• Journal of Korean Society of Water and Wastewater
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• v.13 no.1
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• pp.95-112
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• 1999

In this research, it is proposed that optimization method is introduced and applied to the design of pipeline system in multi-regional water supply project, which has been constructed to settle the regional unbalance problems of available water resources. For the purpose, interface programs are developed to integrate linear programming model and KYPIPE model which is used for optimization and hydraulic analysis, respectively. The developed program is applied to the pipeline system design of multi-regional water supply project. The optimal diameters from the application of linear programming technique are compared with those from conventional method that is time-consuming and tedious trail and error process. Since the conventional design largely depends upon the experience of designers and the results of general hydraulic analysis, it can not be reasonable and consistent. The application of linear programming technique can make it possible to design pipeline system optimally by using same design factors of general hydraulic models. The model can select commercial discrete pipe diameter as optimal size by using pipe length as decision variables. The developed model is applied to Pohang multi-regional water supply system design with two different objective functions, which are initial construction cost and annual cost including electric cost. As results, it is calculated that the initial construction cost of 1,449,740 thousand won is saved and annual cost of 128,951 thousand won is saved for a year within study year. Also, the optimal site of pump station is selected on 5th pipe, which is located between the diverging junction to Kangdong(2) province and the diverging junction to Cheonbuk province. It is explained that pump cost is less than pipe cost in this application case study due to little pump station scale. In the case of water supply with large pump capacity, it is reasonal that the increase of pipe size is more efficient instead the increase of pump station capacity to save annual cost.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.168-176
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• 1998

A simulation study was conducted to use city-water which is thermally regulated by unused energy as a heat source for urban dwellings. This study utilized multiple heat pump system using the city-water as a heat source and suggested a method of reducing the heat load of hot water supply. The simulation was done to calculate the energy savings at a dwelling for a year. The relation between the controlled temperature of city-water. and electric energy in all seasons was also investigated. Furthermore, it has been found that the controlled water system can lead to considerable energy savings and decrease environmental load such as sensible waste heat which otherwise would form heat islands.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.41-46
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• 2011

In the present work, a new freeze protection method has been proposed for a natural circulation system of solar water heater. Though electrothermal wire is popularly used for the purpose, there are freezing troubles by wire cut-off and excessive electric power consumption. In the experimental device, hot water in a storage tank was circulated by a small pump and used to heat the outdoor pipes if the cold water pipe surface temperature falls lower than a set point. As a result, It was observed that there was no hot water waste while the solar water heating system operated without freeze and burst.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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• pp.50-59
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• 1992

A critical speed analysis of a pump shaft has been investigated. Among various methods in the shaft critical speed calculation, a transfer matrix method has been examined in this research. After a brief review on the transfer matrix method, a modeling procedure for a continuous structure has been discussed. Then, a critical speed of a multistage pump shaft has been estimated up to several low modes. Throughout an analysis, parametric effects on the bearing stiffness, a degree of the modeling order, and attachmant of the impeller have been investigated. As an application example, a critical speed analysis of a verical pump which has been implemented in domestic electric power plants for cooling water circulation has been conducted in order to provide a safe operation as far as a pump vibration is concerned.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.37-39
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• 1999

In this paper, the magnetic fluid linear pump is designed. Inside the small tube, magnetic fluid is shielded with thin rubber protector. The magnetic fluid activated by traveling pulses of magnetic field drags the water inside the pump. The iterative algorithm for the shape of magnetic fluid is presented by using nonlinear finite element method and Navier-Stokes equations. The computed curvature of fluid under the magnetic field and the gravitational force is agreed well with photograph image. The dimension and electric configurations of the magnetic linear pump are optimized and the results are compared with measurements.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.880-885
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• 2009

The ships have a lot of electric machinery needed to supply electricity from the moment of launching coming out of dry dock to docking at jetty. Thus, the ships always have to use alternator and electric machinery that has low efficiency under the low load. Many government service ships like the MMU training ship have been spending lots of time at jetty rather than sailing at sea. These ships are operated under the condition of low load due to the operation of basic machinery at jetty and electric machineries are driven with the status of low efficiency. This paper would suggest the energy saving method for these ships. The investigation describes that shore connection is a great asset to these ships and that the flow rate control by adjusting revolution with the adoption of inverter is better than flow rate control by using throttle valve to save energy. The result is based on the investigation of cooling pump at MMU training ship.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.4
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• pp.27-32
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• 2016

It is estimated that only heating and cooling take about one third of the total energy consumption worldwide. However, the conventional heating and cooling systems have low efficiencies. Also, boilers and electric heaters that are mostly used to generate both domestic and industrial hot water are inefficient and high energy consumers. For this reason, cascade heat pumps which are known to be very energy efficient and have less environmental impact are being promoted to replace conventional heating, cooling and hot water systems. In this study, a newly designed cascade heat pump by two-stage water heating method has been experimentally investigated. By adopting the auxiliary heat exchanger, the performance of the system was increased. The performance enhancement rate of the system could be maximized by adjusting the low stage compressor speed rather than the high stage compressor speed. The performance of the system with the auxiliary heat exchanger was enhanced by 16.5%.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.18-22
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• 2006

Hydrodynamic performance test was conducted for a fuel pump of a liquid rocket engine turbopump. The pump driven by an electric motor was tested using water. It is experimentally shown that the inducer had very small effect on the pump's head and efficiency but great effect on the pump's cavitation performance. Additionally, inducer test was carried out to investigate the effect of the inducer on the pump in detail, and it was found that the pump reached a critical cavitation number when the inducer head dropped by 55%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.495-501
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• 2013

In the present study, a BLDC motor for a pump in which a neodymium PM is replaced with a Ferrite PM has been developed in preparation for the cost increase and to ensure the stability of the resource supply. One of the currently used motors for pumps is a BLDC motor having an interior PM wherein a rare-earth PM is adopted. However, a BLDC motor for a pump is designed to have large airgap because of the use of a waterproof insulator according to its structural characteristics, and therefore, a SPM structure is suitable. Hence, an SPM BLDC motor in which a Ferrite PM is used is designed. Nevertheless, the use of Ferrite instead of rare-earth materials causes a deterioration in the performance of the electric motor, such as a decrease in the BEMF and the maximum power of the motor and the irreversible demagnetization of the PM. In order to mitigate such disadvantages, an optimized design of the BLDC motor is developed by changing each design parameter and by improving the electromagnetism structure.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.89-95
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• 2015

Performance test was conducted for an oxidizer pump and a fuel pump for a 7 ton class rocket engine, by using water. The pumps were driven by an electric motor. The hydrodynamic performance and the suction performance were measured at flow ratio of the design and off-design conditions. Head-flow curve, efficiency-flow curve, and head-cavitation number curve were obtained. It is confirmed that the pumps can satisfy the design requirements of hydrodynamic performance in terms of the head and the efficiency. The pumps also satisfied the design requirements of suction performance.