• Journal of the Korean Society of Safety
• /
• v.20 no.2 s.70
• /
• pp.98-104
• /
• 2005

Saw dust concrete f3r finding out insulation characteristic was tested using test plate $30cm{\times}30cm{\times}5cm$. basically, molds f3r the test of compressive, tensile, normal without sawdust, $0.05\%,\;0.1\%,\;0.2\%,\; 0.4\%,\;0.6\%,\;0.8\%,\;1.0\%,\;1.2\%,\;1.4\%,\;1.6\%,\;1.5\%,\;2.0\%$, mixing proportion. heat conductivity of the saw dust concrete mixed with the above proportion was taken in this study. Thermal conduction of normal concrete depends on mixing proportion strength aggregate character, water content. all these items are specified here in fables. $1.8\%\~2.0\%$ saw-dust mising concrete shows as the faction as normal insulation material has its function. and the higher saw-dust mixing rate becomes, the thermal conduction becomes the less Then, the conclusions are that saw-dust using concrete has better insulation function than normal concrete.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.5
• /
• pp.233-240
• /
• 2015

This paper discusses compressors operating number control strategy using cooperative logic to cope with variable partial load for high efficiency of a centrifugal water chiller. The cooperative logic is composed of a speed-up and speed-down controller, enabling smooth operation of compressors and equivalent distribution of thermal load in each compressor. This centrifugal water chiller design can be operated with high efficiency without incurring excessive energy waste and large transient phenomena at partial load states. Simulations in MATLAB and experiments in a real chiller system were conducted and verified the high efficiency control of a centrifugal water chiller achieved by the suggested strategy.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.1
• /
• pp.15-22
• /
• 2011

It is a great interest to convert more energy in the heat source into the power and to improve the efficiency of power generating processes. Since the efficiency of power generating processes becomes poorer as the temperature of the source decreases, to use an ammonia-water mixture instead of water as working fluid is a possible way to improve the efficiency of the system. In this work performance of ammonia-water regenerative Rankine cycle is investigated for the purpose of extracting maximum power from low-temperature waste heat in the form of sensible energy. Special attention is paid to the effect of system parameters such as mass fraction of ammonia and turbine inlet pressure on the characteristics of system. Results show that the power output increases with the mass fraction of ammonia in the mixture, however workable range of the mass fraction becomes narrower as turbine inlet pressure increases and is able to reach 16.5kW per unit mass flow rate of source air at $180^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.5
• /
• pp.647-655
• /
• 2021

The IMO (International Maritime Organization) is discussing the improvement of energy ef iciency of ships in order to reduce greenhouse gas emissions from ships. Currently, by applying an ORC power generation system using waste heat generated from ships, high energy conversion efficiency can be expected from ships. This technology uses an organic medium based on Freon or hydrocarbons as the working fluid, which evaporates at a lower temperature range than water. Through this, it is possible to generate steam (gas) and generate power at a low and low temperature relatively. In this study, the analysis of heat flow between the refrigerant and waste heat in the ORC power generation system, which is an organic Rankine cycle, is analyzed using 3D simulation techniques to determine the temperature change, velocity change, pressure change, and mass change of the fluid flowing of the WHRU (Waste Heat Recovery Unit) inside and the outside the structure. The purpose of this study is to analyze how the mass change affects the structure, and this study analyzed the heat transfer of the heat exchanger from the refrigerant and the exhaust gas of the ship's main engine in the ORC power generation system using this technique.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.1
• /
• pp.81-86
• /
• 2013

Exhaust gas from a small portable electric generator is simply exhausted to the surroundings because the capacity and quality of the waste heat of this gas is generally not sufficient to recover and utilize. We have proposed a seawater distiller utilizing the thermal energy of waste gas from an electric generator. The distiller recovers heat from the waste gas by means of a heat pipe and uses it effectively through a multiple-effect diffusion-type structure. We constructed an experimental apparatus with a vertical single-effect still having a 4-stroke 50 cc generator engine and found that the experimental results for distillate productivity show good agreement with the theoretical predictions. The results show that the distiller can recover 52 W of waste heat from the gas at $171^{\circ}C$, and ~85% of the recovered heat can be utilized for distillation to produce 70 g/h of fresh water. This is equivalent to a productivity of 500 g/h in the case of a 10-effect still. Therefore, the proposed distiller should be useful in remote areas where electricity and water grids are inadequate.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.1 no.1
• /
• pp.1-8
• /
• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having the effect of groundwater movement, understanding of thermohydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated by using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.001 are shaped circular, and the center is moved less than 5 m to the direction of groundwater flow in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of east boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• Nuclear Engineering and Technology
• /
• v.52 no.1
• /
• pp.19-26
• /
• 2020

Small nuclear reactor features higher power capacity, longer operation life than conventional power sources. It could be an ideal alternative of existing power source applied for special equipment for terrestrial or underwater missions. In this paper, a 25kWe heat pipe cooled reactor power source applied for multiple use is preliminary designed. Based on the design, a thermal-hydraulic analysis code for heat pipe cooled reactor is developed to analyze steady and transient performance of the designed nuclear reactor. For reactor design, UN fuel with 65% enrichment and potassium heat pipes are adopted in the reactor core. Tungsten and LiH are adopted as radiation shield on both sides of the reactor core. The reactor is controlled by 6 control drums with B₄C neutron absorbers. Thermoelectric generator (TEG) converts fission heat into electricity. Cooling water removes waste heat out of the reactor. The thermal-hydraulic characteristics of heat pipes are simulated using thermal resistance network method. Thermal parameters of steady and transient conditions, such as the temperature distribution of every key components are obtained. Then the postulated reactor accidents for heat pipe cooled reactor, including power variation, single heat pipe failure and cooling channel blockage, are analyzed and evaluated. Results show that all the designed parameters satisfy the safety requirements. This work could provide reference to the design and application of the heat pipe cooled nuclear power source.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.3
• /
• pp.175-182
• /
• 2009

The spent cationic exchange resins and anionic exchange resins were separated from mixed spent exchange resins by a fluidized bed gravimetric separator. The separated resins were identified by an elemental analysis and thermogravimetric analysis. The each test sample was prepared by diluting the slurry made by wet ball milling the cationic exchange resins and the anionic exchange resins separated as a spherical granular form for 24 hours. The resulting test samples showed a slurry form of less than $75{\mu}m$ of particle size and 25,000ppm of $COD_{cr}$. The decomposition conditions of each test samples from a thermal power plant were obtained with a lab-scale(reactor volume : 220mL) supercritical water oxidation(SCWO) facility. Then pilot plant(reactor volume : 24 L) tests were performed with the test samples from a thermal power plant and a nuclear power plant successively. Based on the optimal decomposition conditions and the operation experiences by lab-scale facility and the pilot plant, a commercial plant(capacity : 150kg/h) can be installed in a nuclear power plant was designed.

• Resources Recycling
• /
• v.9 no.3
• /
• pp.13-21
• /
• 2000

This study describes to analyze the heat transfer characteristics of waste solvent recovery system using a double pipe heat exchanger heating solvent by the hot oil. The solvent recovery system consists of the feeding pump, the double pipe heat exchanger, the vacuum spray chamber, and the condenser. A double pipe heat exchanger consists of the first section to conduct the heating of solvent to the thermal saturated point and the second section to evaporate the saturated solvent. The heat transfer area for vaporization of water, benzene and alkylbenzene was predicted by the heat balance modelling and experimentally measured from the temperature distribution as a function of solvent flow rate and heating temperature. The required heat transfer area for vaporization was increased with increasing solvent flow rates and with decreasing heating temperatures due to decreased quantity of transferred heat per the unit area. Theoretical modelling of the heat transfer area for solvents vaporization in the pipe showed good agreement with experimental results. Results showed to be suitable for the waste solvent recovery using a double pipe heat exchanger.

• Nuclear Engineering and Technology
• /
• v.51 no.6
• /
• pp.1540-1553
• /
• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.