• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.79-87
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• 1998

Basic design of a 50USRT(175㎾) triple effect absorption chiller driven by hot gas has been carried out for both parallel and series flow cycles. Parallel flow cycle showed higher COP, however, the temperature in the generator was also higher than that in series flow cycle. Dynamic operation behavior of a parallel flow system at off-design conditions, such as the change in heat transfer medium temperature or the construction change of the system components, has been investigated in detail. It was found that the cooling capacity was seriously decreased by reducing hot gas flow rate and UA-value in the high temperature generator. However, the system COP was improved, because thermal load in the system components was reduced. The COP and the cooling capacity was found to be improved as cooling water temperature decreased or chilled water temperature increased. The optimum ratio of solution distribution could be suggested by considering the COP, the cooling capacity and the highest temperature in the system, which is critical for corrosion.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.10
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• pp.703-709
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• 2007

Much energy is used in occupying stage of the Building Life Cycle. Electric charge is one of the various factors that influence on energy use of residents. This study focused on electric charge and searched that whether electric charge affects residents' behavior of operating air conditioner and their controlled indoor climate. We surveyed three groups for field study ; A group is residents who live in a studio apartment, B group is residents who live in a university dormitory and C group is residents who live in a apartment with their family. The A and C groups are charged for electric as energy consumption they used. And the B group is students who live in a university dormitory and they are not charged for their energy consumption. We measured the time to use the air conditioner for cooling, on/off temperature of air conditioner, and room air temperature for these three groups. The result shows that consideration for electric charge affects to the residents' behavior of operating air conditioner and their acceptable thermal range.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.447-454
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• 2008

The regenerative evaporative cooler(REC) is to cool a stream of air using evaporative cooling effect without an increase in the humidity ratio. In the regenerative evaporative cooler, the air can be cooled down to a temperature lower than its inlet wet-bulb temperature. Besides the cooling performance, for practical application of the regenerative evaporative cooler, the compactness of the system is also a very important factor to be considered. In this respect, three different configurations, i.e., the flat plate type, the corrugated plate type, and the finned channel type are investigated and compared for the most compact configuration. The optimal structure of each configuration is obtained individually to minimize the volume for a given effectiveness within a limit of the pressure drop. Comparing the three optimal structures, the finned channel type is found to give the most compact structure among the considered configurations. The volume of the regenerative cooler can be reduced to 1/8 by adopting the finned channel type as compared to that of the flat plate type.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.925-931
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• 2012

The air-conditioner for railway vehicle should have vibration durability in order to operate normally in vehicle running situation. KS R 9144(vibration test methods for railway vehicle parts) is used to verify the vibration durability. The specifications of compressor, condenser and evaporator for air-conditioner in railway vehicle are standardized, but the shape and structure of pipe lines are not specified. Because the air-conditioner handler produces the pipe line arbitrarily, sometimes the pipe line is broken during the vibration durability test. In this research the cause identification and solution of pipe line breaking problem in during the vibration durability test were studied for air-conditioner of railway vehicle(diesel multiple unit). It was found that the natural frequency of pipe line is related to the pipe line breaking by experiment. A new pipe line shape was introduced by using FEA in order to avoid the resonance. The prototype new pipe line was applied to air-conditioner and the natural frequency was measured by experiment in order to verify the resonance avoidance. The vibration reduction of air-conditioner with new pipe line was reviewed by comparing to the air-conditioner with original one.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.8
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• pp.316-324
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• 2016

This study investigated a compact regenerative evaporative cooler (REC). To achieve practical applications of an REC, it is very important to consider the compactness as well as the cooling performance. Therefore, a prototype of the REC was designed and fabricated to improve the compactness by reducing the length through the insertion of fins in both the dry and wet channels. The REC prototype was tested in terms of performance evaluation under various operating conditions. An analytical model was also developed to analyze the effects of the axial conduction through the solid body of the REC, the wetness of the surface in the wet channel, and the thermal capacity of the evaporation water flow. The model was validated by comparing the results of a simulation with experimental data. The numerical simulation was based on the model to analyze the performance of the REC and to suggest methods to improve the cooling performance of the REC. Finally, the performance of the present REC was compared to that obtained in previous experimental studies. The results showed that the REC prototype in the present study is the most compact and achieves the highest cooling performance.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.621-626
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• 2006

Regenerative evaporative cooling is known as an environment-friendly and energy efficient cooling method. A regenerative evaporative cooler (REC) consisting of dry and wet channels is able to cool down the air stream below the inlet wet-bulb temperature. In the regenerative evaporative cooler, the cooling effect is achieved by redirecting a portion of the air flown out of the dry channel into the wet channel and spraying water onto the redirected air. In this study, a horizontal regenerative cooler is considered. In the horizontal regenerative cooler, the flow direction of evaporating water has a right angle to the flow direction of supply air. This difference was investigated with visualization technique and simplified 2-module performance test was done in a thermo-environment chamber. Optimum design configuration is changed due to the wet channel which are easily fully covered with evaporating water and block the air flow inside the channel. Applying the optimized fin configuration design with the highly wetting surface treatment, a regenerative evaporative cooler was fabricated and tested to Identify the cooling performance improvement and operation characteristics. From the experimental results at the intake condition of $32^{\circ}C$ and 50% RH, the supply temperature was measured to be around $23.4^{\circ}C$. The cooling effectiveness based on the inlet dewpoint temperature was evaluated 73% which is almost close to the design expectation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.874-880
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• 2006

The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

• Journal of Bio-Environment Control
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• v.29 no.3
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• pp.265-276
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• 2020

This study was conducted to provide a basis for raising farm income by increasing the yield and extending the cultivation period by creating an environment where crops can be cultivated normally during high temperatures in summer. The maximum cooling load of the multi-span greenhouse with a floor area of 504 ㎡ was found to be 462,609 W, and keeping the greenhouse under 32℃ without shading the greenhouse at a high temperature, it was necessary to fog spray 471.6 L of water per hour. The automatic fog cooling control device was developed to effectively control the fog device, the flow fan, and the light blocking device constituting the fog cooling system. The fog cooling system showed that the temperature of the greenhouse could be lowered by 6℃ than the outside temperature. The relative humidity of the fog-cooled greenhouse was 40-80% during the day, about 20% higher than that of the control greenhouse, and this increase in relative humidity contributed to the growth of cucumbers. The relative humidity of the fog cooling greenhouse during the day was 40-80%, which was about 20% higher than that of the control greenhouse, and this increase in relative humidity contributed to the growth of cucumbers. The yield of cucumbers in the fog-cooled greenhouse was 1.8 times higher in the single-span greenhouse and two times higher in the multi-span greenhouse compared to the control greenhouse.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.353-362
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• 2019

Thermodynamic analysis of cascade refrigeration systems has attracted considerable research attention. On the other hand, a system evaluation based on thermodynamic analyses of the individual parts, including the evaporator, condenser, intercooler, expansion valve, etc., has received less attention. In this study, performance analysis was conducted on a cascade refrigeration system, which has an individual cooling and refrigeration evaporator, and equips the intercooler and air-cooled condenser in a series in a lower cycle. The thermo-fluid design was then performed on the major components of the system - upper condenser, lower condenser, cooling evaporator, refrigeration evaporator, intercooler, compressor, electronic expansion valve - of 15 kW refrigeration, and 8 kW cooling capacity using R-410A. A series of simulations were conducted on the designed system. The change in outdoor temperature from 26 C to 38 C resulted in the cooling capacity of the lower evaporator remaining approximately the same, whereas it decreased by 9% at the upper evaporator and by 63% at the intercooler. The COP decreased with increasing outdoor temperature. In addition, the COP of the cycle with the intercooler operation was higher that of the cycle without the intercooler operation. Furthermore, the increase in the upper condenser size by two fold increased the upper evaporator by 4%. On the other hand, the lower evaporator capacity remained the same. The COP of the upper cycle increased with increasing upper condenser size, whereas that of the lower cycle remained almost the same. When the size of the lower condenser was increased 2.8 fold, the intercooler capacity increased by 8%, whereas those of upper and the lower evaporator remained approximately the same. Furthermore, the COP of the lower cycle increased with an increase in the lower condenser. On the other hand, the change of the upper condenser was minimal.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2004.11a
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• pp.323-328
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• 2004

This study measured the thermal environment and residents' cooling behavior of the apartments' living rooms in summer in Seoul. The purpose of this study is to find out the present thermal environment of the living rooms and to find out the target figure of passive cooling system. The surveys and measurements took place in six apartments of Seoul for 60days(2004. 7. 3${\sim}$2004. 8. 31). The result were summarized as follows; The thermal environment of apartments' living rooms were almost neutral, and residents felt a little uncomfortable. Residents turned on the air conditioner at $27.31^{\circ}C$ of indoor temperature, and $28.89^{\circ}C$ of SET*. Therefore, cooling critical temperature of the passive cooling system can be figured out from this result.