• Progress in Superconductivity and Cryogenics
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• v.26 no.1
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• pp.20-24
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• 2024

Over the past four years, as the COVID-19 pandemic has struck the world, cold chain of COVID-19 vaccination has become a hot topic. In order to overcome the pandemic situation, it is necessary to establish a cold chain that maintains a low-temperature environment below approximately 203K (-70℃), which is the appropriate storage temperature for vaccines, from vaccine suppliers to local hospitals. Usually, cryocoolers are used to maintain low temperatures, but it is difficult for small-scale local distribution to have cryocooler due to budget and power supply issues. Accordingly, in this paper, a cryogenic TSU (Thermal storage unit) system for vaccination cold chain is designed that can maintain low temperatures below -70℃C for a long time without using a cryocooler. The performance of the TSU system according to the energy storage material for using as TSU is experimentally evaluated. In the experiments, four types of cold storage materials were used: 20% DMSO aqueous solution, 30% DMSO aqueous solution, paraffin wax, and tofu. Prior to the experiment, the specific heat of the cold storage materials at low temperature were measured. Through this, the thermal diffusivity of the materials was calculated, and paraffin wax had the lowest value. As a result of the TSU system's low-temperature maintenance test, paraffin wax showed the best low-temperature maintenance performance. And it recorded a low-temperature maintenance time that was about 24% longer than other materials. As a result of analyzing the temperature trend by location within the TSU system, it was observed that heat intrusion from the outside was not well transmitted to the low temperature area due to the low thermal conductivity of paraffin wax. Therefore, in the TSU system for vaccine storage, it was experimentally verified that the lower the thermal diffusivity of the cold storage material, the better low temperature maintenance performance.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.570-574
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• 2010

The main function of conventional insulation materials is only to block the heat transfer and reduce heat loss from the building. On the other hand, thermal storage materials can work as an energy saver by absorbing or emitting heat within a specific temperature range. Thermal storage materials for building can maintain a constant temperature by effectively regulating the cycle of indoor temperature. As a result, we can enhance the performance of a cooling and heating system efficiently. In this study, phase change materials (PCMs) were added as thermal storage materials into gypsum boards which are extensively used for building material and we found out the thermal environmental characteristics. In addition, we checked out some problems when applying the thermal storage materials to buildings. Finally, This study set out to examine the degree of environmental-friendly characteristics of thermal storage building materials by analyzing the amount of TVOC and HCHO contents with the possibility of pollutants emission.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.3-8
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• 2006

The heat pump system is attractive alternatives to conventional heating and cooling systems owing to their higher energy utilization efficiency. The thermal loads of commercial and institutional buildings are generally cooling-dominated. In this study have been developed ice storage type heat pump system for cooling and heating by heat pipe. This system was practiced performance test on evaluation criteria for heat storage systems. Accomplished the actual proof examination and looked into the performance of the system. In this study, measurement and analysis of ice storage type heat pump system for cooling and heating by heat pipe. The heat pump unit COP appears 3.05 for cooling and 4.20 for heating. As a result, the method to energy saving and to using a substitute energy actively that is heat pump cooling & heating system is expected by heat pipe. Thermal storage capacity appears $19.5RTH/m^3$ for cooling.

• Journal of Soil and Groundwater Environment
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• v.26 no.3
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• pp.14-24
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• 2021

Aquifer thermal energy storage (ATES) system uses groundwater thermal energy for cooling and heating of buildings, and it is also often utilized to provide warm water to crops and plants for the purpose of enhancing agricultural yields. This study investigated the potential influences of a ATES system on the geochemical properties of groundwater by simulating the variation of hydrochemistry and saturation index of groundwater during ATES operation. The test bed was installed at an agricultural field, which is mainly composed of an groundwater-rich alluvial plain. The simulation results showed no significant precipitation of mineral phases such as manganese-iron oxide, carbonate and sulfate around the ATES test bed, as well as no debasement of other important water quality parameters. The implementation of ATES system in the study area was appropriate and effective for utilizing the thermal energy of groundwater for agricultural use.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.7 no.1
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• pp.13-19
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• 1978

An experiment has been performed of find a temperature distribution of the circulating fluid in a packed bed thermal storage system when the inlet fluid temperature is constant. The thermal storage system is a specific-heat type in which the circulating fluid, hot air, exchanges heat directly with the heat storage materials, glass balls, in a heat storage bin. An empirical equation which includes two dimensionless variables $t^*\;and\;T_f^*$, is obtained. Also, heat storage efficiency and heat storage capacity are calculated from this equation, The heat transfer coefficient calculated by the suggested equation was compared with the value determined by the existing empirical equation.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3581-3590
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• 2023

High-temperature design evaluations were conducted on Type 316L stainless steel piping for a 700 ℃ large-capacity thermal energy storage verification test loop (TESET) under construction at KAERI. The hot leg piping with sodium coolant at 700 ℃ connects the main components of the loop heater, hot storage tank, and air-to-sodium heat exchanger. Currently, the design rules of ASME B31.1 and RCC-MRx provide design procedures for high-temperature piping in the creep range for Type 316L stainless steel. However, the design material properties around 700 ℃ are not available in those rules. Therefore, a number of material tests, including creep tests at various temperatures, were conducted to determine the insufficient material properties and relevant design coefficients so that high-temperature design on the 700 ℃ piping may be possible. It was shown that Type 316L stainless steel can be used in a 700 ℃ high-temperature piping system of Generation IV reactor systems or a renewable energy systems, such as thermal energy storage systems, for a limited operation time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.1
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• pp.87-94
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• 2006

In this paper, we investigated a feasibility of applying highest and lowest temperatures of the next day forecasted from a meteorological observatory to operation of an air-conditioning system with thermal storage. First we investigated specific characteristics of the time series of forecasted temperatures and errors in Osaka from 1994 to 1996. Since the forecast error is not always small, it might be difficult to use the forecasted data without correction for the sizing and the control of the thermal storage system. On the other hand, the autocorrelation functions of the forecast errors decrease relatively slowly during high summer season when cooling thermal storage is required. Since the values of the autocorrelation function; for one day are larger than 0.4, not small, the forecast errors can be predicted by proper statistical analysis. Thus, the forecasted values of the highest temperatures for the next day were improved by using the stochastic time series models.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.218-223
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• 2009

Cost related to building equipment accounts for about 85% of the life cycle cost of buildings. Therefore proper selection of air-conditioning system is important for reducing the overall cost of buildings. In this study, large capacity ice thermal storage and absorption chiller-heater for air-conditioning a building with a floor area of $9,900\;m^2$ are compared economically. For easy input and analysis, an Ms Excel VBA program has been developed. To consider all the factors of initial and operation costs effectively, an annual equal payment method is proposed. Under the assumptions made in this study, overall cost of an absorption chiller-heater is less than that of an ice thermal storage, but this is not absolute and different outcome may result if different assumptions are made. This study is useful for those who are interested in choosing an economical air-conditioning system for large-size buildings with simple calculations.

• Journal of the Korean Solar Energy Society
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• v.35 no.3
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• pp.73-79
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• 2015

In this study, a thermal storage performance and characteristics of daily operation were investigated when the air and the liquid were heated simultaneously by a hybrid solar air-water heater that can make hot water as well as heated air. The hybrid solar air-water heater is kind of a flat plate solar collector that can make hot water and heated air by installing air channel beneath absorber plate of traditional flat plate solar collector for hot water. As a result of daily operation, maximum water temperature reached in a thermal storage was shown $44^{\circ}C$ on 73kg/h of air mass flow rate and about $40^{\circ}C$ on 176kg/h of air mass flow rate. Thus, the necessity of heating water in thermal storage by operating only liquid side was confirmed when the temperature of liquid in thermal storage is lower than we need. In case of efficiency investigated on daily operation, the thermal efficiency of the liquid side was decreased with increment of the inlet liquid temperature and decrement of the solar radiation, but efficiency of the air side was increased with increment of inlet liquid temperature difference as the traditional solar air heater. Total thermal efficiency of the collector was shown from 65.85% to 78.23% and it was decreased with increment of the inlet liquid temperature and decrement of solar radiation same as the traditional system.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.241-259
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• 2013

A packed bed thermal energy storage (TES) consisting of solid storage medium of rock or concrete through which the heat transfer fluid is circulated is considered as an attractive alternative for high temperature sensible heat storage, because of the economical viability and chemical stability of storage medium and the simplicity of operation. This study introduces the technologies of packed bed thermal energy storage, and presents a numerical model to analyze the thermal energy balance and the performance efficiency of the storage system. In this model, one dimensional transient heat transfer problem in the storage tank is solved using finite difference method, and temperature distribution in a storage tank and thermal energy loss from the tank wall can be calculated during the repeated thermal charging and discharging modes. In this study, a high temperature thermal energy storage connected with AA-CAES (advanced adiabatic compressed air energy storage) was modeled and analyzed for the temperature and the energy balance in the storage tank. Rock cavern type TES and above-ground type TES were both simulated and their results were compared in terms of the discharging efficiency and heat loss ratio.