• Journal of Bio-Environment Control
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• v.9 no.1
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• pp.60-64
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• 2000

This study was conducted to investigate effects of cooling methods on the growth and yield of tomato cv. momotaro in the glasshouse for four years from 1996 to 1999. Cooling methods were fan, fan and fogging, fan and shading(temp. control), fan and shading(radiation control), fan and shading (temp. control) with fogging. Fan, Fogging and Shading(temp. control) were operated automatically when air temperature was over 3$0^{\circ}C$. Amount of fogging was 500m1/min/100m$^2$and Droplets in a fog were 50 microns or smaller. Shading(radiation control) was operated automatically when solar radiation was over 500W/m$^2$. The growth and yield were the least in fan and shading(temp. control) method due to lack of light Intensity. Fogging method must be reconsidered for expensive equipment and maintenance expenses. As the matter stands, It is suggested to be the most considerable cooling method to increase ventilation rate with fan or use fan and shading(radiation control).

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.783-787
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• 1996

The rapid growth of air conditioning load has become a main reason of peak load increase in summer. In connection with this, we surveyed the load management projects of utilities world wide and their detailed activities. This study is to develop a remote load control system using computer and radio communications. We finished the field-test of this system on August 1995 in Seoul area. During the field-test, the remote load control of air conditioners was proved to be well-timed. Two control modes, group control and all control, are available for the user to select. The transmission reliability of the load control signal was very good and the functions of system hardware as well as the software were excellent. So we confirmed the applicability of the load control system including the pager communication network. In this paper, detailed information on the system functions and experimental results are described.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.04a
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• pp.69-74
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• 2000

This paper describes an operation strategy of ice storage systems for energy saving during building cooling. In this study, chiller is assumed not having function of part load control. Thus, it is needed to adopt on-off control with the objective function of summed energy consumption for minimum energy consumption. A conventional control strategy compared with the chiller-on-off control is chiller-priority control. in this control chiller operates as its full capacity and ice storage meets the rest of the cooling load.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2000.10b
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• pp.71-74
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• 2000

일반적으로 온실은 저온기에는 보온이나 난방을 하면서 적극 사용하고 있으나 고온기에는 냉방에 소요되는 에너지가 난방에 비해 상대적으로 많이 소요되므로 온실의 활용도가 떨어지게 된다. 자연환기 시스템은 에너지를 사용하지 않거나 최소한으로 줄여 온실내 온도를 최소한 외부와 동일하게 하거나 낮게 하기 위한 장치라고 할 수 있다. 자연환기를 위한 환기창으로 유리온실이나 경질판 온실과 같은 양지붕형 온실에서는 측창으로 3Way방식이나 권취식, 프로젝트방식 등 다양한 환기창을 사용하고 있으나 천창은 주로 온실 길이방향의 연속형 창틀을 랙앤피니언이나 X형 개폐암으로 개폐하는 프로젝트 방식을 많이 사용하고 있다. (중략)

• 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 Bio-Environment Control
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• v.30 no.4
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• pp.335-341
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• 2021

In this study, experiments were conducted to investigate the effects of high- temperature stress on paprika in a semi-closed greenhouse where cooling is available and a normal plastic greenhouse. Paprika grown in a semi-closed greenhouse in which geothermal cooling is provided showed a significantly higher speed of photosynthesis than paprika grown in a 3-layer plastic greenhouse in which there is no cooling system. It suggests that the photosynthesis speed of paprika in a plastic house decreases owing to high temperature stress. Plant height increased by 13cm more in the semi-closed greenhouse, and the size of leaf showed similar growth speed until the 2nd week after transplanting, however, after 3 weeks, the semi-closed greenhouse showed a big difference by 47% compared with the plastic greenhouse. In terms of the fruit count, the semi-closed greenhouse had 10.6 fruits/plant and the plastic greenhouse had 4.6 fruits/plant, indicating that the semi-closed greenhouse had a higher number of fruits by 130% than the plastic greenhouse. The fruit weight also presented a difference between the semi-closed greenhouse and the plastic greenhouse by 46%, which is 566.7g/plant and 387g/plant, respectively. According to the above mentioned results, it was validated that when paprika is cultivated in a semi-closed greenhouse where a cooling system is applied, photosynthesis and growth were better than in the normal plastic greenhouse. Thus, if the hot summer season is overcome by applying the elemental technologies for the cooling system to the normal plastic greenhouse, farm income may increase through improvement in the yield and quality.

• Journal of Bio-Environment Control
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• v.9 no.4
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• pp.201-206
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• 2000

A certain system to overcome high temperature should be introduced for the stable year-round cultivation in greenhouses. There are efficient methods to overcome high temperature such as ventilation system with shading screen, fan and pad system with screen, and fog system with screen. This study was carried out to find a means to determine the capacity of such system. Heat balance equations for each system were established and verified by experimental results. The calculated ventilation rates from heat balance equations showed a good agreement with the measured ones. The evapotranspiration coefficient was the most important parameter affecting the ventilation requirement among input parameter affecting the ventilation requirement among input parameters except weather data. When the evaportanspiration coefficient increased 1%, the ventilation requirement decreased 1.3%. Therefore the data of evapotranspiration coefficient should be accumulated by various experiments, and then design standards and selection guidelines should be provided. The simulation results for same design conditions shown that air exchanges requirement and evaporating water of fan and pad system were 5.1∼7.7% and 6.8∼9.3% larger than those of fog system, respectively.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.322-327
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• 2007

Dedicated outdoor air-conditioning(DOA) system that utilizes pre-cooling and desiccant dehumidification can be superior to conventional cooling and reheating system with respect to energy consumption and indoor thermal comfort. In this work, simulation has been conducted to study various factors that affect the performance of DOA. Dynamic simulation shows the transient variation of temperature and humidity as the on/off control logic is imposed. Exit humidity of process air and flow rate are varied to study the effect on exit temperature of process air, dehumidification quantity, required regeneration temperature and exit humidity of regeneration air. For an outdoor air condition of $28.5^{\circ}C$ temperature, 16 g/kg humidity ratio and 2000 cmh flow rate, the dehumidification efficiency is increased by 4.6% as the flow rate is doubled.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.2
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• pp.173-179
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• 1998

An experimental study was conducted on the effect of compressor capacity control range of heat pump on the seasonal energy efficiency ratio with variation of the maximum and minimum compressor input frequencies. To obtain seasonal energy efficiency ratio, steady state test at the maximum, minimum and intermediate compressor speed and cyclic test at the minimum compressor speed should be conducted. Maximum input frequency was varied to 95Hz, 105Hz, and 115Hz, and the minimum input frequency was varied to 35Hz, 45Hz, and 55Hz. The seasonal energy efficiency ratio increased as the input frequency of the compressor decreased. The maximum input frequency had only slight effects on the SEER.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.31-36
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• 2021

Recently, automobile air conditioning systems have applied an alternative refrigerant that can replace the high GWP refrigerant R134a due to the global warming problem. This study simulated the performance of an automobile climate control system with an internal heat exchanger and TXV. Refrigerant R1234yf was applied as the working fluid. Amesim, a commercial software program, was used to model the main components of the compressor, condenser, TXV, evaporator, and internal heat exchanger. As the outside temperature increased from 30℃ to 40℃, the cooling capacity of the system decreased by 3.1%, and the power consumption of the compressor increased by 17.1%. In addition, The performance characteristics of the refrigeration cycle were simulated by increasing the fin pitch of the condenser from 0.8 mm to 1.4 mm. When the fin pitch was larger than 1.0 mm, the condenser capacity decreased, and the system COP was lowered by 5.9%. When the fin pitch of the condenser was 0.8 mm, which was smaller than 1.0 mm, there was no significant change in the system performance. Hence, the optimal performance was observed at a fin pitch of 1.0 mm.