• Journal of Power System Engineering
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• v.10 no.4
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• pp.31-37
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• 2006

In this study, the ability for the function of double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for the circulating of liquid of high temperature and high pressure and low temperature and low pressure at the same time is presented. And in this double pipe, liquid pipe of high temperature and pressure is used to connect condenser and expansion valve and gas pipe of low temperature is used to connect evaporator and compressor. Also, when liquid refrigerant of high temperature and gas refrigerant of low temperature is circulated by reversed flow in the double pipe. The contribution of liquid gas heat exchange pipe is studied by comparison of the effect of heat transfer by temperature difference when liquid pipe and gas pipe is installed separately.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.702-708
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• 2006

This study shows the experimental characteristics of the double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for circulating of a liquid of high temperature, pressure and a gas of low temperature, pressure at the same time. So the functions of pipe and pipe's expansion and heat transfer are presented simultaneously. In the result, the temperature of gas refrigerant at the inlet of compressor increased about $5^{\circ}C$ by the heat transfer with liquid refrigerant in case of the double pipe. And liquid gas refrigerant which the temperature at the inlet of evaporator decreased about $3^{\circ}C$ comparing with the existing type flows into an evaporator COP of the double pipe increased about $7{\sim}10%$ comparing with that of the conventional pipe. And the noise of the double pipe at capillary tube is less than that of the conventional type about 3dB. Consequently. it is convinced the superiority of the double pipe in the heat loss and soundproofing aspect.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1087-1094
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• 2005

This paper presents the validity and limitation of the thin-shell approach for the analysis of elastic wave propagation in a pipe with nonviscous liquid. The phase velocities calculated by the thin-shell approach were compared with those calculated by the thick-cylinder approach. In contrast to the case of the empty pipe, where only two modes were obtained and the first mode was calculated in a limited frequency range, the results for the liquid-filled pipe exhibits a large number of modes due to the large number of branches of the apparent liquid mass. Several of the lowest modes of the waves in a liquid-filled pipe were calculated for various pipe thicknesses in a low frequency range. The thin-shell approach was valid for a reasonable range of pipe thicknesses.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.6
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• pp.583-593
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• 2003

The effect of liquid confined in a pipe on elastic waves propagating in the pipe wall was studied theoretically and experimentally. The axisymmetric motion of the wave was modeled with the cylindrical membrane shell theory. The liquid pressure satisfying the axisymmetric wave equation was included in the governing equation as a radial load. The phase speed of the wave propagating in the axial direction was calculated, accounting for the apparent mass of the liquid. Experiments were performed in a pipe equipped with ring-shaped, piezoelectric transducers that were used for transmitting and receiving axisymmetric elastic waves in the pipe wall. The measured wave speeds were compared with the analytical ones. This work demonstrates the feasibility of using pipe waves for the determination of the density and, eventually, the flow rate of the liquid in a pipe.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2123-2128
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• 2004

In this study, analysis is made for the effects of groove shape on the thermal performance of a axial groove heat pipe. The mathematical models of two-phase flow in grooved heat pipe are presented for the capillary limitation in steady state. Generally, the heat pipe performance depends on the capillary pressure and liquid flow. The friction force of liquid flow through the groove increases with the groove width decreased, and then the capillary pressure is improved in the gas-liquid interface of groove. Therefore, the optimal groove width shaper exists for the maximum thermal performance of heat pipe. In this paper, the optimal groove shape and scale are presented by considering both capillary pressure and liquid flow.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1159-1167
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• 2000

Particles in liquid-solid suspension flow might enhance or suppress the rate of heat transfer and turbulence depending on their size and concentration. The heat transfer characteristics of liquid-solid suspension in turbulent flow are not well understood due to the complexibility of interaction between solid particles and turbulence of the carrier fluid. In this study, the heat transfer coefficients of liquid-solid mixtures are investigated using a double pipe heat exchanger with suspension flows in the inner pipe. Experiments are carried out using spherical fly ash particles with mass median diameter ranging from 4 to $78{\mu}m$. The volume concentration of solids in the slurry ranged from 0 to 50% and Reynolds number ranged from 4,000 to 11,000. The heat transfer coefficient of liquid-solid suspension to water flow is found to increase with decreasing particle diameter. The heat transfer coefficient increases with particle volume concentration exhibiting the highest heat transfer enhancement at the 3% solid volume concentration and then gradually decreases. A correlation for heat transfer to liquid-solid flows in a horizontal pipe is presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.366-372
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• 2001

The ice plugging process consists of placing liquid nitrogen around a pipe and removing heat until the water in the pipe freezes and provides a solid plug or seal against fluid movement. This technique enables us to repair or inspect a pipe system without shutdown of entire system. A set of test apparatus for investigation of the liquid freezing phenomena during ice plugging is prepared. This study shows the characteristics of the liquid freezing and the heat transfer with various pipe and freezing jacket conditions. And in case there is flow of the fluid inside the pipe, the flow rate which can be able to form the ice plug is identified with the effect of the pipe diameter and freezing jacket length on the plug formation. The permissible maximum flow rate for the complete plug formation is approximately proportional to the freezing jacket length at the same pipe diameter condition.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.360-364
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• 2001

Numerical Aanlysis is made on the thermal performance of micro heat pipe in a axial flat grooved channel. The flow of liquid and vapor is investigated in trapezoidal grooves and the effect of variable shear stress along the interface of the liquid and vapor considered. The results from this study are obtained in the axial variation of pressure difference between vapor and liquid, contact angle, velocity of liquid and vapor and so forth. In addition, maximum heat transport capacity of micro-heat pipe is provided by varying the operation temperature, and compared with that from Schneider and Devos's model in which the interfacial shear stress is neglected.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.386-391
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• 2001

In this paper, the vibration characteristics of IHTS(Intermediate Heat Transfer System) piping system of LMR(Liquid Metal Reactor) conveying hot liquid sodium are investigated to eliminate the pipe supports for economic reasons. To do this, a 3-dimensional straight pipe element and a curved pipe element conveying fluid are formulated using the dynamic stiffness method of the wave approach and coded to be applied to any complex piping system. Using this method, the dynamic characteristics including the natural frequency, the frequency response functions, and the dynamic instability due to the pipe internal flow velocity are analyzed. As one of the design parameters, the vibration energy flow is also analyzed to investigate the disturbance transmission paths for the resonant excitation and the non-resonant excitations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.6 s.237
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• pp.747-754
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• 2005

Because the liquid-vapor interfacial shear stress affects seriously the liquid flow and the maximum heat transport rate of the grooved wick heat pipe, an accurate modeling for the pressure drop characteristics of the liquid flow is required. A novel method for calculating the liquid pressure drop and the velocity profile of an open channel flow in a microchannel with an arbitrary cross-section is suggested and validated by experiments. An experimental apparatus for the Poiseuille number of the liquid flow in open rectangular microchannels with the hydraulic diameters of 0.40mm, 0.43mm, 0.48mm is used in order to reproduce real situations in the grooved wick heat pipe. Analytic results from the suggested method are compared with the experimental data and they are in a close agreement with each other.