• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2432-2437
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• 2007

The demand of high speed and miniaturization of electronic devices results in increased power dissipation requirement for thermal management. In this work, the effects of microchannel width, height and liquid flowrate on the cooling performances of microchannel waterblock are investigated experimentally. The microchannel waterblock considered ranged in width from 0.5 to 0.9 mm, with the channel height being nominally 1.7 to 9 times the width in each case. The experiments were conducted using water, over a liquid flow rate ranging from 0.2 to 2.0 lpm. The base temperature, thermal resistance and pressure drop increase with increasing of liquid flow rate. The measured thermal resistances ranged from 0.10 to 0.23 $^{\circ}C$/W for the channel 5.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.148-154
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• 2004

As a rocket propellent of hydrocarbon fuels, the characteristics of liquefied natural gas was evaluated with the viewpoint of the constituents and content, the cooling performance as a coolant, and characteristic velocity and specific impulse as parameters of the engine performance. Content of methane was a principal factor to determine the characteristics as a rocket propellant and more than 90 % of it was needed as a fuel and coolant in the regenerative cooled liquid rocket engine. Some constituents of the liquefied natural gas can be frozen by the pre-cooling of the pipe lines, therefore they can be a factor disturbing the normal working of engine. In case the content of methane is around 90% in the liquefied natural gas, a normalized stoichiometric O/F mixture ratio of 0.75 is suggested for a nominal operation condition to get the maximum specific impulse and characteristic velocity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.12-15
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• 2011

The most widely used kerosene-LOx liquid-propellant rocket engines in these days have a similar engine schematic to those of the past because of the development cost and the reliability. The efficiency of engines could be increased by the factors such as a cooling method, engine cycles, shape of cooling channels, additional coolant and so on. In this article, it is described that some design ideas for performance enhancement by exchange kerosene with LOx of a coolant.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.2
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• pp.246-254
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• 2017

In this paper, cooling characteristics of seeker windows were examined using the Sinda-Fluint software. Various cooling methods were considered to satisfy the limit temperature of the cooled seeker window which would be exposed to excessive aerodynamic heating conditions by varying coolant type and mass flow rate of coolant. Due to the enhanced heat transfer between the coolant and the seeker window, internally cooled seeker window which uses liquid coolant showed lowered temperature distribution in the window compared to internally cooled seeker window which uses gas coolant. External film cooled seeker window also showed good cooling characteristics because it reduces the convective heat flux to the seeker window fundamentally. It was also confirmed that the temperature and the temperature gradient of seeker windows were significantly reduced for the cases which use external film cooling additionally to the gas and liquid cooled seeker window.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.147-150
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• 2007

In this study, cooling characteristics of combustion gas were investigated by injecting liquid nitrogen into liquid rocket combustion chamber. A injection ring of liquid nitrogen was installed between a combustion chamber and a mixing chamber which was designed for mixing of combustion gas and nitrogen. At first, a ignition test of liquid rocket engine was conducted to verify a stable combustion process and 10 second combustion tests were successfully conducted. The results showed that combustion gas of LRE could be cooled by using liquid nitrogen.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.104-104
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• 2015

Due to the demand of the cold neutron flux in the neutron science and beam utilization technology, the cold neutron source (CNS) has been constructed and operating in the nuclear research reactor all over the world. The majority of the heat load removal scheme in the CNS is two-phase thermosiphon using the liquid hydrogen as a moderator. The CNS moderates thermal neutrons through a cryogenic moderator, liquid hydrogen, into cold neutrons with the generation of the nuclear heat load. The liquid hydrogen in a moderator cell is evaporated for the removal of the generated heat load from the neutron moderation and flows upward into a heat exchanger, where the hydrogen gas is liquefied by the cryogenic helium gas supplied from a helium refrigeration system. The liquefied hydrogen flows down to the moderator cell. To keep the required liquid hydrogen stable in the moderator cell, the CNS consists of an in-pool assembly (IPA) connected with the hydrogen system to handle the required hydrogen gas, the vacuum system to create the thermal insulation, and the helium refrigeration system to provide the cooling capacity. If one of systems is running out of order, the operating research reactor shall be tripped because the integrity of the CNS-IPA is not secured under the full power operation of the reactor. To prevent unscheduled reactor shutdown during a long time because the research reactor has been operating with the multi-purposes, the introduction of the standby cooling system (STS) can be a solution. In this presentation, the design considerations are considered how to design the STS satisfied with the following objectives: (a) to keep the moderator cell less than 350 K during the full power operation of the reactor under loss of the vacuum, loss of the cooling power, loss of common electrical power, or loss of instrument air cases; (b) to circulate smoothly helium gas in the STS circulation loop; (c) to re-start-up the reactor within 1 hour after its trip to avoid the Xenon build-up because more than certain concentration of Xenon makes that the reactor cannot start-up again; (d) to minimize the possibility of the hydrogen-oxygen reaction in the hydrogen boundary.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.235-240
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• 2010

Transpiration cooling is the most effective cooling technique for liquid rocket and air-breathing engines operating in aggressive environments with higher pressures and temperatures. Combustor liners and turbine vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. However, its practical implementation has been hampered by the limitations of available porous materials. The search for more practical methods of increasing the internal heat transfer within the walls has led to the development of multi-laminate porous structures, such as Lamilloy$^{(R)}$ and Transply$^{(R)}$. This paper reviews recent research activities of transpiration cooling for the propulsions of liquid rocket, gas turbine, and scramjet.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.133-139
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• 2009

An analysis has been performed on the specific impulse for a liquid rocket engine of gas generator cycle. The present analysis method has been validated through the comparison of the optimal specific impulse for the 300t thrust conceptual engine against the published data. The engine specific impulse can be increased by applying film coolant decreasing the fuel pump head for regenerative cooling despite the decrease of specific impulse of the combustion chamber when the film coolant participates combustion more than the critical amount. The improved condition shows that higher combustion chamber pressure is achieved with less fuel pump head rise by additional film cooling.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.601-604
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• 2010

An experimental study was carried out to investigate the effect of film cooling in a liquid rocket engine using Hydrogen peroxide/Kerosene as propellants. The heat fluxes were calculated by the measured wall temperatures on the axial direction of thrust chamber for mass flow rate of coolant and different type of film cooling rings. The flow rate of coolant was 0~20 percent of the total propellant.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.324-329
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• 2008

The liquid cooling effect of a natural convection type radiator by using the PCM has been investigated experimentally. The radiator size is $423{\times}295{\times}83$ mm and PCM container size is $398{\times}270{\times}26$ mm. The objective is elapsed time higher than maximum time to reach for maximum operating temperature of a general liquid cooling radiator. This study, in order to study on the effects of the phase-change phenomenon, carried out the various mass flow rate, input electric power, ambient and melting point of three type PCM. For the above experimental parameter, the melting time was performed about 180/250/560 min at input power 150 W and ambient $30^{\circ}C$ from using the three type PCM(PCM_S1/S2/S3) respectively. Furthermore, the effects of the thermal dissipation was decreased higher input power than lower input power at heating block and melting time of PCM. However, the effects of mass flow rate did not nearly affect of the thermal performance especially.