• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.34-41
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• 2004

The chemical heat pump based on the Dehydration/Hydration process with a MgO/$H_2O$ system has been researched. The reactor bed could be expected to store the heat around 200∼37$0^{\circ}C$ by the dehydration reaction and to release the heat around 100∼16$0^{\circ}C$ by the hydration reaction under the heat amplification mode operation. The heat output rate of the heat pump system was evaluated using the experimentally determined parameters. The results show that 6∼50 W/kg of heat output and 0.5∼0.8 of heat recovery ratio are attainable. The heat pump will be applicable for a load leveling in a co-generation system by chemical storage of surplus heat at low heat demand and by supplying heat in the peak load period.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.197.1-197.1
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• 2010

This study was carried out to evaluate the operating performances of the evaporation desalination system with solar energy. This system was designed to use evacuated solar collector as the heat source, supplying the required heat energy and photovoltaic power as the electric source, supplying required power to pumps in the desalination system. The 5kW photovoltaic power generation system to make the electricity, the single-stage fresh water generator with plate heat exchanger, and remote control and monitoring system. Solar desalination system was designed and installed in Jeju-island, Korea in 2006, after about 4 years of operation, usability and stability of solar desalination system was guaranteed. The system comprises of the desalination unit which was designed to have daily fresh water capacity of $2m^3$, a $120m^2$ evacuated tubular solar collector to supply the heat, a $6m^3$ heat storage tank, and a 5.2kW photovoltaic power generation to supply the electricity to hydraulic pumps for the heat medium fluids. On a clear day, average daily solar irradiance in Jeju-island was measured to be $500W/m^2$ and the daily fresh water yield showed to be more than 500 liters under this condition. After around three years of a long term operation of the system from January 2007 to August 2009, average daily freshwater yield was analyzed to be around $330{\ell}$. The relationship equation between solar irradiance and freshwater yield was found to be y=1.1806x - 107.89.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.866-871
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• 2006

Recently according to the fashion of well-being, the case study of under floor heating system type for residential space is increasing. Specially double slab floor system can make several roles as reducing the acoustic noises and also supplying fresh air through the gap. So in present study floor heating performance was examined with various location of the space in the case of floor supply air and ceiling supply air. In both cases return air went out through ceiling opening. As one of the result is that when using the heat pipe type floor heating system the temperature difference between supply and return water was $15.2^{\circ}C$, but in case of commercial type floor heating system the temperature difference was $5.3^{\circ}C$ when the supply water temperature was $50^{\circ}C$.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.161-167
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• 2006

The purpose of this study is to find the optimal conditions of PCM slurry manufacturing equipment for saving the marketing cost and keeping the original quality of products. In addition, the characteristics of the movable container for shipping or distributing products is analysed. The major results are as follows. 1. PCM thermal storage system is designed with the conditions of temperature($-5{\sim}10^{\circ}C$), cold chain time(30 minutes), and one time usage(50 liter). This system includes tank, freezer, circulating pump, cycle type heat exchanger, swelling tank, equipment of supplying PCM supplying unit includes cold tank, cycle type heat exchanger, suction unit and control equipments, etc. 2. After ability test of PCM thermal storage system, it shows that the required freezing time of PCM thermal storage system is less than one of the previous system. The reason is that churn (top and bottom) and compulsion circulation are occurred simultaneously and unit cooler type method is better than chiller type method. 3. By the experiment of transportation latent heat container, it is decided that the best container is $K_1$ with latent heat temperature($0{\sim}5^{\circ}C$) and density(0.15%). However, for $K_l\;and\;K_2$, it is necessary more studies on latent heat thermal conditions and conditions of making method.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.513-520
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• 2018

Since Paris Climate Change Conference in 2015, many policies to reduce the emission of greenhouse gas have been accelerating, which are mainly related to renewable energy resources and micro-grid. Presently, the technology development and demonstration projects are mostly focused on diversifying the power resources by adding wind turbine, photo-voltaic and battery storage system in the island-type small micro-grid. It is expected that the large-scaled micro-grid projects based on the regional district and town/complex city, e.g. the block type micro-grid project in Daegu national industrial complex will proceed in the near future. In this case, the economic cost or the carbon emission can be optimized by the efficient operation of energy mix and the appropriate construction of electric and heat supplying facilities such as cogeneration, renewable energy resources, BESS, thermal storage and the existing heat and electricity supplying networks. However, when planning a large residential town or city, the concrete plan of the energy infrastructure has not been established until the construction plan stage and provided by the individual energy suppliers of water, heat, electricity and gas. So, it is difficult to build the efficient energy portfolio considering the characteristics of town or city. This paper introduces an energy mix optimization(EMO) method to determine the optimal capacity of thermal and electric resources which can be applied in the design stage of the real large-scaled residential town or city, and examines the feasibility of the proposed method by applying the real heat and electricity demand data of large-scale residential towns with thousands of households and by comparing the result of HOMER simulation developed by National Renewable Energy Laboratory(NREL).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.10 no.2
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• pp.98-108
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• 2000

Controlling the over-exposure of welding fumes is not an easy problem because neither general nor local exhaust ventilation systems could be successfully applied. A jet air supplying welding mask was development to reduce the exposure level of welding fumes. The jet airs tream pushes the welding fumes away from the breathing zone by using the frictional characteristic of jet. Laboratory experiments were conducted to optimize the efficiency of controlling welding fumes. Thereafter, its performance was tested in a laboratory and an industrial field. The efficiencies of reducing the welding fume exposure were about 90% and 80% in a laboratory and an industrial field, respectively. Additionally, it resulted in elimination of heat inside the mask and enhancement of clear visuality.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.26-31
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• 2012

A numerical study has been carried out to investigate the heat and mass transfer of an oil pumping system with a variable shape of the housing using the CFD method. Especially, the electric motor and the pump combined together, accomplishes a research about the oil supplying system. In this study, the temperature and velocity distribution of the oil pumping system by varying the flow rate of supplying oil have been investigated. The temperature changes with each five conditions(flow rate of supply oil : 2, 4, 8, 12, and 16 liter/min) have also been studied. The numerical results show that the exhaust temperature decreases as the flow rate of the supplying oil increases. It also reveals that the temperatures change differently with the housing shape.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.241-246
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• 2007

The present paper dealt with an experimental study of boiling heat transfer characteristics of $CO_2$. Heat transfer coefficients of the refrigerant flow inside horizontal smooth microchannel were obtained with inner tube diameter of 0.3mm and length of 300mm. The direct electric heating method was applied for supplying the heat uniformly to the refrigerant. The experiments were conducted with $CO_2$ purity of 99.99%, at saturation temperature of $10^{\circ}C$, mass flux ranges of $300{\sim}900\;kg/m^2s$, and heat flux ranges of $15{\sim}45\;kW/m^2$. While heat transfer coefficient increased with the increase of heat flux in the low quality region, the heat transfer coefficient decreased with the increase of quality in the high quality region. The heat transfer coefficients were compared with seven existing correlations with the Gungor-Winterton's(1986) correlation gave the best prediction. A new corelation to predict the two-phase flow heat transfer coefficient was developed based on the Chen(1966) correlation. The new correlation predicted the experimental data well with a mean deviation of 9.69% and average deviation of -3.03%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.11
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• pp.600-605
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• 2013

Ground source heat pump systems (GSHP) can achieve higher performance of the system, by supplying more efficient heat source to the heat pump, than the conventional air-source heat pump system. But building clients and designers have hesitated to use GSHP systems, due to expensive initial cost, and uncertain economic feasibility. In order to reduce the initial cost, many researches have focused on the energy-pile system, using the structure of the building as a heat exchanger. Even though several experimental studies for the energy-pile system have been conducted, there was not enough data of quantitative evaluation with economic analysis and comprehensive analysis for the energy-pile. In this study, a prediction method has been developed for the energy pile system with barrette pile, using the ground heat transfer model and ground heat exchanger model. Moreover, a feasibility study for the energy pile system with barrette pile was conducted, by performance analysis and LCC assessment. As a result, it was found that the heat exchange rate of a barrette pile was 2.55 kW, and the payback period using LCC analysis was 8.8 years.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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• pp.477-485
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• 2006

A study on frost prevention of fin-tube heat exchanger is experimently performed by spreading antifreezing solution on heat exchanger surface. It is desirable that the antifreezing solution spreads completely on the surface forming thin liquid film to prevent frost nucleation and crystal growth and to reduce the thermal resistance across the liquid film. A small amount of antifreezing solution falls in drops on heat exchanger surface using two types of supplying devices, and a porous layer coating technique is adopted to enhance the wettedness of antifreezing solution on the surface. It is observed that the antifreezing solution liquid film prevents fin-tube heat exchanger from frosting, and heat transfer performance does not degrade through the frosting tests. The concentration of supplied antifreezing solution can be determined by heat transfer analysis of the first row of heat exchanger to avoid antifreezing solution freezing due to dilution by moisture absorption.