• Journal of Welding and Joining
• /
• v.31 no.4
• /
• pp.62-66
• /
• 2013

Overlay welding is carried out to improve the corrosion resistance, wear resistance and heat resistance on the surface of the chemical plant and steelmaking plant structures. In overlay welding, control of the bead size and the temperature distribution of weldment are particularly important because that is directly connected to the improvement of quality and productivity. The aim of this study is to model the welding heat source that is very useful to analyze the bead size and temperature distribution of weldment. To find the welding heat source model, numerical analyses are performed by using FE software MSC-marc.

• Proceedings of the SAREK Conference
• /
• 2008.11a
• /
• pp.21-26
• /
• 2008

Recently, small and medium-sized buildings have employed a multi-heat pump. The major benefits of the multi-heat pump over a conventional system are that it is easier system to maintain along with a diversification of facility use, and high comfortability. The performance of multi-heat pump systems can be enhanced by using geothermal energy instead of air source energy. This paper describes the multi-heat pumps applied in an ground source heat pump system for an actual building. The performance of a ground source multi-heat pump installed in the field was investigated in cooling mode. The maximum COP of the systems with single U-tube and double tube ground loop heat exchangers were 6.6 and 6.0, respectively. It is suggested that the new algorithms to control the flow rate of secondary fluid for ground loop heat exchanger have to be developed in order to enhance the performance of the system.

• Restorative Dentistry and Endodontics
• /
• v.32 no.6
• /
• pp.491-497
• /
• 2007

The purpose of this study was to compare apical sealing ability of continuous wave canal filling technique according to various heat source plugging depths. Eighty one extracted human premolars with straight root were cleaned and shaped to size 35 using .06 taper rotary NiTi file. After cleansing and shaping, the teeth were divided into 5 groups following the heat source probing depths from the apex; 3, 4, 5, 6 and 7 mm. All specimens were filled using E&Q plus with #35/.06 tapered gutta-percha cone. The positive control teeth were not filled. All teeth were coated with nail varnish except the apical 1 mm around the apical foramen. Negative control teeth were completely sealed include the apical foramen. All specimens were immersed in 1% methylene blue solution for 72 hours. Then the specimens were sectioned horizontally at 1, 2 and 3 mm from the root apex. Each sectioned surface was photographed using a digital camera attached to the stereomicroscope at $12.5{\times}2.5$ fold magnification. All points at 1, 2 and 3 mm were summed as final score of one specimen. Statistical analysis of the collected data was performed. Under the condition of this study. there was no significant difference between the heat source plugging depths of 3, 4, 5, 6 and 7 mm in apical sealing ability. All of apical heat source plugging depth from 3 to 7 mm including Buchanan's protocol -from 5 to 7 mm- seems to be acceptable in clinical application.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.53 no.6
• /
• pp.145-152
• /
• 2011

In order to heat greenhouse nearby river channel, riverbank filtration water source heat pump was developed for getting plenty of heat flux from geothermal energy. Recharging well, thermal storage tank with separating insulation plate and filtering tank for eliminating iron, manganese were mainly developed for making the coefficient of performance (COP) of heat pump higher. Heating system using riverbank filtration water source heat pump was installed at a paprika greenhouse in the Jinju region where a single fold of vinyl cover and 2 layers of horizontal thermal curtain were installed as a part of temperature keeping and heat insulation with a greenhouse area of 3,185 $m^2$. 320,000 kcal/h was supplied for performing a site application tests. A greenhouse heating test was performed from Feb. 1, 2011 to Apr. 30, 2011. As the result of that, COPh of the heat pump was measured in the range of 4.0~4.5, while COPS of the system was represented as 2.9~3.3. COP measured of the heat pump was very good and well responded to indoor heating temperature of the environment control system of a greenhouse.

• Journal of the Korean Solar Energy Society
• /
• v.27 no.1
• /
• pp.47-54
• /
• 2007

Interests on renewable energy are increased due to oil price and environmental problems aroused from the fossil energy usage. In this study, performances of a solar assisted hybrid heat pump system are analyzed by experimental method. The developed system could runs at two types of operating mode. When the storage temperature is higher than the set temperature, the stored hot water in storage tank is supplied to the load directly. On the other hand, when the storage temperature lower than the set temperature, the water inside of the storage tank is used as heat source of the heat pump. In this study, the system control temperature for the alternation of the operating mode is set to $40^{\circ}C$ of the storage tank outlet. As results, it is founded that the COP of the developed heat pump system shows between 3.0 and 3.5. It is resonable performance for the heating system with a renewable energy as secondary heat source. The solar collect used in this study could supplies heat to the storage tank at over 400 W/m2 solar intensity. If the irradiation is lower than the 400 W/m2, the circulation pump stored and it could not supply heat to the storage tank. It is found that the difference temperature between the outlet of the storage tank and collector is $3^{\circ}C$. Even though, the extended study should be conducted to get a optimum performance of the developed system with various operating condition and control strategies.

• Journal of Mechanical Science and Technology
• /
• v.18 no.4
• /
• pp.681-688
• /
• 2004

For use of the thermal cycle of the biochemical fluid sample, the isothermal temperature source with a large surface area was designed, fabricated and its thermal characterization was experimentally evaluated. The comprehensive overview of the technology trend on the temperature control devices was detailed. The large surface area isothermal temperature source was realized by using the vapor chamber heat spreader. The cost-effectiveness and simple manufacturing process were achieved by using the metal-etched wick structure. The temperature distribution was quantitatively investigated by using IR temperature imaging system at equivalent temperatures to the PCR thermal cycle. The standard deviation was measured to be within 0.7$^{\circ}C$ for each temperature cycle. This concludes that the presented isothermal temperature source enables no temperature gradient inside bio-sample fluid. Furthermore it can be applied to the cooling of the electronic devices due to its slimness and low thermal spreading resistance.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.12
• /
• pp.1031-1037
• /
• 2015

Laser assisted machining (LAM) is an effective method with which to effectively process difficult-to-cut materials. Simple machining processes, such as turning and linear tool paths, have been studied by many researchers. But, there are few research efforts on LAM workpieces using threedimensional shapes because of difficulties controlling the laser heat on workpieces with inclined angles or curved surfaces. Two methods for machining three-dimensional workpieces are proposed in this paper. The first is that the heat source shape and laser focal length are maintained using an index table. Second, a rotary type laser module is controlled using an algorithm to move the laser heat source in all directions. This algorithm was developed to control the rotary type laser module and the machine tool simultaneously. These methods are verified by a CATIA simulation.

• Journal of the Korean Solar Energy Society
• /
• v.25 no.4
• /
• pp.37-44
• /
• 2005

An experimental study was conducted to analyze performance of a heating system with variation of control logic of the system. The system uses a solar as heat source and composed with heat pump that uses R-22 as working fluid. The difference between the developed system and the commercially available heating system is working fluid. The solar assisted heating system which was widely distributed in the market uses water as a working fluid. It could be freezing in case of the temperature drops down under freezing point. The anti-freezing fluids such as methyl-alcohol or ethylene-glycol are mixed with the water to protect the freezing phenomena. However, the system developed in this study uses a refrigerant as a working fluid. It makes the system to run under zero degree temperature conditions. Another difference of the developed system compare with commercial available one is auxiliary heating method. The developed system has removed an auxiliary electric heater that has been used in conventional solar assisted heating system. Instead of the auxiliary electric heater, an air source heat exchanger which generally used as an evaporator of a heat pump was adapted as a backup heating device of the developed system. As results, an efficiency of the developed system is higher than a solar assisted heat pump with auxiliary electric heater. The merit of the developed system is on the performance increment when the system operates at a lower solar energy climate conditions. In case of the developed system operates at a normal condition, COP of the solar collector driven heat pump is higher than the air source heat exchanger driven heat pump's.

• Journal of Bio-Environment Control
• /
• v.21 no.4
• /
• pp.372-378
• /
• 2012

This study was carried out in order to determine the optimum length of a roll type PE pipe heat exchanger employed in the water-to-water heat pump system using the waste heat of the heated effluent flowed out from thermal power generation plants as a heat source. And the heat pump system of 30 RT for an experimental test was designed and manufactured. And also PE pipes were employed to recover the waste heat from the heated effluent. The inside diameter of PE pipe heat exchanger was 20 mm, the thickness was 2 mm and the diameter of a roll was 1,000 mm. And from the results of this study, we found that the optimum length of PE pipe heat exchanger was 75 m per the heat pump capacity of 1.0 RT (3.51 kW) and then the heating COP of heat pump system was 3.8.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.14 no.2
• /
• pp.108-117
• /
• 1985

In this study, a numerical analysis was performed for the natural convection heat transfer in a vertical channel which was consisted of two finite-thickness vertical walls with heat source. The ratio of the thermal conductivity of wall to air played an important role in the analysis. The case for which one side wall has protrusion resistances was also examined. The governing equations for the system was discretized by control volume formulation and solved by SIMPLE method. As the result of this study, it was found that the uniform heat flux boundary condition could be applied when the conductivity ratio was below approximately 50 and the uniform temperature boundary condition could be used when the conductivity rat io was over approximately 15,000. However, when the conductivity ratio was between 50 and 15,000, the thermal conductivity ratio value should be considered for the analysis. It was also found that the existence of protrusion resistance influenced the thermal field up to the distance of 3-4 times of the protrusion length.