• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.7 no.2
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• pp.73-79
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• 1978

This paper presents the experimental study on the design conditions of pressure between booster ejector and air ejector in the steam-jet water-vapour refrigeration system. In this experiment, the motive steam of booster ejector and ai. ejector was dry saturated from 6 ata to 8 ata and flash chamber pressure were about $10\∼540mmHg$ higher than mixing section in booster ejector. The investigation of air on the pressure of booster ejector was performed by changing the condenser pressure. The experimental results show that flash chamber vacuum and condenser pressure of steam-jet refrigeration cycle increased in accordance with the increase of motive steam Pressure. Among the several nozzle sires tested, No.4 nozzle were best in term of evaporator vacuum under the constant operating conditions of air ejector in condenser.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.987-995
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• 2019

Steam jet condensation is of great importance to pressure suppression containment and automatic depressurization system in nuclear power plant. In this paper, the condensation processes of sonic steam jet in a quiescent subcooled pool are recorded and analyzed, more precise understanding are got in direct contact condensation. Experiments are conducted at atmospheric pressure, and the steam is injected into the subcooled water pool through a vertical nozzle with the inner diameter of 10 mm, water temperature in the range of $25-60^{\circ}C$ and mass velocity in the range of $320-1080kg/m^2s$. Richardson number is calculated based on the conservation of momentum for single water jet and its values are in the range of 0.16-2.67. There is no thermal stratification observed in the water pool. Four condensation regimes are observed, including condensation oscillation, contraction, expansion-contraction and double expansion-contraction shapes. A condensation regime map is present based on steam mass velocity and water temperature. The dimensionless steam plume length increase with the increase of steam mass velocity and water temperature, and its values are in the range of 1.4-9.0. Condensation heat transfer coefficient decreases with the increase of steam mass velocity and water temperature, and its values are in the range of $1.44-3.65MW/m^2^{\circ}C$. New more accurate semi-empirical correlations for prediction of the dimensionless steam plume length and condensation heat transfer coefficient are proposed respectively. The discrepancy of predicted plume length is within ${\pm}10%$ for present experimental results and ${\pm}25%$ for previous researchers. The discrepancy of predicted condensation heat transfer coefficient is with ${\pm}12%$.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.238-242
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• 2015

A steam jet vacuum system that will be implemented in a multi-effect desalination plant is numerically investigated. The objective of this study is to numerically investigate the performance characteristic of the steam jet vacuum system for the sea water distillation process. The effects of design parameter such as nozzle size and converging duct angle are discussed in order to get a better understanding of flow characteristics inside the steam ejector and subsequently pave the way for more optimum designs. The simulation results have been in good agreement with experimental data and have well reproduced the shock train phenomena of the throat region.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.41-46
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• 2006

This study shows a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water by about $5^{\circ}C\;from\;25^{\circ}C$ or higher. In this research, to replace the present water cooling system, we focused on a water cooling system by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are depended on the vacuum pressure in the enclosed tank, and the cooling water is generated by latent head of evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8$ mmHg using a steam driven ejector with jet condenser.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.349-356
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• 2001

Phenomenon of direct contact condensation (DCC) heat transfer between steam and water is characterized by the transport of heat and mass through a moving steam/water interface. Since the DCC heat transfer provides some advantageous features in the viewpoint of enhanced heat transfer, it is widely applied to the diversified industries. This study proposes a simple condensation model on the stable steam jets discharging into a quenching tank with subcooled water from a single horizontal pipe for the prediction of the steam jet shapes. The model was derived from the mass, momentum and energy equations as well as thermal balance equation with condensing characteristics at the steam/water interface for the axi-symmetric coordinates. The extremely large heat transfer rate at the steam/water interface was reflected in the effective thermal conductivity estimated from the previous experimental results. The results were compared with the experimental ones. The predicted steam jet shape(i. e. radius and length) by the model was increasing as the steam mass flux and the pool temperature were increasing, which was similar to the trend observed in the experiment.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.51-59
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• 2017

Steam jets ejected from a rupture zone of high energy pipes may cause damage to adjacent structures. This event could lead to more serious accidents in nuclear power plants. Therefore, to prevent serious accidents, high energy pipes of nuclear power plants are designed according to the ANSI / ANS 58.2 technical standard. However, the US Nuclear Regulatory Commission (USNRC) has recently pointed out non-conservatism in existing high energy pipe fracture evaluation methods, and required the assessment of the unsteady load of the jet caused by a potential feedback mechanism as well as the impact range of steam jet, the jet impact loads and the blast wave effects at the initial breakage stage. The potential feedback mechanism refers to a phenomenon in which a vortex formed by impingement jets amplifies vortex itself and induces jet vibration in a shear layer. In this study, CFD methodology using the LES turbulence model is established and numerical analysis is carried out to evaluate the dynamic behavior of impingement jets and the potential feedback mechanism during jet impingement. Obtained results have been compared with an empirical correlation and experiment.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.479-484
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• 2000

For the purpose of a cost effective design of practical subsonic/supersonic ejector systems, an experiment was carried out using a superheated steam as a primary driving flow. The superheated steam jet was produced by several different kinds of subsonic and supersonic nozzles. The secondary flow of atmospheric air inside a plenum chamber was drawn into the primary steam jet. The vacuum performance of the plenum chamber was investigated for a wide range of the ejector operation pressure ratio. The result showed that the static pressure of the mixed flow at the ejector throat is only a function of the ejector operation pressure ratio, regardless of the primary nezzle type employed.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.72-86
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• 2016

A steam explosion may occur during a severe accident, when the molten core comes into contact with water. The pressurized water reactor and boiling water reactor ex-vessel steam explosion study, which was carried out with the multicomponent three-dimensional Eulerian fuel-coolant interaction code under the conditions of the Organisation for Economic Co-operation and Development (OECD) Steam Explosion Resolution for Nuclear Applications project reactor exercise, is presented and discussed. In reactor calculations, the largest uncertainties in the prediction of the steam explosion strength are expected to be caused by the large uncertainties related to the jet breakup. To obtain some insight into these uncertainties, premixing simulations were performed with both available jet breakup models, i.e., the global and the local models. The simulations revealed that weaker explosions are predicted by the local model, compared to the global model, due to the predicted smaller melt droplet size, resulting in increased melt solidification and increased void buildup, both reducing the explosion strength. Despite the lower active melt mass predicted for the pressurized water reactor case, pressure loads at the cavity walls are typically higher than that for the boiling water reactor case. This is because of the significantly larger boiling water reactor cavity, where the explosion pressure wave originating from the premixture in the center of the cavity has already been significantly weakened on reaching the distant cavity wall.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.26-32
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• 2014

In this study, DC (Direct current) type steam plasma igniter is developed for effective ignition of high-energy density metal aluminum and gas temperature is measured by emission spectrum of OH radical. Because of the ultra-high gas temperature, the DC plasma jet is measured by Boltzmann plot method which is the non-contact optical technique and spectrum comparison-analysis. And both methods were applied to experiment after accurate verification. As a result, we could identify that plasma jet temperature is 2900 K ~ 5800 K in the 30 mm range from the nozzle tip.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.120-127
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• 2017

High temperature oxygen and water vapor was generated from catalytic decomposition of rocket grade highly concentrated hydrogen peroxide, and monopropellant thruster system was developed and applied into space propulsion system. In this research, background research and conceptual design of underwater propulsion system using catalytic decomposition of hydrogen peroxide was progressed. Two types of system was designed with different steam injection methods. Propulsion system that has ring-type steam injector was manufactured and performance estimation of system was performed with different nozzle exit area. Performance evaluation with central steam injection type jet engine will be progressed in the future.