• Journal of the Korean Solar Energy Society
• /
• v.27 no.4
• /
• pp.43-49
• /
• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.

• Solar Energy
• /
• v.9 no.3
• /
• pp.37-43
• /
• 1989

This paper dealt with thermal storage efficiency due to difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank [$0.5m{\times}0.5m{\times}1.0m$] and the temperature of water flowing into the tank, flow rate of water flowing into the tank and shape of porous manifold which water flow into the tank through. As results of experiments; (1) When the flow rate was constant and the diameter of porous section decreased by 8mm, 6mm, and 4mm, the thermal storage efficiency increased. (2) When the diameter of porous section was constant and the difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank and the temperature of water flowing into the tank increased by -30, -20, -10, 5, 10, 15 ($^{\circ}C$), the thermal storage efficiency increased. (3) When the($T_{\infty}-Ti$) was constant and the flow rate decreased by 0.8, 0.4, 0.25(LPM), the thermal storage efficiency increased. (4) When the shape of porous section was rigid, the thermal storage efficiency was the most effective, and with establishing flexible porous section or mesh, the effective thermal storage efficiency was obtained.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.178-183
• /
• 2008

The purpose of this study is to compare the effect on the thermal stratification under various aspect ratios in the solar storage tank using FLUENT. Numerical calculations of three designs with different aspect ratio were carried out to show the behaviour of stratification in a solar storage tank. The calculation results show that the thermal stratification of the 2.5:1 aspect ratio solar storage tank can be 6.22% higher then that of the 1.5:1 aspect ratio solar storage tank and 2.68% higher then that of the 2:1 aspect ratio solar storage tank.

• Journal of Biosystems Engineering
• /
• v.15 no.2
• /
• pp.123-133
• /
• 1990

Thermal performance of a solar heating plastic greenhouse designed for a hydroponic system was studied. The system was constructed with the air-water heat exchanger and thermal storage tank that were combined with hydroponic water beds. Experiments were carried out to investigate the daily average heat stored and released in thermal storage tank, average solar energy collection efficiency, average coefficient of performance, average oil reduction factor of thermal storage system, and the heat transfer coefficient during the nighttime in plastic greenhouse. The results obtained in the present study are summarized as follows. 1. Daily average heat stored in thermal storage tank and released from the thermal storage tank was 1,259 and $797KJ/m^2$ day, respectively. 2. The average solar energy collection efficiency of thermal storage tank was 0.125 during the experiment period. And the average coefficient of performance of thermal storage system in plastic greenhouse was 3.6. 3. The average oil reduction factor of thermal storage system and the heat transfer coefficient during the nighttime in plastic greenhouse were found to be 0.52 and $4.3W/m^2\;hr\;^{\circ}C$, respectively.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.11a
• /
• pp.188-192
• /
• 2006

This study is conducted to improve efficiency of thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from solar or the others heat sources. However, it has difficulties in storing heat with uniform temperature through the entire tank with respect to vertical direction. This kind of maldistribution of the supplied heat to the storage tank effects on the system performance. In this study is focused on utilization of the thermal stratification to improve thermal comfort for people in the house. To enhance temperature stratification of the tank, a distributor was designed and Installed in the middle of the tank. The distributor is supplies hottest water to the top side of the tank which is very close to inlet of the supply line to the heating load. The hottest water that is accumulated on top side of the tank is firstly supplied to the load with higher temperature. Reminder water takes a little time to warming up until desired supply temperature reached. This kind alternating selection of the supply temperature is improve thermal comfort with moderated system performance.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.266-269
• /
• 2009

The Purpose of this study was thermal performance of solar hot water and space heating thermal storage tank. The combi storage tank was designed Tank in Tank type. The tank volume for space heating was 700 $\ell $ and tank volume for hot water was 150 $\ell $. Tank in Tank type storage tank was to replace heat exchange to hot water tank. The result showed that the Heating value was 67.25MJ and domestic hot water value was 51.93MJ. Supply to the hot water volume was 521 $\ell $ more than about 3 times as that of the hot water tank volume.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.5
• /
• pp.82-88
• /
• 2013

There are the stirring test and drain test in the daily performance test to determine the thermal performance of a domestic solar hot water system. The drain test is a test that measures the discharge heating rate while drain the hot water from the top of the storage tank and supply the city water to the bottom of the tank. From the perspective of the user, this drain test is more effective than the stirring test. In this study, the thermal performance were compared through the drain test for a passive type and an active type domestic solar hot water systems consisting of the same storage tank and collectors. At this point, a passive type was used the horizontal storage tanks, and an active type was used vertical storage tank. In the drain test, when the hot water drained up to the reference hot water temperature, an active type which have vertical storage tank represents excellent daily performance than a passive type which have horizontal storage tank regardless of weather conditions. The reason for this is because the vertical storage tank is advantageous to thermal stratification in the tank. After the drain test, the residual heat for the horizontal storage tank was much more than the vertical storage tank, but in the next day the amount of discharged heat were less than the those of vertical storage tank neither. Thus, the solar water heating system which have horizontal storage tank should be adopted preheating control method rather than separate using control method when connected with auxiliary heat source device.

• Solar Energy
• /
• v.19 no.4
• /
• pp.11-20
• /
• 1999

The study on ice thermal storage system is to improve total system performance and increase the economical efficiency in actual air-conditioning facilities. To obtain the high charging and discharging efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therefore the process flow must be piston flow in the cylindrical type. In the influence of the inlet port type, the inflowing water in the distributor type diffuses through the whole storage tank more than in the slot type. In case of the flow process in the ice storage tank, the upward flow type in the charging process and the downward flow type in the discharging process make the stratification well, thereby the loss of energy wored be smaller. The influence of the inlet temperature difference and the change of the inlet flow rate is intensive when the temperature difference is larger, the flow rate is smaller in case of charging and the results are opposite in case of discharging with the reason that the good coduction condition. The total effeciency of the ice thermal storge system is 73% on condition that the porosity in the thermal storage tank is 0.55. This result shows that cylinderical ice storage tank has better storage capacity than rectangular type in case of the same porosity.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.2
• /
• pp.11-17
• /
• 2002

This paper is concerned with the development of a new method for making, separating ice and storage floated ice by installing an evaporation plate at under-water within a storage tank. In a conventional harvest-type ice storage system, a tank saves ice by separating an ice from an installed evaporation plate, which is located above an ice storage tank as an ice storage system. Developed new harvest-type method shows good heat transfer efficiency than a convectional method. It is because the evaporation panel is directly contacted with water in a storage tank. Also, at a conventional system a circulating pump, a circulating water distributor and a piping are installed, however these components are not necessary in a new method. In this study ice storage systems are experimentally investigated to study the charge and discharge of thermal energy. The results show the applicable possibility and performance enhancement of a new type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.4
• /
• pp.330-335
• /
• 2012

A characteristic behavior of the thermal storage tank for varying thermal load in heat pump water heater was studied. The control method was suggested and applied. By measuring the temperature within the storage tank, the heat pump was ON/OFF controlled. The appropriate measuring position and the size of heat exchanger gives the minimized power consumption of heat pump. As the length of heat exchanger increases, the temperature measuring position goes down of the storage tank and the power consumption increases.