• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.13 no.3
• /
• pp.1-8
• /
• 2017

Variable refrigerant flow (VRF) systems have recently attracted attention in many countries due to a variety of advantages over conventional system. Especially, the water-cooled VRF heat pump, including geothermal heat pump, is a system that accurately controls the flow rate of refrigerant for the improved efficiency under part load operation. This paper describe the process of generating the cooling and heating energy performance curve coefficients and performance expressions for modeling water cooled VRF system using EnergyPlus. Through this study, the process for generating performance curves can be implemented into EnergyPlus or other comparable building energy analysis tools for the long-term evaluation of heat pump under dynamic conditions.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.14 no.1
• /
• pp.1-7
• /
• 2018

A ground source heat pump system should be equipped with devices to measure the generated heating or cooling heat amount in Korea. Generally, the heat measuring devices have been developed to estimate consumed heat amount in residential or commercial buildings from a central air-conditioning system or a district heating system. In this study, two representive heat measuring devices used for buildings were selected, and the accuracy of them were experimentally estimated at the ground source heat pump operating conditions. The obtained heat amounts from the heat measuring devices were deviated within 4.3% comparing with the precise values calculated from an accredited test facility. Even though the accumulated heat amount values of the heat measuring devices had a small difference comparing with the precise values, the temperatures of heat measuring devices showed greatly different values comparing with the precise temperature. Therefore, it is highly recommended to develop the heat measuring devices which is appropriate for the ground source heat pump systems.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.6 no.2
• /
• pp.15-22
• /
• 2010

The natural refrigerants have used into HVAC equipments because the CFCs and HFCs have some environmental problems like high ODP and GWP. The carbon dioxide has small effect on the environmental problem but also good thermodynamics properties. In this study, the simulation study on the performance and characteristics of a $CO_2$ gascooler and evaporator using a fin-tube and microchannel heat exchanger has been conducted. Besides, the comparison of performance with operating condition was carried out in order to apply to the $CO_2$ heat pump system. As a result, the front sizes of a gascooler and evaporator using a microchannel were decreased by 63% and 58%, respectively, compared to those using a fin-tube. The performance of the fin-tube gascooler and evaporator were more responsive to the variation of operating conditions compared to that of microchannel. The pressure drop of a fin-tube heat exchanger was higher than that of a microchannel one.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.154-158
• /
• 2001

The heat treatment of PVC film containing PVC 65%, DOP(Dioctyl Phthalate) 32% as plasticizer, Ca-Zn stearates and surface agent was peformed under several conditions to study the degradation behavior of PVC sheet. In the case of H$_2$SO$_4$, the dehydrochlorination was ca.100% at 25$0^{\circ}C$ for 3h. The char involving the smaller pores was produced with hydrothermal treatment. The pore size became small with increasing the treatment time and temperature. In the case of treatment with Ca(OH)$_2$, the sizes of pores produced in char were about sever ~ 10${\mu}{\textrm}{m}$ at 2$25^{\circ}C$ for 12h. In the case of H$_2$SO$_4$, the size of pores were about 1${\mu}{\textrm}{m}$ in 5M H$_2$SO$_4$for 12h.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.746-750
• /
• 2001

The heat treatment of PVC film containing PVC 65%, DOP(Dioctyl Phthalate) 32% as plasticizer, Ca-Zn stearates and surface agent was peformed under several conditions to study the degradation behavior of PVC sheet. In the case of H$_2$SO$_4$, the dehydrochlorination was ca.100% at 25$0^{\circ}C$ for 3h. The char involving the smaller pores was produced with hydrothermal treatment. The pore size became small with increasing the treatment time and temperature. In the case of treatment with Ca(OH)$_2$, the sizes of pores produced in char were about sever ~ 10${\mu}{\textrm}{m}$ at 2$25^{\circ}C$ for 12h. In the case of H$_2$SO$_4$, the size of pores were about l${\mu}{\textrm}{m}$ in 5M H$_2$SO$_4$for 12h.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.12 no.4
• /
• pp.15-20
• /
• 2016

Even though the control device of the heating system works well, insufficient water flow rates can degrade control performance and thermal comfort. The water flow rate should be adjusted appropriately to cope with the heating load of each zone. In order to solve these problems, a new balancing concept 'dynamic balancing' was proposed where a balancing valve opening can be automatically modulated according to the heating condition of the room. This study analyzed the effects of dynamic balancing upon indoor thermal environment and energy consumption in a radiant floor heating system through field measurement. Under part-load conditions, the use of a dynamic balancing is a more effective method to reduce energy consumption and to prevent a cavitation. Dynamic balancing is able to help boost the temperature of a room in the start-up period.

• Korean Journal of Materials Research
• /
• v.9 no.7
• /
• pp.675-679
• /
• 1999

An investigation was performed to prepare spherical cobalt powder with about particle size of 400nm from aqueous cobalt hydroxide slurry under hydrothermal reduction conditions using palladium chloride as a catalyst. The reduction kinetics was in good agreement with a surface reaction core model equation. and the activation energy obtained from Arrhenius plots was 55.6 KJ/mol at the temperature range of $145~195^{\circ}C$. Additionally, the study showed that the cobalt reduction rate is proportional to the initial hydrogen pressure with a reaction order of n=0.63. which corresponds to the gas chemisorption reaction type.

• Economic and Environmental Geology
• /
• v.31 no.5
• /
• pp.375-388
• /
• 1998

The purpose of this study is to investigate the ore genesis and occurrence of the Wondong polymetallic mineral deposits. The Pb-Zn, Fe and W-Mo mineralizations are found in skarn zones which formed mainly in or along the fault shear zones with the $N25-40^{\circ}W$ and $N10-50^{\circ}E$ directions, whereas the Cu-Mo mineralization is appeared hydrothermal replacement zone. The skarn minerals consist mainly of garnet and epidote, which were the last alteration phases between pneumatolytic and hydrothermal stages. The mineral paragenesis toward the late stage are as follows: arsenopyrite, scheelite, magnetite, pyrite, pyrrhotite, sphalerite, galena, chalcopyrite and molybdenite. Average ore grades are 0.33 g/t Au, 46.29 g/t Ag, 0.06% Cu, 4.4% Pb, 2.61% Zn and 29.39% Fe in tunnels, and 0.31 % Cu, 0.52% Pb, 6.29% Zn, 29.29% Fe, 0.03% Mo and 0.12% $WO_3$ in drill cores. Fluid inclusion data shows that Type I (liquid-rich), Type II (vapor-rich) and Type III (halite-bearing) inclusions are coexisted and their homogenization temperatures are quite similar. This indicates that boiling conditions have been reached during the mineralization. It is also likely that the ore solutions were evolved through the mixing between magmatic and meteoric waters. Rhyolite and quartz porphyry far the mineralization probably are not responsible of the Wondong polymetallic mineral deposits.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.1 no.2
• /
• pp.1-6
• /
• 2005

Ground water source heat pumps are clean, energy-efficient and environment-friendly systems for cooling and heating. Although the initial cost of ground water source heat pump system is higher than that of air source, it is now widely accepted as an economical system since the installation cost can be returned within a short period of time due to its high efficiency. In a ground water source heat pump system, the variation of the ground water temperature is an important factor that influences the system performance. In this study, variation of the ground water temperature of a single well system is studied experimentally for various operating conditions. When ground water flow exists in the underground, the returned water exchanges heat efficiently with the ground and the temperature of the ground water remains nearly constant. Hence the short circuit problem is minimized. If an active flow of ground water flow exists in the underground, a singe well heat pumps system will be free of short circuit problem and can operate with high performance.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.7 no.2
• /
• pp.37-42
• /
• 2011

Dedicated outdoor air(DOA) system which conditions the outdoor air separately is superior to conventional Cooling + reheating system with respect to energy consumption and indoor comfort. Since the sensible and latent load characteristics of indoor and outdoor are different, it is more efficient to treat them separately. In this study, cycle analysis and on-site performance test of DOA system have been conducted. The study shows that DOA requires 50% less equivalent energy than the conventional system. The on-site performance test of a prototype shows that the coefficient of performance(COP) of the DOA system is 37% higher than the conventional system.