• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.5
• /
• pp.467-472
• /
• 2013

A raw-water source heat pump equipped with a thermal storage tank was dynamically simulated by TRNSYS, and the results were verified by using the data from a heat pump installed in the Seongnam water treatment facility. The average coefficient of performance (COP) of the raw-water source heat pump based on simulation was 4.97 and 3.17 in the cooling and heating season, respectively. When the volume of the thermal storage tank was changed from 5 to $20m^3$, the highest COP was found at a size of $10m^3$. Considering the regional locations of raw-water source heat pumps at Seoul, Incheon, Gangneung, and Gwangju, Seoul showed the lowest electric power consumption in the cooling season and the highest in the heating season. When a comparison of the performance between the present system and that of a water-air heat pump was conducted, the present system showed lower electric power consumption by 25% than that of a water-air heat pump.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.12 no.1
• /
• pp.17-22
• /
• 2016

It is very important to obtain a out-of season production in horticultural greenhouses corresponding with higher crop prices. A ground source heat pump system has been highly spotlighed as an energy efficient heating system for the greenhouse. This paper investigated the operating cost of the ground source heat pump system with the variation of generating temperature and designing methods for heating system of the greenhouse. Even though the COP of the ground source heat pump system decreased with an increment of generating temperature in heating mode, the operating cost could be reduced. By adopting the high temperature heat pump system and heat storage tank, it could be achieved to save energy and reduce the operating time of auxiliary oil heating system for producing good plant-growth in the greenhouse.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.10
• /
• pp.678-686
• /
• 2011

Simulation study on the operating characteristics in the solar hybrid R744 heat pump system for residential applications was carried out with heat pump operating temperature, outdoor temperature and solar radiation. As a result, collector operating time is decreased by 1.5 hours due to the increase of water temperature in the heat storage tank when the heat pump operating temperature rises. Heat pump operating time is reduced by 19.4% owing to the high temperature of a heat storage tank. Besides, indoor heating time is decreased from 10.3 to 5.5 hours as the indoor temperature increases from $3^{\circ}C$ to $11^{\circ}C$. In addition to, when the solar radiation rises from 10 to 20 MJ/$m^2$, the maximum outlet temperature of a solar collector is increased from $65^{\circ}C$ to $71^{\circ}C$.

• Solar Energy
• /
• v.19 no.1
• /
• pp.19-27
• /
• 1999

In this study, basic design data which were required for development of highly efficient ice storage system with low temperature latent heat were experimentally obtained. The ice storage system considered in this study was the one that has been widely used in the developed country and called the ice-on-coil type. Using the system, the ice storage performance for various design parameters which were the flow direction and the inlet temperature of the secondary fluid was tested. In addition, the clockwise variation of the heat transfer characteristics of the PCM in the ice storage tank were investigated. During the melting processes in the ice storage tank with several vertical tubes, decrease of the solid-liquid interface area, which was the heat transfer area, between the floating ice and the water made the decreasing rate of IPF less. Also, the total melting energy for the upward flow of the secondary fluid was higher than that for the downward flow during the melting process, but this trend did not appear if the initial temperature of the PCM was $4^{\circ}C$. The average ice recovery efficiency for the upward flow of the secondary fluid was higher than that for the downward flow.

• Solar Energy
• /
• v.18 no.1
• /
• pp.99-109
• /
• 1998

The study on ice thermal storage system is to improve total system performance in actual air-conditioning facilities. To attain the high efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therfore the process flow must be piston flow in thermal storage tank. Ice packing factor is better on condition that the inflowing temperature is low, the flow direction in the thermal storage is upward and the cylindericalthermal storage type is used. This result shows that the cylinderical ice storage tank has better storage capacity than the rectangular type in case of the same porocity.

• Solar Energy
• /
• v.19 no.4
• /
• pp.33-43
• /
• 1999

The study on ice thermal storage system is to improve total system performance and increase the economical efficiency in actual all-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. With the relation of the aspect ratio(H/D) in the storage tank, the stratification is formed better as inlet flow rate is smaller. If the inlet and the outlet port are settled at the upside and downside of the storage tank, higher storage rate could be obtainable. In case that the flow directions inside the thermal storage tank are the upward flow in charging and the downward in discharging, thermal stratification is improved because the thermocline thickness is maitained thin and the degree of stratification increases respectively. In the charging process, in case of inlet flow rate the thermal stratification has a tendency to be improved with the lower flow rate and smaller temperature gradient in case of inlet temperature, the large temperature difference between inflowing water and storage water are influenced from the thermal conduction. The effect of the reference temperature difference is seen differently in comparison with the former study for chilled and hot water. In the discharging process, the thermal stratification is improved by the effect of the thermal stratification of the charging process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.9
• /
• pp.647-653
• /
• 2007

In dynamic ice storage system(DISS), ice slurry is formed not only from solution freezing by mechanical removing parts but also supercooled solution. However, in order to perform continuous ice formation in the system without mechanical moving parts, supercooled aqueous solution should be formed stable through cooling heat exchanger and be dissolved uniformly in storage tank. In previous study, the time of ice slurry increased as the pressure of the cooling heat exchanger(PHX) increased. In this study, a cooling experiment of an ethylene glycol 7mass% solution was performed with various inlet temperature of the PHX, which has constant brine inlet temperature of $-7^{\circ}C$. The temperature in the storage tank maintained to freezing point of the solution. At results, the time of ice slurry formation increased as the supercooling degree decreased and the cooling rate increased.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.5
• /
• pp.525-533
• /
• 2022

In this study, in order to numerically analyze the heat flow characteristics in the valve according to the opening rate for the solenoid valve for hydrogen supply applied to the hydrogen storage tank, flow characteristics were comparatively analyzed. Through the analysis of pressure and temperature distributions within the valve according to the high-pressure supply condition of 70 MPa or more, the heat flow characteristics in the valve, inlet and outlet passage according to the opening rate of the valve were identified. As a result a sudden change in the fluid behavior appears in the neck region of the valve, and it is understood that the flow separation caused by the flow path shape of the expanded tube has a dominant influence on the flow characteristics. And, it was confirmed that the shape of the valve seat is a factor significantly affecting the improvement of flow rate and differential pressure performance.

• Solar Energy
• /
• v.15 no.3
• /
• pp.15-27
• /
• 1995

This study presents experimental and numerical results of the temperature characteristics, the heat transfer phenomema, and the heat storage quantity during the heat storage process with sodium phyrophosphate decahydrate($Na_4P_2O_7{\cdot}10H_2O$)-Phase Change Material(PCM) in a latent heat storage tank(cubic type). It was proved that heat transfer by conduction was dominant because PCM($Na_4P_2O_7{\cdot}10H_2O$) during heating processes was gel phase, not liquid phase The gap ratio(rate of air content) of PCM became smaller, the thermal capacity of PCM became larger, therefore the temperature distribution of PCM slowly increased than that of large gap ratio. There was maximum 15% difference between measured temperatures and calculated temperatures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.6
• /
• pp.503-511
• /
• 2002

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a degree of stratification in the storage tank, and a useful rate of hot water was analysed with respect to the variables dominating a extraction process. Experimental results show that the degree of stratification and useful rate of hot water are all high in a low flow rate in case of using modified distributor I (MDI) as the outlet port type.