• Journal of Advanced Marine Engineering and Technology
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• v.38 no.1
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• pp.8-14
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• 2014

This research designed Waste Heat Recovery System(WHRS) generation system of 250kW whose working fluid is R-245fa and studied on cycle characteristics by superheater organization. It simulated two conditions; series connection and parallel connection between superheater and evaporator. In simulation of series connection of superheater and evaporator, output of 4.7% could be improved because of the increase of enthalpy by overheating of working fluid. When setting 250kW for target output, cycle flux could be reduced by 4.1%. When setting 250kW as a target output of cycle In parallel connection simulation of superheater and evaporator, cycle flux was reduced as flux of heat source fluid for superheater was increased. So, the maximum 7.9% of working fluid pump's electric power was reduced and there was no big change in cycle efficiency and net efficiency by flux ratio.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.53-58
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• 2015

Systemic heating and cooling air conditioning systems are popular in various industrial fields and even home. Recently, the rate of supply of this kind of multi-heat pump has been increased under ESCO financing supporting system. Generally the heat pumping system has a structural simplicity and easy installation benefits. and has good running efficiency under normal designed condition. But under extreme climate condition (over $+30^{\circ}C$, under $-10^{\circ}C$), this system exposes abnormal power consumption. It causes high progressive electric power rates and resultant peak power capacity of power plant. In this paper, a novel system concept of buffering refrigerant accumulator and constant pressure control system to relieve peak power load is proposed and this system's utility is verified with an prototype experimental system.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.107-121
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• 2020

The performance analysis of the small satellites launch vehicle using the electric pump cycle as the upper stage engines was performed. The first stage is the launch vehicle that uses the test launch vehicle of the Korea Space Launch Vehicle II and the second stage employs elecpump cycle engine that uses liquid methane and kerosene (RP-1) as fuel. A model for the mass estimation was presented and the analysis was conducted for the range of thrust of 20 to 40 kN and combustion pressure of 3 to 6 MPa with a nozzle expansion ratio of 60 to 100. The mixture ratio with the maximum velocity increment was calculated and the performance of the LEO and SSO payload were calculated from the stage mass estimation. In both the cases, liquid methane, and RP-1 showed maximum payload for 20 kN thrust, 3 MPa combustion pressure, and the nozzle expansion ratio of 100, with a mixture ratio of 3.49 for liquid methane and 2.75 for RP-1. In addition, the ditching points of the first stage and the fairing in the LEO mission were analyzed using ASTOS.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.3
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• pp.12-18
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• 2012

The purpose of this study is to make an economic analysis(Life cycle cost) of selecting optimal air conditioning system for a research building which is 8 stories with a total floor area of $32,010m^2$. Energy consumptions of three proposed air-conditioning systems(Alt-1,2,3) that reflect the government green-growth policy are calculated and compared. The results show that life cycle cost of Alt-3(Ventilation DX AHU+EHP) is less than Alt-1(EHP+ventilation DX AHU) by 5.1%, and Alt-2(Absorption chiller/heater+EHP) by 34.3%. Annual energy consumption of Alt-3 is less than Alt-1 by 9.9%, and Alt-2 by 37.4%. Annual $CO_2$ emission of Alt-3 is less than Alt-1 by 9.9%, and Alt-2 by 0.2%.

• Solar Energy
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• v.18 no.4
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• pp.23-32
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• 1998

Fuel cells supply electric power and heat at work, and their exhaust gas is comparatively clear. So they are in the limelight as one of the co-generation systems which behave friendly with the environment. Fuel cells discharge both steam and hot water. Accordingly, if we combine absorption heat pump driven by waste heat with fuel cells, we can construct an advanced energy conserving system. The purpose of this study is the objective for evaluating the possibilities of effectively utilizing waste heat of fuel cells as a heat source for the single and double effect absorption systems. Simulation studies on single and double effect absorption have been performed for water/lithium-bromide pair. The effectiveness of introducing a waste heat source of fuel cells is demonstrated. The result of this study showed that total efficiency was about 85% at rated operation and about 75% at 75% load operation. Absorption cycle moved to more strong concentration when fuel cell operated at 75% load.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.437-444
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• 2008

Many other countries have investigated the new backwash water treatment process to save the existing water resource. There are various methods for reusing backwash water, but the membrane system has received the most interest for its efficiency. The objective of this study was to certify the application of membrane filtration system for the backwash water treatment. The experiment equipment was composed of Lab scale tubular membrane filtration system. Generally, cross-flow operation mode is used in the tubular membrane system but cross-flow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, dead-end operation mode was used in this experiment. Filtration and bleed operation cycle was used in this membrane system. Backwash water was concentrated during the filtration process and when backwash water reached our target suspended solid concentration, it was discharged from this system. For efficient operation of filtration and bleed, mathematical matrix was drawn up and with this matrix we could simulate various sets of filtration and bleed time.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.91-102
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• 2020

Recently, a new space era has evolved in which commercial companies' led space development has begun. In this era, commercial companies actively participate in space development as the size of the small satellite market and small launch vehicle market is expanding. Through space development, developed countries are making efforts to reduce development, production, and operation costs to secure the competitiveness of small launch vehicles. In this study, the development trend of small launch vehicles and required technologies for space development were analyzed and summarized. Thus, research and development is urgently needed so that spin-on technologies, such as electric pumps and additive manufacturing, can be utilized for space development.

• Tribology and Lubricants
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• v.33 no.1
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• pp.23-30
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• 2017

The electric controlled marine diesel engine has fuel pump generating the high pressurized fuel for fuel injection to combustion chamber via a common rail. Fuel pump consists of a cam-roller system. Journal bearing installed between a roller and a cam-roller pin is subjected to fluctuating heavy and instant loads by cam lift. First, Kinematic analysis is carried out to predict bearing loads during one cycle acting on the journal bearing. Second, flexible multi-body dynamic analysis and transient elasto-hydrodynamic(EHD) lubrication analysis for journal bearing considering elastic deformation of cam-roller pin, roller and bearing are conducted using AVL EXCITE/PU software to predict lubrication performance. The clearance ratio and journal groove shape providing lubrication oil are important parameter in bearing design having good performance and can be changed easier than other design parameters such as diameter, width, oil supply pressure and bearing material grade. Generally, journal bearing performance is represented by the minimum oil film thickness(MOFT) and peak oil film pressure(POFP). As well as the traditional design parameters(MOFT, POFP), in this study, temperature rise of lubrication oil is also evaluated through the side leakage flow of supplied oil. By the evaluating MOFT, POFP and temperature rise, the optimum bearing clearance ratio is decided.

• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.41-48
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• 2015

The performance characteristics of a scroll expander is the most important variable for the performance of organic Rankine cycle system. In this paper, the performance characteristics of a scroll expander was identified using 1kW class organic Rankine cycle system with various operating conditions. The ORC system is composed of an evaporator, a scroll expander, a condenser and a working fluid feed pump that uses R245fa as working fluid. The hot water temperature was controlled from $80^{\circ}C$ to $115^{\circ}C$ by the 50kW-class electric water-heater. The maximum isentropic efficiency of the scroll expander was measured about 77%, and the shaft power was measured from 0.5 kW to 1.8 kW according to heat source temperatures.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.143-154
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• 2020

The mathematical modeling applying experimental coefficients to a conventional model was validated through the hydraulic test for the components and the full system of a small-sized liquid rocket engine's propellant supply system. According to the simulations, pressures difference for the fluid resistance components and the pump were mainly predicted. In order to improve the modeling accuracy, the loss coefficients obtained by the empirical method were applied to the modeling. Based on the governing equation of the flow or the well known empirical equation, the method of deriving the empirical coefficients was summarized and the coefficients were presented for the commercial products used in this study. The prediction results by modeling were in good agreement with the experimental data. Through the comparison with the experimental data, the factors affecting the accuracy of the simulation were analyzed and improving methods of the accuracy was proposed.