• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.513-519
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• 2011

The object of this study is to investigate the performance characteristics of refrigerators using a single-circuit multi cycle and a bypass two-circuit multi cycle. Each refrigeration cycle was tested by varying secondary fluid mass flow rate and temperature. Based on the experimental data, the optimum refrigerant charge was 48 g and the COP at the optimum secondary fluid mass flow rate was 1.53 for the single-circuit multi cycle. For freezer(F)-only mode, both the single-circuit multi cycle and the bypass two-circuit multi cycle were operated at overcharge conditions, resulting in an increase of the secondary fluid mass flow rate. The maximum COPs of the single-circuit multi cycle and the bypass two-circuit multi cycle were 1.22 and 1.35, respectively. The COP increased by 10.7% with the application of the bypass two-circuit multi cycle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.3
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• pp.210-215
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• 2002

In this study, the computer program called Multi_Cycle, which simulates the steady-state performance (coefficient of performance, capacity, power consumption and etc.) of multi- airconditioning systems using R410A, was developed. In order to validate the simulation program, a series of case studies were carried out. The Multi_Cycle consists of several subroutines for simulating indoor units. outdoor unit, compressor, and expansion devices. and for estimating the thermodynamic and transport properties of the refrigerants and moist air. It would appear to be advantageous to use the Multi_Cycle for a performance analysis when considering various kinds of refrigerants and the complex operating conditions of each unit making up the multi-airconditioner cycle. Moreover, the Multi_Cycle would seem to be useful tool in optimizing a multi-airconditioning system and establishing economical and efficient operating conditions in the multi-airconditioner cycle. In the present study, the Multi_Cycle was programmed with Digital Visual Fortran for the main simulation code and Visual Basic for- the graphic user interface.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.11-17
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• 2016

In this study, the simulation for performance comparison between basic single stage organic rankine cycle, multi stage reheater cycle and multi stage reheater & recuperator cycle was carried out. The multi stage reheater cycle and multi stage reheater & recuperator cycle was designed to improve the efficiency for organic rankine cycle using heat source from industrial waste heat and heat sink from deep ocean water. R245fa was selected as a refrigerant for the cycle and system efficiencies were simulated by the variation of the heat sink temperature and the cycle classification. Performance characteristics were simulated by using the Aspen HYSYS. It was confirmed that the system efficiency was decreased by the increase of heat sink temperature. These results can be considered to be applied as geo-ocean thermal energy conversion in where plenty of geothermal or ocean thermal resource exist.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.3
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• pp.129-138
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• 2014

This paper is to analyze the cycle time of the vendor in a single-vendor multi-buyers supply chain. The vendor is the manufacturer and the buyers are the retailers. The cycle time of the vendor is the elapse time from the beginning time of the production to the beginning time of the next production. The cycle time of the vendor that minimizes the total cost in a supply chain is analyzed. The cost factors are the production setup cost and the inventory holding cost of the vendor, the ordering cost and the inventory holding cost of the retailers. The cycle times of the vendor obtained with the costs of the vendor is compared with those obtained with the costs of the vendor and the retailers. Various numerical examples are tested if the cycle times of the vendor for both methods are the same.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.116-121
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• 2014

In order to study the improvement of the multi stage regeneration cycles, muti-stage processes were applied to the cycles, respectively or together. The kinds of the cycles are multi stage reheater cycle (MS) and multi stage reheater regeneration cycle (MSR). Working fluid used was R134a and R245fa. Temperature of the heat source was $65^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$, and temperature of the heat sink was $5^{\circ}C$. Optimization simulation was conducted for improving the gross power and efficiency with multi stage reheater regeneration cycle for ocean thermal energy conversion(OTEC) with changing of a heat source, kind of the working fluid, and type of the cycle. Performance analysis of the various components was simulated by using the Aspen HYSYS for analysis of the thermodynamic cycle. R245fa shows better performance than R134a. This paper showed the most suitable working fluid with changing of a heat source and the kinds of working cycle. Compared to each other, MS showed better performance at gross power and MSR showed higher cycle efficiency.

• Advances in materials Research
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• v.7 no.3
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• pp.195-201
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• 2018

High Strength low alloy steels containing various levels of C, Nb and Mn were used and for each of which, a simulated double thermal cycle was applied with the same first peak temperature and different second peak temperatures to produce HAZ microstructure corresponding to multi-pass weld. Effect of double cycle second temperature on the microstructure was observed and compared with single cycle results obtained from previous works, it was found that the percentage of martensite austenite constituent (MA) increases by Nb addition for all steels with the same Mn content and the increase in Mn content at the same Nb content shows an increase in MA area fraction as well. MA area fraction obtained for the double cycle is larger than that obtained for the single cycle for all steels used which imply that MA will have great role in the brittle fracture initiation for double cycle and the inter-pass temperature should be controlled for medium and high-carbon Mn steel to avoid large area fraction of MA. The beneficial effects of Niobium obtained in single pass weld were not observed for the double cycle or multi pass welds.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.59-67
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• 2023

This paper explores the variation of DC-Link current ripple analysis in terms of duty cycle and phase angle of Multi-phase/Multi-stage boost converter. A 2-Stage/1-Stage boost converter DC-Link current is used to determine the difference between the 1st stage diode current and the 2nd stage inductor current. Each stage boost converter diode and inductor current is subordinate to the phase angle and duty cycle. The magnitude of the ripple current is variable according to phase angle and duty cycle. The analysis results are verified by variation of DC-Link current ripple using a 1kW typical 2-stage/1-stage boost converter.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.459-464
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• 2009

This study has been conducted on how to determine the multi-evaporator vapor compression cycle system is charged correctly by using sensor readings which are used to control system. In this paper, the characteristics of the multi-evaporator were presented and sensor values were classified using fuzzy clustering. finally classification logic and it's performance were discussed by applying commercial VRF system.

• Journal of Korean Society for Quality Management
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• v.41 no.3
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• pp.413-421
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• 2013

Purpose: System availability and life cycle cost are often used to evaluate the system performance and is influenced by the operation and maintenance characteristic. In this paper, we propose the method to improve life cycle cost and satisfy the target availability through redundancy allocation. Methods: We consider the redundancy is available at all items in multi level system. Thus, we assume that sub-assembly, module, components can be duplicated. Simulation and genetic algorithm are employed to optimize redundancy allocation. Results: Target availability is higher, the life cycle cost is increased. In addition, the items for redundancy are selected at higher level in multi level system if target availability is higher. Conclusion: We could know that target availability affects the duplication number of items and the selection of redundancy items. For further study, we will consider new optimization algorithms to compare with the proposed GA algorithm and improve optimization performance.

• KSBB Journal
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• v.18 no.2
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• pp.122-126
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• 2003

Multi-cycle chromatographic separation of Iysozyme from egg white was investigated. Multi-cycle chromatography was performed by repeated cycling(one cycle: resin equilibration, sample loading, washing, elution). Two types of cation exchange resins, Cellufine CM C-200 and Bio-rex 70, were used to determine the optimum condition for the separation of Iysozyme by multi-cycle chromatography. The resin was equilibrated in 20 mM Na-phosphate buffer(pH 7.0). Chromatograms of UV absorbance levels of every cycle were compared to confirm the eluting ability of Iysozyme in the two types of gel. Collected samples from eluting regions in every cycle were assayed by 15% SDS-PAGE.