are based on the flow in the finite domain, both experimental and numerical results agree well qualitatively. As the separation of cylinders is increased, a numerical result shows the asymptotic convergence to a single cylinder case.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.4
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• pp.13-20
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• 1980

The integral equation method to solve the boundary-value problem of a 2-dimensional body oscillating in the presence of a free surface generally breaks down at and near irregular frequencies due to the hypothetical flow inside the body. In this paper singularity distributions were extended to an inner free surface to remove the irregular frequency as Ohmatsu's work in 1978, and the solution for the above problem was found by using stream function. For various bodies including Lewis form cylinders, the hydrodynamic forces were calculated numerically at various wave numbers. From the results we concluded that the irregular frequencies can be removed even for the Lewis form cylinder as Ohmatsu done for circular cylinders, and calculated hydrodynamic forces by the present method are little higher than those of Ohmatsu's when the singularities are put on the inner free surface of the body. We specially point out that the solution for heaving motion converges in an oscillatory manner but not for swaying and rolling motions.