• Journal of Power System Engineering
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• v.11 no.1
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• pp.51-55
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• 2007

A study on combustion characteristics using emulsified fuel in a diesel engine were performed experimentally. In this paper, the experiments were performed at engine speed 1800rpm, emulsion ratios were 0%, 10%, 20%, and main measured items were specific fuel consumption, cylinder pressure, rate of pressure rise, rate of heat release etc. The obtained conclusions were as follows. 1) Specific fuel consumption increased maximum by 19.8% at low load, but was not affected at full load. 2) Rate of pressure rise and rate of heat release were about the same in the case of 10% and 20% of emulsion ratio. 3) Cylinder Pressure increased 9.6%, rate of pressure rise increased 53.4% in case of emulsion ratio 20% at full load. 4) Rate of heat release increased 72.4% in case of emulsion ratio 20% at full load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.12
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• pp.836-842
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• 2011

It has been shown that the air-conditioning system with slab cooling storage is effective in cutting peak load and utilizing nighttime electric power. The stochastic properties of internal heat generation which has great influence on the cooling load are examined in this paper. Based on the measured cooling load and electric power consumption in an office building with slab cooling storage, stochastic time series models to simulate these random processes are investigated. Furthermore, a calculated result by an optimal control method of thermal analysis taking into account the internal heat is compared with the measured cooling load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.9
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• pp.620-627
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• 2010

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and passes through the opening bored into the footing beam. The air is cooled by the heat exchange with the inside surface of the double slab space in summer, and heated in winter. This system not only reduces sensible heat load of the fresh air by heat exchange with earth but also reduces latent heat load of the fresh air by ad/de-sorption of underground double slab concrete. In this paper, we investigated the correlation between outdoor air temperature and outlet air temperature in the system. In conclusion, from the results of the high correlation we proposed a equation of regression for the outlet air temperature in the system by using linear regression analysis.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.3
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• pp.169-181
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• 2010

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and passes through the opening bored into the footing beam. The air is cooled by the heat exchange with the inside surface of the double slab space in summer, and heated in winter. This system not only reduces sensible heat load of the fresh air by heat exchange with earth but also reduces latent heat load of the fresh air by ad/de-sorption of underground double slab concrete. In this paper, we proposed a simplified presumption method for the prediction of cooling and heating performance in the system. In conclusion the proposed method has been verified by comparing with the calculated value of the numerical analysis model by using nonlinear two-dimension hygroscopic question.

• Plant Journal
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• v.17 no.2
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• pp.42-47
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• 2021

In terms of district heating operation, efficient production and supply of heat by alleviating the peak load at a specific time require an application technology that can solve the inconvenience of the user and the difficulties of the supplier. In this study, a 78 ℃ class PCM heat storage tank suitable among the technologies that can solve these problems was manufactured and applied to the hot water supply facility for apartments in district heating users. As a result of the application of this system, it was confirmed that the supply temperature was constant to the user compared to the existing supply method. In addition, it was confirmed that the reduction of the peak load due to load equalization reduced the heat supply margin of 10% in the existing heat supply facility. And the construction cost of the new heat supply facility and the construction cost of heat users is decreased by 5% and 10%, respectively.

• Plant Journal
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• v.18 no.2
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• pp.32-40
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• 2022

In this study, we investigated the operation data of combined heat and power in accordance with the change of the inlet guide vane with partial load. The partial load 80% could close the inlet guide vane up to 24%, and the exhaust gas temperature could be increased by 52℃. The partial load 90% could close the inlet guide vane up to 12%, and the exhaust gas temperature could be increased by 23℃. At 80% of partial load with the thermal load tracking mode, the output could be increased up to 5.68 MW, the combined cycle efficiency increased by 0.73%, and the combined heat and power efficiency increased by 1.81%. At 90% of the partial load, the output could be increased up to 2.55 MW, the combined cycle efficiency increased by 0.32%, and the combined heat and power efficiency increased by 0.72%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.9
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• pp.455-462
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• 2017

The purpose of this study is to analyze heating and cooling load variation due to envelope retrofits in an old school building. In a previous study, envelope retrofit of an old school building resulted in annual energy consumption reduction. However, cooling energy consumption increased with the envelope retrofit. This is because of high internal heat generation rates in school buildings and internal heat cannot escape through windows or walls when the envelope's thermal performance improves. To clarify this assumption, thermal performance changes due to envelope retrofits were analyzed by simulation. Results revealed indoor temperature and inner window surface temperature increased with high insulation level of windows. Indoor heat loss through windows by conduction, convection and radiation decreased and resulted in an increase of cooling load in an old school building. From results of this study, energy saving impact of envelope retrofits in an old school building may not be significant because of high internal heat gain level in school buildings. In case of replacing windows in school buildings, local climate and internal heat gain level should be considered.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.65-74
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• 1998

The purpose of this paper is to investigate the mount of relief of human solar heat load and thermal comfort in outdoor environment in summer, Six different types of sites, T garden and its neighboring area in Japan, were selected as the experiment sites. The experiments were conducted from 22 to 29 August, 1994 to find the relationship between climatic conditions and human responses, Climatic conditions, subjects's thermal sensation and skin temperature were measured. Radiant heat exchange on the human body was estimated on the basis of the measured air and surface temperature and solar radiation. Thermal index Operative Temperature and New Effective Temperature was modified with the effect of the radiant heat exchange. Human thermal comfort and skin temperature is affected by the solar radiation and the sky factor in an outdoor environment. The effect of tree shade was verified on thermal comfort, The mount of relief of human solar heat load is relation to the existence of shade a solar radiation and the sky factor. The urban garden is one of the effective design element in an urban environmental planning.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1630-1637
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• 2002

A slab-wick heat pipe was fabricated and tested for applications where the condenser temperature is in a range of 80 to 12$0^{\circ}C$. The pipe material was 9.53 mm O.D. copper tube and the working fluids were ethanol and water. The total length of the heat pipe was 1.6 m, in which evaporator section was 1.4 m and the condenser was 0.10 m. The slab was a composite wick structure fabricated with STS316 wire screens. Thermal load was varied for a specified fill charge ratio and inclined angle. The optimum fill charge ratio was identified to be 110% based on a theoretical calculation of the pore space in the slab wick of the heat pipe. The maximum thermal load was 120W for ethanol and the same was 200W for water with the condenser temperature of 8$0^{\circ}C$. The thermal performance of the slab wick heat pipe is analysed in terms of temperature characteristics and thermal resistance against thermal load, tilt angle and fill charge ratio.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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• pp.334-341
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• 2011

In the present study, optimal heat supply algorithm which minimize the heat loss through the distribution pipe line in group energy apartment was developed. Variation of heating load of group energy apartment building in accord with the outdoor air temperature was predicted by the heating load-outdoor temperature correlation. Supply water temperature and mass flow rate were controlled to minimize the heat loss through distribution pipe line. District heating apartment building located in Hwaseong city, which has 1,473 households, was selected as the object building for testing the present heat supply a1gorithm. Compared to the previous heat supply system, 10.4% heat loss reduction can be accomplished by employing the present method.