• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 춘계학술논문발표회 논문집
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• pp.7-10
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• 2008

Heat release characteristics of live fire load are an important parameter for performance oriented fire safety design of a building. While investigations have been carried out on the fire load and its burning behavior in office, residential and commercial buildings and so on, little effort has been paid for the rational treatment of fire load in post office buildings in Japan. In this report, burning behavior of typical combustible objects in post office buildings are studied by measuring heat release rates of plastic palettes with and without postal envelopes or packages and special containers loading numbers of palettes. The test results suggest that dynamic heat release rate is highly dependent on the condition of palettes especially if they load appropriate amount of postal envelopes or not.

• 한국초전도ㆍ저온공학회논문지
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• 제7권3호
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• pp.43-46
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• 2005

A Protomodel Space Infrared Cryogenic System (PSICS) cooled by a stirling cryocooler was designed. The PSICS has an IR sensor inside a cold box which is cooled by a stilting cryocooler with refrigeration capacity of 500mw at 80K in a vacuum vessel. It is important to minimize heat load for reducing background thermal noise. In order to design the cryogenic system of low heat load and to reduce heat load, we did several numerical analyses and tested using boil-off calorimetry with liquid nitrogen to measure the heat leak of the system. In this paper, we present the results obtained by thermal analysis and heat load measurement for designing the PSICS.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3878-3887
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• 2022

For the future energy-mix policy for carbon neutrality, demand for the capability of load-follow operation has emerged in nuclear power plants in order to accommodate the intermittency of renewable energy. The short-term decay heat analysis is also required to evaluate the decay heat level varied by the power level change during the load-follow operation, which is a very important parameter in terms of short-term decay heat removal during a grace time. In this study, the short-term decay heat level for 10 days after the shutdown was evaluated for both seasonal and daily load-follow cases. Additionally, the nuclide-wise contribution to the accumulated decay heat for 10 days was analyzed for further understanding of the short-term decay heat behavior. The result showed that in the seasonal case, the decay heat level was mainly determined by the power level right before the shutdown and the amount of each nuclide was varied with the power variation due to the long variation interval of 90 days. Whereas, in the daily case, the decay heat level was strongly impacted by the average power level during operation and meaningful mass variations for those nuclides were not observed due to the short variation interval of 0.5 days.

• 설비공학논문집
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• 제30권3호
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• pp.130-142
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• 2018

We use heat pumps with thermal storage system to reduce peak usage of electric power during winters and summers. A heat pump stores thermal energy in a thermal storage tank during the night, to meet load requirements during the day. This system stabilizes the supply and demand of electric power; moreover by utilizing the inexpensive midnight electric power, thus making it cost effective. In this study, we propose a system wherein the thermal storage tank and heat pump are modeled using the TRNSYS, whereas the control simulations are performed by (i) conventional control methods (i.e., thermal storage priority method and heat pump priority method); (ii) region control method, which operates at the optimal part load ratio of the heat pump; (iii) load response control method, which minimizes operating cost responding to load; and (iv) dynamic programming method, which runs the system by following the minimum cost path. We observed that the electricity cost using the region control method, load response control approach, and dynamic programing method was lower compared to using conventional control techniques. According to the annual simulation results, the electricity cost utilizing the load response control method is 43% and 4.4% lower than those obtained by the conventional techniques. We can note that the result related to the power cost was similar to that obtained by the dynamic programming method based on the load prediction. We can, therefore, conclude that the load response control method turned out to be more advantageous when compared to the conventional techniques regarding power consumption and electricity costs.

• 한국농공학회논문집
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• 제48권5호
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• pp.51-60
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• 2006

In order to examine the heat transfer characteristic of a soil warming system and effects of soil warming on the greenhouse heating load, control experiments were performed in two greenhouses covered with double polyethylene film. One treated the soil warming with an electric heat wire and the other treated a control. Inside and outside air temperature, soil temperature and heat flux, and heating energy consumption were measured under the set point of heating temperature of $5,\;10,\;15,\;and\;20^{\circ}C$, respectively. Soil temperatures in a soil warming treatment were observed $4.1\;to\;4.9^{\circ}C$ higher than a control. Heating energy consumptions decreased by 14.6 to 30.8% in a soil warming treatment. As the set point of heating temperature became lower, the rate of decrease in the heating energy consumptions increased. The percentage of soil heat flux in total heating load was -49.4 to 24.4% and as the set point of heating temperature became higher, the percentage increased. When the set point of heating temperature was low in a soil warming treatment, the soil heat flux load was minus value and it had an effect on reducing the heating load. Soil heat flux loads showed in proportion to the air temperature difference between the inside and outside of greenhouse but they showed big difference according to the soil warming treatment. So new model for estimation of the soil heat flux load should be introduced. Convective heat transfer coefficients were in proportion to the 1/3 power of temperature difference between the soil surface and the inside air. They were $3.41\;to\;12.42\;W/m^{2}^{\circ}C$ in their temperature difference of $0\;to\;10^{\circ}C$. Radiative heat loss from soil surface in greenhouse was about 66 to 130% of total heating load. To cut the radiation loss by the use of thermal curtains must be able to contribute for the energy saving in greenhouse.

• 한국지열·수열에너지학회논문집
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• 제18권3호
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• pp.19-30
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• 2022

In this study, comparative analysis of energy performance in Taebaek city, a test area, by applying hydrothermal, geothermal source and hybrid heat pump system to office, school and smart farms with different internal heat loads. The conclusion is as follows. In the load characteristics by use of buildings, it was found that office had a large cooling load compared to heating load, school had a large heating load compared to cooling load, and smart farm had only cooling load year-round. Performance analysis of the heat pump system in office shows that the cooling COP of the hydrothermal source is 5.12% and the heating COP is 3.22% lower based on the geothermal source, the cooling COP of the hybrid is 0.41% higher, and the heating COP is the difference in performance appeared sparsely. The performance analysis of the heat pump system in school showed that the cooling COP of the hydrothermal source was 10.44% and the heating COP 3.22% lower based on the geothermal source, and the performance difference between the hybrid cooling and heating COP was insignificant. Heat pump system performance analysis in smart farm only occurred with cooling load. Based on geothermal sources, the cooling COP of the hydrothermal source was 46% and the cooling COP of the hybrid was 19.65%, respectively.

• 한국산업융합학회 논문집
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• 제7권4호
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• pp.331-340
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• 2004

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 used a model for evaluation of fresh air latent heat load reduction by hygroscopic of air to earth exchange system taking into account coupled heat and moisture transfer of underground double floor space. In conclusion it shows the validity of the proposed method for a design tool and the quantitative effect of the system.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.50-59
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• 1996

The computer simulation program that calculates the transient heat load transferred to a passenger vehicle has been developed. Method for modeling mathematically various kinds of the heat load was presented and the derived equations were solved numerically. To find out the accuracy of the simulation program, the correlation of experimental and analytical results was demonstrated. By using this program, the typical characteristics about temperature distribution and instantaneous or of vehicle body color, material of glass, air-conditioning capacity, driving direction, and speed. Under a steady-state condition, the ratios of the heat load, resulting form vehicle body, glass, and interior part, were 35%, 29%, and 36%, respectively.

• 한국전산유체공학회지
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• 제19권4호
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• pp.1-7
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• 2014

A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under a sinusoidal heat load was conducted. It was found that the time constant is not affected by the maximum heating magnitude of the sinusoidal heat load. However, the time constant increases with low duration of the sinusoidal heating period and low Reynolds number. Moreover, there is a threshold where a heater temperature do not reach to time constant at low thermal diffusivity, low flow rate, and low pulse duration of the sinusoidal heating. The time constant should be considered for transient convective heat transfer under transient sinusoidal heat load in a micro heat sink.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.170.1-170.1
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• 2010

Performance of water-to-air heat pump using raw water has been analyzed under part load heating operation in March, 2010. The water source heat pump of 30 RT was installed for 24 hours cooling and heating ventilation, and the gravity inflow water from Daechung dam is used as the heat source. The daily averaged water and air temperatures are $5.7^{\circ}C$ and $9.9^{\circ}C$ respectively, and the heat pump is operated under part load condition for 7.5 hours in 24 hours. The daily averaged heat pump COP calculated with heat transferred from the brine water is 2.49 and the monthly averaged COP is 2.25 in March. Based on the database of the California Energy Commission, the monthly averaged COPs of air source heat pumps installed in U.S.A. are 1.97 in March and 2.03 in April. Therefore it is confirmed again that the performance of the heat pump using raw water is better than that of air source heat pumps.