• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.9-15
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• 2008

In this paper, we suggest PI control with a predictive controller to progress both energy saving and coefficient of performance(COP) in a variable speed refrigeration system. The capacity and superheat are controlled simultaneously and independently by an inverter and an electronic expansion valve respectively for saving energy and improving COP in the system. The refrigeration system has long dead time in superheat inherently. The dead time makes the system difficult to achieve the satisfactory quick control response, especially superheat control response. In order to solve this problem, we designed a predictive controller based on PI control to progress superheat control performance. The control performance was investigated through some experiments to verify the effectiveness of the predictive controller.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.925-931
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• 2000

Refrigerating ability of vapor compression refrigerator is decided by the harmonic work of it's components such as compressor, condenser, evaporator, expansion device, and so on. In this study, choosing refrigerant injectors as a new one of expansion device, temperature change of the cold room, ice freezing ability, and power consumption on flowrate of injector and refrigerant charging condition are evaluated experimentally. As the results of this study, it is verified that the spray injection type refrigeration system has some merits according to the flowrate and spray pattern of injector and charging quantum of refrigerant. And there are some design factors such as spray pattern and shape of spray chamber to utilize and fabricate this refrigerant injection type refrigerator.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.1-8
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• 2000

Spray as a liquid atomization technique has wide applications of combustion, painting, chemical, medical and agricultural purpose, and so on. Capillary tubes and expansion valves, as an expansion device of vapor compression type refrigerators, has been used from the early time. But there are some problems in practice, the former can't control refrigerant flowrate exactly and the later most of imported are expensive relatively and has some difficulties to install. Choosing an injector as a new concept of expansion device of refrigerator in this study to improve such troubles of the coming expansion device, the refrigerant spray behavior and refrigeration characteristics are evaluated experimentally. It is verified that the injector with a good function of refrigerant atomization plays a desirable role of refrigerant expansion in the actual refrigeration cycle.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.2
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• pp.25-32
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• 1994

The characteristics of the R-22 two-stage compression refrigeration systems were investigated. The apparatus consisted of 0.5HP and 1HP hermetic reciprocating compressors for the high and low stage sides respectively, a condenser, an evaporator, a heat exchanger, four expansion valves, and two intercoolers. The experiments covered a range of refrigerant flow rates from 24 to 84kg/h, and the inlet temperature of cooling water in the condenser and heat source water in the evaporator ranged from 20 to 30$^.\circ}C$The results Showed that the refrigerant flow rate had greater effect on the refrigerating capacities, the compression efficiency and the coefficient of performance of two-stage compression systems than the inlet temperature of heat source water. And all these values were decreased with increasing inlet temperatures of the cooling water. The pressure drops in the evaporator of two-stage compression systems were decreased in proportion to the increase in the inlet temperature of the heat source and cooling water, but it was increased by the refrigerant flow rate.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.44-52
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• 1996

Acoustical characteristics of internal pipe structures and a loudspeaker of the thermoacoustic refrigerator are analyzed by using the transfer matrix method. The resonator system is dismantled into verious basic acoustic elements, and then linearized transfer matrices are serially combined with the dynamical system of linearized loudspeaker model, that the total system of thermoacoustic refrigerator can be analyzed in terms of frequency characteristics and acoustic field shape. Additionally, by using equations for energy flow through the capillary stack, the temperature distribution over the stack is numerically estimated. After expressing the acoustic work flow, thermoacoustic flow, and energy loss per unit length in a single capillary duct by using the transverse functional variations, overall energy flow rate and energy balance are obtained for the whole capillary stack. The final expression for energy flow through the stack is numerically evaluated by varying physical parameters obtained from the sound field analysis. After confirming good agreements between predicted and experimental results for the interior sound field of a refrigerator model, the thermoacoustic characteristics of Hofler's apparatus is analyzed by the proposed method and it is observed that the results agree well with Hofler's experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.683-694
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• 1998

The application of hydrocarbon refrigerants in a hermetic reciprocating compressor for refrigerator is investigated. The selected refrigerants are isobutane(R600a), propane(R290), R12, binary mixture of R600a/R290, and OS-21CII. Both theoretical and experimental investigations have been performed for the selected refrigerants. The test results of hydrocarbon refrigerants have been compared to the traditional refrigerant(R12). The results show that hydrocarbon refrigerants(HC-Blend, OS-21C II) are very good alternatives in the refrigeration system for R12.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.647-650
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• 2002

A thermoacoustic refrigerator, using a resonant standing acoustic wave, has been built. It employs a loudspeaker to sustain a standing wave in a resonance tube. The stack of plates is 0.075mm-thick plastic sheet(Mylar), spirally wound to make a 40mm-diameter assembly 80mm long. and two heat exchanger are installed. The refrigerant is Helium gas. The description of thermoacoustic refrigerator are presented. The directly measured performance of the resonator. Tc/Th ( temperature ratio ) and $COP/COP_{c}$, (normalized by carnot's COP ) are plotted versus the thermal load Q applied to the cold end, for various speaker power.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.5
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• pp.269-276
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• 2015

Single-effect $CH_3OH-LiI-ZnBr_2$ and $C_2H_5OH-LiI$ absorption heat pumps are simulated to evaluate feasibility as heating device. These systems are predicted to give higher heating COPs in wide operating ranges compared to conventional systems. Among the two systems, the $C_2H_5OH-LiI$ system is found to be more advantageous for operating in extremely cold weather due to the large solubility of Lil in $C_2H_5OH$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.2
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• pp.130-139
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• 1994

A cycle analysis was performed for 2-stage expansion Claude refrigerators by a numerical method. The refrigerators are under recent development such that the reciprocating expanders of Collins cycle are replaced by new turboexpanders. A computer simulation program was written to predict the coefficient of performance of the refrigerators for several input parameters. It was found out that there exist unique optimum values for the ratio of expanded mass through the turboexpanders to the total mass and for the intermediate pressure of the 2-stage expansion. The maximum coefficient of performance was about $5{\times}10^{-4}$ at the optimal operation.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.115-119
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• 2008

지구 자원고갈과 환경오염으로 인한 에너지 절약에 대한 관심은 최근 국제유가 상승에 의해서 국가의 사활을 건 정책으로 반영되고 있다. 하루 중 부하변동이 심하지 않으면서 각실 제어가 필요하지 않은 조건을 갖춘 공간에는 지역난방공사로부터 온수를 공급받아 건물을 냉방하는 방식이 일반적으로 보급되어 있다. 최근 에너지의 유효이용 측면에서 온수 온도차를 늘려 냉방 에너지 보급용량의 확대 및 설비비용을 절감하려는 움직임이 진행되고 있다. 에너지 절약 측면에서 접근하여 볼 때 효율을 상승시키는 방법과 이용열원의 극대화가 동시에 검토되어야 하며 각각의 장점이 있는 현장에 맞추어 다양한 방식이 적용되어야 할 것이다.