• 설비공학논문집
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• 제13권11호
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• pp.1097-1105
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• 2001

The purpose of this study is to investigate the propriety of TMA clathrate as a cold storage medium. Particularly, this is to examine the extent of subcooling improvement when the additives are added to the TMA clathrate, because water used cold storage material has low phase change temperature and subcooling. This study has been analysed and compared with TMA 30 wt% clathrate how phase change temperature, subcooling and specific heat in the various concentrations are changed. This results view to be improved phase change temperature and subcooling of TMA 30 wt% as a cold storage medium, when it had some additive. Additional1y, it is found that the additive must be controlled under available solution limit and study for new additive must be lasted to know its effect.

• 설비공학논문집
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• 제12권2호
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• pp.189-199
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• 2000

This paper investigates the thermodynamic performance of latent heat thermal energy storage system using two phase change materials(2-PCM system). The thermodynamic merit of using 2-PCM is clear in terms of exergetic efficiency, which is substantially higher than that of 1-PCM system. Optimum phase change temperature to maximize the exergetic efficiency exists for each case. The heat transfer area ratio of high temperature storage unit, X, becomes another important parameter for 2-PCM system if the phase change temperatures of given materials are different from those of optimum conditions. It is a good approximation for X$_{opt}$ to be 0.5 when optimum phase change temperatures are used. Otherwise X$_{opt}$ is determined differently as a function of given phase change temperatures.res.

• 설비공학논문집
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• 제23권12호
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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.

• 설비공학논문집
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• 제13권2호
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• pp.80-87
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• 2001

Microencapsulated PCM particles are mixed with distilled water and utilized to evaluate its characteristics and performance as a thermal storage medium transporting heat. For the present study, tetradecane(C$_14H_30, T_m=5.5^{\circ}C$) is capsulated in the core with the melamine of its surface. The size of particles is well-controlled under 10${\mu}{\textrm}{m}$ in the way of in-situ polymerization with melamine-formaldehyde resin. For the experiment, the concentrations of slurries are prepared for 20wt%, 30wt%, and 40wt%. The results are compared with those of water and 100% tetradecane oil. The pure water and tetradecane start solidifying within 20 minutes after introducing cooling water into the thermal storage tank whose tank whose flow rates are varied by 125cc/min, 250cc/min, and 500cc/min. However, MicroPCM slurries are required relatively longer period of time for their phase change than pure phase change materials. That is, the entrained MicroPCM particles control its heat transfer in terms of natural convection and conducting to them.

• 한국태양에너지학회 논문집
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• 제35권5호
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• pp.21-29
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• 2015

In this study, the performance of hybrid solar air-water heater when the heated air was used as inlet air was investigated during air and liquid were heated simultaneously. Temperature difference between inlet air and ambient was set as $0^{\circ}C$, $13^{\circ}C$ and $22^{\circ}C$ and it was maintained during the daily operation. As a result, thermal efficiency of liquid heating was increased when the inlet air temperature was increased and heat gain of the water in heat storage tank was also increased with increment of temperature difference between inlet air and ambient temperature. On the contrary to this, the decrement of air heating efficiency and total efficiency of collector was confirmed with increment of inlet air temperature and it is considered that heat gain of liquid side is lower than heat loss of air side that occurring by using heated air as inlet air of collector. So, from these results, maximum temperature that the liquid in heat storage tank can reach was expected to increase if the return air or any heated air was used as inlet air. But air and total efficiency of hybrid solar air-water is decreased, so using outdoor air as inlet air is considered as better way on perspective of using of solar thermal energy by hybrid solar collector. However, it is hard to conclude that using outdoor air is better than heated air on the perspective of energy saving of building because the performance of heat storage performance was increased even air and total thermal efficiency was decreased, so the necessity of more profound consideration about these result in further research was confirmed for putting the hybrid solar air-water heater to practical use.

• 설비공학논문집
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• 제16권11호
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• pp.1028-1034
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• 2004

Recently, the ice storage system using ice slurry has been used increasingly since it has been introduced where the rapid cooling load change is required. Because it overcomes a decrease of the melting performance and an increase of the thermal resistance on the ice layer in static ice thermal storage system. This study is performed to understand the effects of transporting ice slurry through horizontal, vertical and inclined tubes ($30^{\circ},\;45^{\circ}$). It used propylene glycol-water solution and ice particles (diameter of about 2 mm) in this experiment. The experiments were carried out under various conditions, with concentration of water solution ranging from 0 to $20wt\%$, and velocity of water solution at the entry ranging from 1.5 to 2.5 m/s. The results were as follows: Regarding the angle of inclined tube, the highest pressure loss was measured for vertical tube and the pressure loss for $45^{\circ},\;30^{\circ}$, horizontal straight tubes were lower successively. The lowest pressure loss in these tubes was measured at velocity of $2.0{\sim}2.5m/s$ and concentration of $10wt\%$. The outlet IPF was likewise stable in these ranges.

• Fisheries and Aquatic Sciences
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• 제25권4호
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• pp.231-242
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• 2022

Effect of different concentrations of hypotaurine (HTU) on melanosis and quality of shrimps during 10 d storage in ice were studied. During refrigeration, the total plate count and total volatile basic nitrogen of shrimps treated with 20 g/L HTU were the lowest, and the hardness and microstructure were the best. Moreover, the score of melanoses, pH and total bile acid of shrimps treated with 20 g/L HTU were also low. Sensory evaluation showed that HTU treatment could make the shelf life of shrimps 3-4 days longer compared with the control. Based on the above physical and chemical indexes, 20 g/L HTU showed great potential as a safe inhibitor in the treatment of shrimps' melanosis.

• 설비공학논문집
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• 제17권4호
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• pp.341-346
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• 2005

The simplification of solar thermal systems reduces the possibility of operating trouble and lowers the cost of the initial investment and maintenance. This also leads to increased competitiveness in the energy market. We proposed a spiral-jacketed storage tank that functions both as a heat exchanger and expansion tank, which removes the secondary piping and markedly simplifies the entire system. The new storage tank was designed and manufactured to maintain the same performance as the conventional system and the exiting system was remodelled by adopting the newly proposed storage tank. This experiment was conducted under real conditions over a period of several months. The retrofitted system with the spiral-jacketed storage tank showed good performance that is on a similar level as the previous system having a typical storage tank and heat exchanger.

• 설비공학논문집
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• 제12권11호
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• pp.982-993
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• 2000

This paper describes an optimal control scheduling of an encapsulated ice storage system with a chiller of nominal chiller 34RT(103,200kcal/hr) and an ice storage tank of 170RT-hrs(514,080 kcal). The optimization technique used in the study is dynamic programing. The objective function is summed cost during a day including charge and discharge periods. Control strategies being used commercially are chiller priority and storage priority control. In chiller priority control, the chiller is allowed to run at full capacity during the day, subject to limitations of the building load, and the ice is only melted when and if the load exceeds the chillers full capacity. In contrast to chiller priority control, the aim in storage priority control is to melt as much as ice as possible during the day time period. The system simulation calculates the operation costs for the three control strategies in the condition of the same cooling load and the same ice storage system. The simulation period is a day, assuming that initially the tank is stored fully and the cooling load is perfectly predicted for the scheduling. Also Final state of the tank is to be charged fully.

• 설비공학논문집
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• 제5권3호
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• pp.187-197
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• 1993

In this study, the numerical analysis and experiments of the hot water storage using the thermal stratification techniques were carried out. The CPU time for a typical run of the the thermal stratification up to 900 seconds took one week for a $81{\times}31$ mesh size and 10 days for a $118{\times}31$ mesh size, respectively, for a cylindrical shape of the storage. In the initial stage, the numerical results were in favorable agreement with the experimental results, but it showed that the temperature gradients in the storage decreased gradually with time. It was also found that the increase of ${\delta}t$ decreased the convergent speed due to the intensive fluctuation of the velocity field in every iteration. The increase of numbers of grids is projected to forecast a more accurate result, but it made the computing time longer and woul slow down convergence. At the experiments of the flow visualization, it was confirmed that the thermal stratification was apparently built up due to the installation of diffuser at the lower part of the storage. Thus, the thermal performance of the storage could be improved by installing the diffusers at the inlet and outlet.