• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.65-74
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• 2008

In this study, dynamic characteristics analysis of AC system is investigated using a cool thermal storage system. A analysing program for cool thermal storage AC system is developed. The performances are studied by several variables and dynamic characteristics. Comparing the result at conventional operation condition with that at the condition using ice storage system, this study showed the effects of the sub cooled degree, superheated degree, efficiency of compressor and evaporating temperature. At the condition using thermal storage system, the thermal storage process was operated during midnight being not needed the cooling of the AC unit through the continuous running of the condenser. The refrigerant was sub-cooled using stored energy after being discharged from the air source condenser during the daytime. The COP was increased owing to the sub-cooling of refrigerant during daytime, thus the power consumption was effectively decreased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.354-364
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• 1994

Experiments have carried out to investigate the effects of parameters, such as mass ratio of R141b-to-water, stirrer speed, brine inlet temperature, brine flowrate, and additives, on the performance of the cool storage system using R141b clathrate. The cool storage system in this experiment was composed of storage tank, refrigerator, and heater. The results show that the mass ratio of R141b-to-water, 1 : 3~1 : 3.5 gives the best performance and the stirring speed has optimum point as 600rpm. At this speed impeller Reynolds number is $1.01{\times}10^5$. The lower the inlet brine temperature and the highter the brine flowrate, the better performance. The addition of metal powder turned out to reduce the degree of supercooling. The supercooling reduction was proportional to the amount of the metal power. However when metal powder was added more than 0.1 wt%, there was no additional supercooling reduction. The surfactants shortened the time consumed for cool storage to the half of no surfactant added case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.3
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• pp.343-353
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• 1997

This paper presents a theoretical model for predicting transient behaviors during storage process of the cool storage system using the R141b clathrate. Introduction of the lumped capacitance method along with a brine reservoir having large thermal capacity yields a set of simplified energy equations. Based on the Arrhenius equation and the known experimental findings, the formation rate of clathrate for which the degree of subcooling is properly accounted is newly developed. An effective nondimensionalization of the model equations facilitates the closure of modeling as well as parametric study. Calculated results for a specific case not only simulate a typical pattern of temperautre variation in the tank successfully, but also agree reasonably well with available data. The effect of each characteristic parameter on the system performance is also investigated. It is revealed that the dominant among relevant parameters are the activation energy of reaction, the degree of subcoling and the initial mass fraction of refrigerant. Finally, the uncertainty associated with modeling of the shaft work variation appears to need further studies.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.681-688
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• 2014

Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.1-9
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• 2002

The purpose of this study is to maintain high efficiency and reasonable use of cool thermal storage systems operated in the domestic building sector. As the result of efficiency test from the five types of operated cool storage systems on the condition that COP ranges are 2.6 to 3.4 during the day time and 2.1 to 3.0 during the night time and it decreased by more than 30% of rated COP given 3.8 to 3.0. The Analysis of cool storage rate shows that only 3 (21.4%) systems out of 15 buildings hold to over 40% capacity for its total capacity. To prevent the decrease in operating efficiency, it should correct the malfunction of 3-way valve and expansion valve and the mistake of control values for schedule program and increase cooling tower capacity. In order to improve piping line, it needs bypass brine line off refrigerator, separation of chilled water line with Ice Slurry system at day and night time and speed control of chilled and warm water pumps. This study does require the more studies on improving difficulty of increasing cooling load with Ice on Coil system, waterproofing with Ice Ball system, COP drop during the night time with Ice Lens, low operating temperature during the day time with Ice Slurry and increasing of Power loss due to hot gas de-icing with Ice Harvest in the future.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.856-857
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• 2007

For the sake of a stable power supply, an electric power company must have power generation facilities that can generate more electricity than the maximum demand of the year. Due to the fact that the maximum electricity demand will also continue to increase, enormous investments are needed annually to build power plants. For that reason, electric power companies are propelling 'Demand Side Management' which improve the form of electrical usage for the customer in a positive way. This paper presents the concept of 'Cool Storage System' which is the most representative program, which lowers the peak demand during the on-peak time periods in a day and creates a base load simultaneously during the night time hours among the DSM programs.

• Solar Energy
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• v.20 no.3
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• pp.11-19
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• 2000

In this study, the basic data which were required for development of LHSS(latent heat storage system) were experimentally obtained. Experiments were carried out under the following conditions. The initial temperatures of P.C.M. which were used by parameter is $5^{\circ}C,\;9^{\circ}C$ and $14^{\circ}C$. The conditions of working fluid are $-6^{\circ}C,\;-4^{\circ}C$, and $65{\ell}$/min.. The pure water of which the freezing point is $0^{\circ}C$ was filled in the system, and the Ethylene glycol(brine) was circulated through the 10 vertical tubes as a secondary fluid in order to cool the P.C.M. down. The inlet temperature of the secondary fluid and the initial temperature of the water were varied to investigate the effects of the important design parameters. The phenomenons of temperature conversion of P.C.M. were appeared for the conductive heat transfer and free convective heat transfer by buoyancy force in this storage unit system. In order to find the effective water circulation path, we obtained P.CM. temperature distributions of 5 parts in the storage tank during freezing process.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.11a
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• pp.167-176
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• 2001

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.879-884
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• 2006

Jinan Poonghyeol in Chonbuk province Is famous for emitting cool air in summer and warm air in winter. Cause for these phenomena is studied by measuring temperature, humidity and air velocity of several locations around Jinan Poonghyeol Temperature variations under the ground are also measured. Analyzing data compiled from July 21, 2005 through May 26, 2006, it is presumed that storage effect of rocks and soil in this area and buoyance effect are the main causes for this mysterious natural air-conditioning phenomena.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.8
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• pp.626-633
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• 2002

The electric power load during the peak time in summer is strongly affected by cooling load, which decreases the preparation ratio of electricity and brings about the failure in the supply of electricity in the electric power system. The ice-storage system and heat pump system etc. are used to settle this problem. In this study, the method of estimating temperature and humidity to forecast the cooling load of ice storage system is suggested. And also the method of forecasting the cooling load using neural network is suggested. For the simulation, the cooling load is calculated using actual temperature and humidity, The forecast of the temperature, humidity and cooling load are simulated. As a result of the simulation, the forecasted data is approached to the actual data.