• Transactions of the Korean hydrogen and new energy society
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• v.15 no.4
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• pp.341-347
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• 2004

An experimental study has been carried out on cooling perfonnance of a thennoelectric module. This problem is of particular interest in the design of the refrigeration systems using thermoelectric module, such as cosmetic refrigerator, wine cellar and air cooler. The effect of the input voltage and the hot side temperature on the cooling performance is studied in detail. The $\Delta$T, temperature difference between cold side and hot side surface of thermoelectric module, is described in terms of the input voltage and the hot side temperature. It is found that the cooling capacity can be improved by increasing the input voltage and by reducing the heat from the hot side of the thermoelectric module. However, COP is decreased with an increase in the input voltage, since power consumption is also increased. Thus, optimum input voltage can be selected based on cooling capacity and COP.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.1
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• pp.1-6
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• 2015

This study presents analysis of the experimental data meeting conditions of several applications in real time. The results of this experimental study are as follows: Respectively in cooling and heating performance, a refrigerant charge tank can take automatic control of variation of the refrigerant quantity by controling pressure and temperature of system and outlet water temperature. The COP shows 3.5 in cooling operation and 3.2 in heating operation. The refrigerant quantity increases 0.69 kJ/h. When the outdoor temperature decreases $1^{\circ}C$, Therefore if the temperature become lower from $25^{\circ}C$ to $-16^{\circ}C$, the refrigerant quantity increases about 9.5%. Compared to the normal state experiment results, the COP in automatic control of the refrigerant quantity rises roughly 10%.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.404-409
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• 2005

In this paper a 2-stage $CO_2$ cycle was simulated to predict the performance characteristics with operating parameters. The simulation results showed similar tendency compared to the measured system pressure, capacity, COP etc. System characteristics were analyzed with the variations of outdoor temperature and EEV opening. In the simulation, the highest COP was 2.7 at 30-30 Hz and it decreased as compressor frequency increased. Besides, system COP can be increased by optimizing EEV opening.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.2
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• pp.94-102
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• 2015

A hydroscopic polymer is used as the adsorbent in an adsorption refrigeration system. A pair of plate-type heat exchangers, thinly coated with the polymer, is simulated using a two-dimensional transient model to predict performance of the system. It is predicted that the system would yield 0.57 kW SCP and 0.47 COP at $80^{\circ}C$ heating and $30^{\circ}C$ cooling temperatures. In comparison with a conventional silica gel-water system, the COP is comparable but SCP is about three times larger. The slow mass diffusion rate of the polymer should be improved for better performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.649-656
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• 2010

The aim of this study is to investigate the influence of the secondary fluid flow rate through GLHX on a GSHP system with vertical single U-tube type GLHXs. The COP of a GSHP system with large flow rate was lower than it with small flow rate due to large power consumption of ground loop circulating pump. It is suggested that the heat pump unit with high COP and low flow rate through the GLHX have to be selected in order to enhance the performance of the system and reduce the length of GLHX.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.9-15
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• 2008

In this paper, we suggest PI control with a predictive controller to progress both energy saving and coefficient of performance(COP) in a variable speed refrigeration system. The capacity and superheat are controlled simultaneously and independently by an inverter and an electronic expansion valve respectively for saving energy and improving COP in the system. The refrigeration system has long dead time in superheat inherently. The dead time makes the system difficult to achieve the satisfactory quick control response, especially superheat control response. In order to solve this problem, we designed a predictive controller based on PI control to progress superheat control performance. The control performance was investigated through some experiments to verify the effectiveness of the predictive controller.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.455-461
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• 2001

Domestic ice making companies make effort to obtain products and neglect to introduce low cost product improvements with energy savings. The work presented here is an implementation of ice making method to improve both energy efficiency and productivity. In this present investigation, several ice making cycles are proposed for higher efficiency in the system. COP(Coefficient of Performance), ice making time and electric energy consumption are evaluated and compared with the conventional system. Results shows that COP is improved with more efficient use of time for ice making and electric consumption. Therefore, this can offer an opportunity for more efficient use of energy and higher productivity in ice making.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.505-513
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• 2001

A revised VX cycle using ammonia/water as the working fluid is a cycle which is suitable to produce cooling utilizing low temperature hat sources. The cycle was analyzed numerically to investigate the effects of the design and operating conditions on the performance. It was shown that both COP and cooling capacity were significantly influenced by the performance of he rectifier. Insufficient UA of the rectifier reduced both ammonia mass fraction and mass flow rate of the vapor entering the condenser, which produced cooling effect in the evaporator. As the temperature and the mass flow rate of the heat source increased, both COP and exergetic efficiency decreased due to the irreversibilities produced in heat exchangers, but cooling capacity did not vary much. Cooling capacity increased significantly as the coolant temperature decreased, although COP and exergetic efficiency remained nearly constant.

• Review of KIISC
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• v.22 no.3
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• pp.13-18
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• 2012

인터넷은 사회 경제적 상호작용을 위한 기본적인 인프라가 되어 사람들에게 많은 혜택을 주는 반면 여러 가지 다양한 위험들을 가져왔다. 또한 인터넷을 사용하는 어린이의 수가 증가하고, 그 연령이 더 어려지면서 어린이를 온라인상에서 보호하는 것은 중요한 이슈가 되고 있다. 본 논문에서는 온라인상에서 미성년자를 보호하기 위한 기술적인 대처 방안에 대한 분석을 수행하였다. COP의 다양한 기술들을 활용하여 어린이들을 위험으로부터 벗어나게 할 수 있으며(filtering technologies), 특정한 사이트에 어린이를 접근하지 못하게 하고(age or identity verification systems), 인터넷 상에 어린이들을 안전하게 할 수 있는 안전지대(walled garden)를 만들 수 있다. 이러한 기술적인 대처 방안들은 여러 기술들을 조합하여 사용해야 그 효과성을 높일 수 있으며, 특히 미성년자들의 개인정보 보안을 고려하여 균형적으로 사용해야 한다. 이외에도 COP에서 기술적인 대처방안의 발전적인 개발을 위해서는 보안기술 사이에 정보를 공유할 수 있는 표준이 개발되어야 하며, 보호 기술의 장점 및 기능을 파악할 수 있는 표준 성능 인자의 개발이 필요하다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.116-124
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• 2007

An adsorption chiller is expected to have high energy-efficiency in utilizing the waste heat exhausted from a process. The objective of this paper is to investigate the performance of silica gel-water adsorption chiller from the cycle simulation and to provide a guideline for design of the adsorption chiller. The effect of cycle time, inlet temperature and water flow rate on the cooling capacity and COP is quantified during the cycle operation. It is found that the performance of adsorption chiller is more sensitive to the change of inlet water temperature rather than the water flow rate. It is concluded that the COP is 0.57 in the standard conditions(hot water $80^{\circ}C$, cooling water $30^{\circ}C$, chilled water inlet temperatures $14^{\circ}C$ and cycle time 420sec).