• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.415-424
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• 2004

Cooling the electronic equipment is one of the major focal points of the design process and the key to successful product launch. The two-phase loop thermosyphone which is a good candidate among many available options was investigated fur cooling of the high power amplifiers. The system is composed of evaporator which contains 6 parallel cold plates, fan cooled condenser, gas-liquid separator, and interconnecting tubes. Experiments were performed for several refrigerant charging values, hs and as a experiment result, the optimum charging value fur this system was proposed. In order to optimize the system design, the operating cycle pressure and inlet/outlet temperatures of evaporator and condenser are measured and analyzed. The effect of the three parameters such as flow rate and temperature of condenser cooling air, and thermal load on the evaporator are investigated. The lower the operating pressure and the cycle temperatures are also better to prevent the leakage of the system. The system invesigated in this paper can be directly used for cooling of a real unmanned wireless communication station.

• Journal of Mechanical Science and Technology
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• v.14 no.1
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• pp.121-129
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• 2000

The thermal performance of a flat evaporator for capillary pumped loop (CPL) applications was investigated. Two to four layers of coarse wire screen wicks were placed onto the heated surface to provide irregular passages for vapor flow. The evaporator and condenser were separated by a distance of 1.2 m and connected by individual liquid and vapor lines. The wall material was copper and the working fluid was ethanol. The experimental facility utilized a combination of capillary and gravitational forces for liquid return, and distribution over the evaporator surface. The tubing used for vapor and liquid lines was 9.35 mm or less in diameter and heat was removed from the condenser by convection of air. A heat flux of up to $4.9{\times}10^4$ $W/m^2$ was applied to a flat evaporator having dimensions of 100 mm by 200 mm, 20 mm thick. The thermal resistance of the system as well as the temperature characteristics of the system was investigated as the evaporator heat flux and the condenser cooling capacity varied. The performance of the evaporator and effect of condenser cooling capacity were analyzed and discussed.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1261-1266
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• 2008

Experimental study was performed to understand the operations of a showcase working in a discount store. Temperatures of evaporation, condenser were measured and also electric power consumption of compressor were measured. The purpose of this study is to application use of cold-heat storage systems operated the showcase. At the condition using ice storage system, the ice making process was operated during midnight being not needed the cooling of the showcase through the continuous running of the condenser unit. And then, the refrigerant was sub-cooled using stored cold-heat after being discharged from the air cooling condenser during the day time. The cooling performance was increased owing to the sub-cooling of refrigerant during day time, hence the running time of the compressor was effectively decreased. In other words, this study showed that power consumption during daytime can be transferred to the midnight for making use of the refrigerant sub-cooling. So the operating characteristics of the showcase system under various working conditions were analyzed and discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.738-744
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• 2006

In order to utilize the condensation heat of refrigerants in condenser on the absorption chiller system, the solution cooled condenser (SCC) was proposed using the weak solution of absorber as a cooling medium. The increase of COP with the increase of UA of the solution cooled condenser was approximately 0.009 in maximum with single effect one, and is about maximum 0.008 in occasion of double effect one with series flow compared to that without. In the case of heat exchanger, effectiveness is about 0.85, it's increments are 0.008 and 0.0072, respectively. And solution cooled condenser is more effective device in the single effect absorption system than double effect system for the principle of operation. On the other hand, as the solution split ratio increases when the value of UA is fixed, COP is increased and as the solution split ratio increases when the value of UA is fixed, COP is increased. If the flow rate of cooling water or the value of UA is reduced in order to increases the heat recovery of solution cooled condenser, heat recovery of solution cooled condenser is increased a little but COP is decreased as the system pressure is increased.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.358-363
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• 1995

A study on passive cooling systems for concrete containment of advanced pressurized water reactors has been performed. The proposed passive containment cooling system (PCCS) consist of (1) condenser units located inside containment, (2) a steam condensing pool outside containment at higher elevation, and (3) downcommer/riser piping systems which provide coolant flow paths. During an accident causing high containment pressure and temperature, the steam/air mixture in containment is condensed on the outer surface of condenser tubes transferring the heat to coolant flowing inside tubes. The coolant transfers the heat to the steam condensing pool via natural circulation due to density difference. This PCCS has the following characteristic: (1) applicable to concrete containment system, (2) no limitation in plant capacity expansion, (3) efficient steam condensing mechanism (dropwise or film condensation at the surface of condenser tube), and (4) utilization of a fully passive mechanism. A preliminary conceptual design work has been done based on steady-state assumptions to determine important design parameter including the elevation of components and required heat transfer area of the condenser tube. Assuming a decay power level of 2%, the required heat transfer area for 1,000MWe plant is assessed to be about 2,000 ㎡ (equivalent to 1,600 of 10 m-long, 4-cm-OD tubes) with the relative elevation difference of 38 m between the condenser and steam condensing pool and the riser diameter of 0.62 m.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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• pp.408-417
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• 1988

This study optimized the condenser dimension of heat pump system with the heat sources which are solar irradiation and ambient air. At first, the author selected the principal design factors influencing the performance of heat pump system. And the author considered the variation of condenser dimension according to the variation of the selected design factors, that is, ambient air temperature, condenser temperature, degree of superheating, degree of sub-cooling and irradiation. As a result this study, among refrigerants R12, R22 and R500, refrigerant R22 has more heating output than R12 and R500, and the coefficient of performance on this heat pump system is not greatly influenced by the degree of superheating and degree of sub cooling. The ambient air temperature is below $5^{\circ}C$ at balance point and the optimal tube length of condenser dimension is about 3.8 m. Also the author gained the optimal design diagram for the optimization of condenser dimension according to various design factors.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.1-9
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• 2004

The general method which changes sub-cooling of refrigerant is to control the expansion valve in the state of mixing with liquid and gas phase. In this study, the performance of vehicle air conditioning system is to control either changing the expansion valve or adding the sub condenser. Therefore, this research finally is tested in case of the fourth test procedure, the second test was suitable for a valve opening area due to adjusting valve slope in comparison with the other test. The other test except for the second test happened to do liquid back due to the excessively liquified refrigerant into the system. In conclusion, the second test was appeared not to be influenced upon liquid back, and it is to expect positive performance by controlling an expansion valve. Therefore, it will be also useful to research for an increase of compressor efficiency Performance improvement of an air conditioner is to reinforce the suction performance of the evaporator and increase the sub-cooling, which make use of the sub-cooling system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1325-1331
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• 2007

In order to investigate the cooling capacity of an air-conditioner applying a variable capacity compressor and the temperature characteristics on a condenser and an evaporator, the experiment on the operation characteristics of the air-conditioner was performed along a compressor operation ratio and an indoor/outdoor temperatures, under a cooling operation mode. The system characteristics were measured by the psychrometric calorimeter. The cooling capacity increased with decreasing the outdoor temperature and increasing the indoor temperature. Also, it increased with increasing the compressor operation ratio. The temperature of the condenser was more sensitive for the variation of the outdoor temperature and the temperature of the evaporator was more sensitive for the variation of the indoor temperature. The operation characteristics of the cycle used in this present were also analyzed by a pressure-enthalpy chart.

• ETRI Journal
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• v.20 no.3
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• pp.284-300
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• 1998

A new thermosyphon cooling module (TSCM) has designed, fabricated and tested to cool the multi-chip module consists of a cold plate and an integrated condenser. With an allowable temperature rise of $56^{\circ}C$ on the surface of the heater, the cooling module TSCM can handle a heat flux of about 2.7 $W/cm^2$ using R11 as working fluid. The transient characteristics of the cooling module have been proved to be excellent: that is, when a heat load is applied inside of the system, steady state can be achieved within 10 to 15 minutes. It has been found that the length of the vapor channel between the cold plate and the condenser in addition to the ambient and the condenser temperatures affect the system performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.638-646
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• 1985

Water hammering in nuclear or thermal power plant condenser cooling water systems in mathematically modeled and numerically analyzed based on the method of characteristics. Effects of variations of the discharge valve operating condition and the system geometry on the hydraulic transients are investigated for the cases when all or one of four pumps are tripped accidently due to loss of offisite power. Effects of ocean waves and tides on the steady-state and the transient operations are also studied. Water column separation in taken into account whenever necessary by means of a simplified physical model.