• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1002-1007
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• 2009

The research are performed to check the characteristics of the ice slurry transport system for the district cooling. The system are installed at the 1st floored building which is as large as the $1204\;m^2$ ($86\;m{\times}14\;m$). Three kinds of heat exchanger are selected, such as, plate, spiral and shell & tube type, to apply to the ice slurry systems. Experiment was done in the two cases. The first case, circulation water flow fixed at the design conditions for the state to change the flow of the supply of ice slurry. The second case, Ice slurry flow fixed at the design conditions for the state to change the flow of circulation water. Both side of Energy balance was calculated. The performance of plate heat exchanger is higher than others and it's enthalpy effectiveness is higher too.

• 한국도로학회논문집
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• 제17권5호
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• pp.1-10
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• 2015

PURPOSES : A finite difference model considering snow melting process on porous asphalt pavement was derived on the basis of heat transfer and mass transfer theories. The derived model can be applied to predict the region where black-ice develops, as well as to predict temperature profile of pavement systems where a de-icing system is installed. In addition, the model can be used to determined the minimum energy required to melt the ice formed on the pavement. METHODS : The snow on the porous asphalt pavement, whose porosity must be considered in thermal analysis, is divided into several layers such as dry snow layer, saturated snow layer, water+pavement surface, pavement surface, and sublayer. The mass balance and heat balance equations are derived to describe conductive, convective, radiative, and latent transfer of heat and mass in each layer. The finite differential method is used to implement the derived equations, boundary conditions, and the testing method to determine the thermal properties are suggested for each layer. RESULTS: The finite differential equations that describe the icing and deicing on pavements are derived, and we have presented them in our work. The framework to develop a temperature-forecasting model is successfully created. CONCLUSIONS : We conclude by successfully creating framework for the finite difference model based on the heat and mass transfer theories. To complete implementation, laboratory tests required to be performed.

• 설비공학논문집
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• 제15권5호
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• pp.360-371
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• 2003

The calculation of each unit cost of productions is very important for evaluating the economical efficiency and deciding the reasonable sale price. In the present, two methods of exergy costing on multiple energy systems are suggested to reduce the complexities of conventional SPECO method and MOPSA method and to improve the calculation efficiency of exergoeconomics. The suggested methods were applied to a gas-turbine cogeneration and the unit costs of the power and the steam energy were calculated as an example. The main points of our methods are the following three. First, one exergetic cost is applied to one cycle or system. Second, the suggested equations are the internal cost balance equation and the production cost balance equation. Third, necessary states in a system are only inlet and exit states of 1ha components producing energy.

• 태양에너지
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• 제9권3호
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• pp.3-12
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• 1989

Semi-greenhouse type solar-dehumidification drying of oak was carried out to investigate the possibility to dry wood using solar energy in Korea. The energy balance equation was set up, considering all the energy requirements, and the solar radiation was calculated to analyze the efficiencies of solar dryer with and without the dehumidifier. The average temperature inside dryer and collector rose up to $52^{\circ}C$ and $70^{\circ}C$, respectively. The average daily total beam, diffuse, and ground-reflected radiations were 7.27MJ, 8.70MJ, and 0.33MJ on the roof and 2.08MJ, 4.84MJ, and 5.37MJ on the south wall collector, respectively. Heat efficiency of solar dryer was 14.04% with dehumidifier and 13.13% without dehumidifier. The energy required to remove 1g of water from wood was 0.0289MJ/g in solar-dehumidification drying and 0.0310 MJ/g in semi-greenhouse type solar drying.

• 설비공학논문집
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• 제20권1호
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• pp.42-48
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• 2008

A numerical simulation has been conducted to investigate the physics of the Ranque-Hilsch vortex tube. Even though currently available turbulent models cannot predict such complex flow accurately, it was expected that the simulation would enlighten underlying physics qualitatively. The balance of energy on a fluid particle moving along some typical streamlines through shear work and heat transfer was investigated to explain the physics of energy separation process. It was found that the heat transfer cancels major part of the energy separation done by shear work. It was also found that the most of energy separation occur near inlet and hot outlet.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1125-1130
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• 2006

An air source heat pump system producing the ice and water storage energy for cooling and heating of building has been proposed. Cycle design and simulation considering energy balance between heating and cooling capacity has been carried out. The roles of the capacity controlled compressor, refrigerant heating device and air preheating are investigated in detail. System control logic for meeting the predetermined heating capacity when the system is operated at cold climate condition is suggested. Some anticipated problems of the proposed system are also described.

• 전기학회논문지
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• 제60권7호
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• pp.1339-1346
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• 2011

This paper is developed to demand management scenario of energy consumption efficiency improvement, electricity generation efficiency improvement, network efficiency improvement, change of distribution ratio, movement of energy source, change of heating system, put of CHP to quantitatively assess to impact on energy use of demand management at the national level. This scenario can be applied Energy System Management model was developed based on Energy Balance Flow. In addition, effect analysis through built demand management scenario was quantitatively evaluated integrated demand management effectiveness of energy cost saving, CO2 emission reduction and energy savings of national level by calculating to primary energy source usage change in terms of integration demand management effect more often than not a single energy source separated electricity, heat and gas.

• 신재생에너지
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• 제6권3호
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• pp.22-29
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• 2010

The concept of Ocean Thermal Energy Conversion (OTEC) is simple and various types of OTEC have been proposed and tried. However the location of OTEC is limited because OTEC requires $20^{\circ}C$ of temperature difference as a minimum, so most of OTEC plants were constructed and experimented in tropical oceans. To solve this we proposed the modified OTEC which uses condenser discharged thermal energy of existing fossil or nuclear power plants. We call this system CTEC (Condenser Thermal Energy Conversion) as this system directly uses $32^{\circ}C$ partially saturated steam in condenser instead of $20{\sim}25^{\circ}C$ surface sea water as heat source. Increased temperature difference can improve thermal efficiency of Rankine cycle, but CTEC should be located near existing plant condenser and the length of cold water pipe between CTEC and deep cold sea water also increase. So friction loss also increases. Calculated result shows the change of efficiency, pumping power, net power and other parameters of modeled 7.9 MW CTEC at given condition. The calculated efficiency of CTEC is little larger than that of typical OTEC as expected. By proper location and optimization, CTEC could be considered another competitive renewable energy system.

• 수산해양기술연구
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• 제53권3호
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• pp.302-307
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• 2017

An electric steam boiler equipped with a condensate recovery system, which stores the condensate generated after using steam in steam washers, steam cookers, steam irons, and steam cleaners in a condensate tank and supplies compressed air to the condensate tank so that the condensate is recovered to the boiler by the pressure of the compressed air, was studied. In the results of this study, the heat energy balance between the quantity of the heat generated by the non-metallic surface heating element and the quantity of the heat absorbed by the water was good in a range of ${\pm}5%$. In addition, the heat transfer rate increased in proportion to the electric power of the surface heating element heater, the waste heat energy was normally recovered by the recovery of the condensate of the steam boiler equipped with the high compression waste heat recovery system, and the recovery rate of the waste heat exhibited 23%.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.236-255
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• 1999

An improved mechanistic model was developed to predict a convective boiling critical heat flux (CHF) in the vertical round tubes with uniform heat fluxes. The CHF formula for subcooled and low quality boiling was derived from the local conservation equations of mass, energy and momentum, together with appropriate constitutive relations. The model is characterized by the momentum balance equation to determine the limiting transverse interchange of mass flux crossing the interface of wall bubbly layer and core by taking account of the convective shear effect due to the frictional drag on the wall-attached bubbles. Comparison between the present model predictions and experimental CHF data from several sources shows good agreement over a wide range of How conditions. The present model shows comparable prediction accuracy with the CHF look-up table of Groeneveld et al. Also the model correctly accounts for the effects of flow variables as well as geometry parameters.