• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1226-1231
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• 2009

This paper presents operating characteristics of internal heat exchanger(IHX) for $CO_2$ geothermal heat pump in the heating mode. Mass flow rate of $CO_2$, inlet temperatures of $CO_2$ at high and low pressure side were selected as main effect factors by using fractional factorial DOE(Design of Experiments). And RSM(Response Surface Method) was used in optimization phase. The results show that heat transfer rate of IHX increases when either inlet temperature of low pressure side decreases or inlet temperature of high pressure side increases. Effectiveness of IHX increases with increasing of inlet temperature of either high pressure side or low pressure side. Finally, performance contour map was provided over the operation ranges of the main design factors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.931-937
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• 2008

A high motive pressure thermal vapor compressor(TVC) for a commercial multi-effect desalination(MED) plant is designed to have a high entraining performance and its robustness is also considered in the respect of operating stability at the abrupt change of the operating pressures like the motive and suction steam pressure which can be easily fluctuated by the external disturbance. The TVC having a good entraining performance of more than entrainment ratio 6.0 is designed through the iterative CFD analysis for the various primary nozzle diameter, mixing tube diameter and mixing tube length. And then for a couple of TVC having a similar entrainment ratio, the changes of the entrainment ratio are checked along the motive and suction pressure change. The system stability is diagnosed through the analyzing the changing pattern of the entrainment ratio.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.303-310
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• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.7
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• pp.649-658
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• 2000

Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.515-519
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• 2012

A numerical study was performed to observe the relation between internal flow characteristics and operating temperatures in a Lapple cyclone. The present numerical results agree reasonably well with previous experimental and numerical results. As the operating temperature increases, the pressure drop decreases due to decrease of wall shear stress and tangential velocities. A detailed comparison of pressure drops in the cyclone between theoretical prediction models and the present numerical simulations is also presented for wide range of operating temperatures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.640-647
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• 2002

An experimental investigation or the sonic and supersonic air ejector systems has beer conducted to develop design and prediction programs for practical ejector system. Five different primary nozzles have been employed to operate the ejector systems in the ranges of low and moderate operating pressure ratios. The ejector operating pressure ratio for the secondary chamber pressure to be minimized has a strong influence of the ejector throat ratio. The pressure inside the ejector diffuser is not dependent on the primary nozzle configurations employed but only a function of the ejector operating pressure ratio. Experimental results show that a supersonic ejector system is more desirable for obtaining high vacuum pressure of the secondary chamber than a sonic ejector system.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.395-402
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• 1993

A newly designed torsion pendulum operating at high pressures and various temperatures has been constructed. The High Pressure Torsion Pendulum(HPTP) is capable of containing gaseous pressure to 690MPa(100, 000psi) and operating at temperatures from-$100^{\circ}C$ to $300^{\circ}C$. A glass fiber braid is installed between two sample holders to accommodateliquid samples. The HPTP was fully automated and computerized using an IBM-AT personal computer to control initiation of oscillation, collect digitized data, and calculate the shear and loss moduli from damped curves, The curing process of an epoxyamine(DGEBA-DDS) system under various pressures up to 124 MPa(18, 000 psi) at $150^{\circ}C$has been successfully carried out and some results are presented.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1294-1299
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• 2009

Since the operating pressure of $CO_2$ gascooler is so high compared with that of previous subcritical condenser, the optimization of gascooler is needed for improve heat exchanger performance. In this study, the performance characteristics of five kinds of heat exchangers were analyzed and compared with operating conditions. As a result, the 4-20 HX-tube shows the maximum gascooler capacity because the heat transfer is effective and pressure drop is small. Beside, the high performance of 4-20 HX-tube could be keep for wide operating condition.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.691-698
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• 2020

In this study, the effects of hydrodynamic interceptors on a high-speed vessel were investigated to identify the operating principle based on experiments. Model tests were performed using a high-speed towing carriage. The resistance, trim and rise of Center of Gravity (CG) of the high-speed vessel were measured for various ship speeds and interceptor heights. As the interceptor height increased, the trim and rise of CG were reduced. In order to quantitatively analyze these phenomena, the pressure at the stern bottom was measured using tactile sensors. The reliability of the measured results from the tactile sensors was verified through repeat tests. The pressure on the stern bottom increased in proportion to the interceptor height, as the interceptor partially blocked the flow there. Then, the trim was reduced. However, as the ship speed increases, the pressure at the location close to the interceptor decreases when the interceptor height is small, leading to increased trim. Therefore, the interceptor height for running attitude control should be carefully determined considering multiple factors in the operating condition of the high-speed planing hull.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.74-80
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• 1984

In the reduction gears for marine propulsion engine such as turbine or high speed diesel engine, the standard involute double helical gears are generally used. However the addendum modification gear can be used in the reduction gear as it has flexibility for gear design on the tooth strength, scoring and operating noise. In this case, the determination of gear shaft bearing load is difficult by the alternation of operating pressure angle. In this paper, the formulas of bearing load according to the arrangements of the reduction gears are derived and the diagrams of operating pressure angle according to the modification coefficient are presented.