• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.10-20
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• 2004

Experiments have been conducted in order to make comparisons of characteristics of a R410a cycle with a R22 cycle in terms of cooling capacity and coefficient of performance (COP). The parameters examined in the present work include air flow rate, indoor and outdoor air temperatures, and indoor relative humidity. These two refrigeration cycles constructed for this study share all components except compressor, accumulator, oil separator, and piping. The measurements were made using a psychrometric calorimeter. The experimental results show that the R410A cycle has several advantages for indoor units while the R22 cycle yields better performance for outdoor units.

• 한국가스학회:학술대회논문집
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• 1998.09a
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• pp.255-260
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• 1998

This study describes the results of Coefficient Of Performance(COP) analysis by cycle simulation for two types of absorption-compression hybride cycle using the water/Lithium Bromide solution pair, These types are basic hybride systems introducing a mechanical compression process into the refrigerant vapor phase of the single effect absorption cycle. In absorption-compression hybrid cycles, coefficient of performance is improved compared with absorption cycle. Hybride cycle Type ll is considered as a key technology to support energy utilization system, given its capability of utilizing waste heat to drive system with a high level of efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.76-85
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• 2000

Stirling cycle was actualized as so called ‘hot air engine’. It has been focused again lately as one of measures for exhaust gas emission problem, but as small power engine because of its method of heat addition. Recently marine power plants commenced to meet a stringent environmental restrictions by international convention, Marpol so that diesel engines as main and auxiliarly power plants are urged to be reformed to reduce NOx emission. Author devised a compression ignition engine as a large marine power plants combined with turbo charger based on stirling cycle, and analyzed the performance by means of basic thermodynamic calculation. Analyzed in this paper, were theoretical efficiency, mean effective pressure, required equivalence ratio, gas turbine power ratio, maximum pressure, states of turbo-charger inlet gas and exhaust gas, manifesting that the engine could be proposed as one of the future power plants of marine use.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.923-929
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• 2001

The objectives of this paper are to develop an advanced GAX cycle named HGAX (Hybrid Generator Absorber heat eXchange) cycle, and to study the effect of key pa-rameters on the cycle performance and the evaporating temperature. Two different HGAX cycles are developed-Type A (Performance improvement) and Type B (Low temperature applications). A compressor is placed between the evaporator and the absorber, and the evaporator pressure and the absorber pressure are controlled according to its application purpose. It was found that the COP could be improved by 24% compared with the conventional GAX cycle and the evaporating temperature as low as -8$0^{\circ}C$ could be obtained from the HGAX cycle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.166-176
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• 2003

Experiments have been conducted in order to make comparisons of a alternative refrigerant (R-410A) cycle characteristic with an existing refrigerant (R-22) cycle characteristic in terms of cooling capacity and coefficient of performance (COP). The parameters examined in the present work include air flow rate, indoor/outdoor air temperatures, and indoor relative humidity. These two refrigeration cycles share all components except compressor, accumulator, oil separator, and piping connecting them. The measurements were made using an air-enthalpy calorimeter. The experimental results show that the R-410A cycle has many advantages over indoor conditions while the R-22 cycle has better performance over outdoor conditions.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.155-163
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• 2019

Mixture electrodes of a graphite having a good cycle performance and a silicon monoxide (SiO) having a high capacity are fabricated and their cycle performances are evaluated as negative electrodes for lithium-ion batteries. The electrode prepared by mixing the natural graphite and carbon-coated SiO in a mass ratio of 9:1 shows a reversible capacity of $480mAh\;g^{-1}$, 33% higher than that of graphite. However, the capacity deteriorates continuously upon cycling due to the volume change of silicon monoxide. In this study, the factors that can improve the cycle performance have been discussed through the change in the configurations of the electrode and the electrolyte. The electrode using the carboxymethyl cellulose (CMC) binder shows the best cycle performance compared to the conventional binders. The electrode sing the CMC and styrene-butadiene rubber (SBR) binder not only has almost the similar cycle characteristics with the electrode using the CMC binder but also has the better rate capability. When the fluoroethylene carbonate (FEC) is used as an electrolyte additive, the cycle life is improved. However, the electrolyte with 5 wt% of FEC is appropriate because the rate capability decreases when the content of FEC is increased to 10 wt%. In addition, when the mass loading of the electrode is lowered, the cycle performance is greatly improved. Also, enhanced cycle performance is achieved using the roughened Cu current collector polished by abrasive paper.

• 연구논문집
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• s.30
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• pp.5-13
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• 2000

The computation scheme of simulating gas turbine transient behavior was developed. The basic principles of this scheme and main input data required are described. Calculation results are presented in terms of whole operating regime of the cycle. The influence of main initial parameters such as starting engine power, moment of inertia of the rotor, fuel supplying schedule etc. on performance characteristics of has turbine during transient operation is studied In addition, bleeding air influence on transient behavior was also considered For validation of the developed code, comparison of present calculation with that of measurement data of the experimental data for the range of operating period studied.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.344-355
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• 2012

This study was conducted to analyze on the operational time and productivities of logging operations in whole-tree logging operation system by tower-yarder and swing-yarder, and in cut-to-length logging operation system by excavator with grapple in order to establish the efficient logging operation system and to spread logging operation technique. In the analysis of operational time, in case of whole-tree logging operation system, the felling time was 46.6 sec/cycle by chain saw, the yarding time was 480.6 sec/cycle by tower-yarder, the yarding time was 287.4 sec/cycle by swing-yarder and the bucking time was 155.14 sec/cycle by chain saw. In case of the cut-to-length logging operation system, the felling and bucking time was 225.65 sec/cycle by chain saw, the cut-to-length extraction time was 4,972 sec/cycle by excavator with grapple, the branches and leaves extraction time was 3,143 sec/cycle by excavator with grapple. The forwarding time was 4,688 sec/cycle by wheel type mini-forwarder, the forwarding time was 2,118 sec/cycle by excavator with grapple and small forwarding vehicle. In the analysis of operational productivities, in case of whole-tree logging operation system, the average felling performance was $57.89m^3/day$ by chain saw, the average yarding performance was $20.3m^3/day$ by tower-yarder, $31.55m^3/day$ by swing-yarder respectively, the average bucking performance was $20.3m^3/day$ by chain saw. In case of the cut-to-length logging operation system, the average felling and bucking performance was $11.96m^3/day$ by chain saw, the average cut-to-length extraction performance was $34.75m^3/day$ by excavator with grapple, the average branches and leaves extraction performance was $37.66m^3/day$ by excavator with grapple, the average length of operation road construction was 73.8 m/day by excavator with grapple. The average forwarding performance by wheel type mini-forwarder and the average forwarding performance by excavator with grapple and small forwarding vehicle was $15.73m^3/day$ and $65.03m^3/day$, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.446-453
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• 2000

The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consisted of the combination of oxygen, argon and recycled exhaust gas for obtaining underwater or underground power sources. this study has been carried out to analysis the performance of closed cycle system by means of investigation on the combustion characteristics of diesel engine MTU8V183TE52 operating in open, semi-closed, and closed cycle modes. The combustion in closed mode starts a little bit earlier than in open cycle mode. The oxygen concentration and fuel consumption at 240kW closed cycle running are 21∼24% by volume and 77∼79kg/h, respectively. The maximum cylinder pressure and ignition delay time are investigated 110bar and 8.9degree. Also, The combustion simulation program has been studied to predict whether or not combustion. The results from numerical prediction for the basic, cylinder averaged quantities such as the cylinder pressure and the heat release showed excellent with the experimental data.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.80-84
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• 2011

The cycle performance of closed ocean thermal energy conversion (OTEC) system with 50 kW gross power was evaluated to obtain the basic data for the optimal design of OTEC using waste heat such as solar power, discharged heat from condenser of power plant. The basic thermodynamic model for OTEC is Rankine cycle, and the surface seawater and deep seawater were used for the heat source of evaporator and condenser, respectively. The cycle performance such as efficiency, heat exchanger capacity, etc. was analyzed on the variation of temperature increase by waste heat. The cycle efficiency increased and necessary capacity of evaporator and condenser decreased under 50kW gross power with respect to the temperature increase of working fluid. Also, when the temperature increase is about $13.5^{\circ}C$, the heat which can be used is generated. By generator with 0.9 effectiveness under the simulated condition, the cycle efficiency was improved approximately 3.0% comparing with the basic cycle.