• 설비공학논문집
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• 제17권3호
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• pp.201-208
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• 2005

This study presents the experimental study on improvement of frost/defrost performance in an heat pump system with newly developed fin and multiple compressors. As multiple compressors system, the variable and single speed compressor combinations has been introduced and compared with single speed 1-compressor system in a view point of improvement of frost/defrost performance. Also, newly developed corrugate shaped fin has been compared with conventional louver shaped fin. The frost/defrost performance is defined and some parameters are compared to discuss the effect of each combination. From this experimental study, it is known that if the variable and single speed compressor combination system equipped with corrugate shaped fin, the system performance has greatly improved not only for heating capacity, but also for frost performance.

• 설비공학논문집
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• 제23권12호
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• pp.782-790
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• 2011

Typical temperature control methods of a cooler for machine tools are hot-gas bypass and compressor variable speed control. The hot-gas bypass system has been widely used to control the cooler temperature in many general industrial fields. On the contrary, the compressor variable speed control is focused on special fields such as aerospace and high precision machine tools which need high precision control. The variable speed control system usually has two control variables such as target temperature and superheat. In other words, the variable speed control system is basically multi-input multi-output(MIMO) system. In spite of MIMO system, the proportional integral derivative(PID) feedback control methodology that based on single-input single-output (SISO) system is generally used for designing the variable speed control system. Therefore, it is inevitable to describe transfer functions for dynamic behaviors of every controlled variables and decide the PID gains with tremendous iteration process. Moreover, the designed PID gains do not provide optimum system performances. To solve these problems, high performance controller design method based on a state space model is suggested in this paper. An optimum controller is designed to minimize both control errors and energy inputs. This method was more simple to describe dynamic behaviors and easier to design the cooler controller which is MIMO system.

• 설비공학논문집
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• 제15권1호
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• pp.25-31
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• 2003

This paper addresses an oil supply enhancement device to resolve a shortage of oil supply or no oil supply at all encountered at low speed operation for a variable speed reciprocating compressor used for household refrigerators. The oil supply enhancement device comprises a moving cylinder attached to the lower end of crankshaft and two of fluid diodes, each one at the inlet and outlet of the cylinder. Up-and-down movement of the cylinder against the lower end of the crankshaft together with the functioning of the two fluid diodes produces net oil flow from oil reservoir to inside the crankshaft. The experiment on the test bench has shown that enough oil supply into the oil feeding hole cu be made by using this device even at low speed range. Some analytical study has also been carried out to under-stand its oil supply mechanism.

• Journal of Advanced Marine Engineering and Technology
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• 제34권2호
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• pp.282-288
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• 2010

본 연구는 전자팽창밸브의 개도변화에 따른 가변속 수냉각기의 용량제어 특성에 관한 논문이다. 인버터에 의한 가변속 압축기를 사용한 냉각기를 최적으로 제어하기 위한 선행 연구이며 압축기 회전수별로 제어대상인 전자팽창밸브를 조절하여 증발기 출구의 과열도를 일정한 값으로 제어함으로써 최적의 냉각능력을 얻을 수 있는 과열도 값을 찾는 것을 목표로 하였다. 본 실험의 결과 압축기 회전속도가 일정할 때 팽창 밸브의 개도변화에 따라서 냉각능력이 최대가 되는 지점의 개도량을 실험을 통해서 파악할 수 있었다.

• 설비공학논문집
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• 제13권8호
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• pp.746-756
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• 2001

An experimental study was conducted to investigated the effect of refrigerant flow control on the performance of a variable-speed heat pump operating in both cooling and heating mode. For this purpose, cooling and heating capacity, EER and refrigerant mass flow rate corresponding to an electronic valve as well as a capillary tube were measured as functions of compressor speed, length of capillary tube (or valve opening of the electronic valve), refrigerant charge, and outdoor temperature. From the comparison of experimental results, it was found that the performance variation due to the electronic valve opening became significant as the operating conditions(outdoor temperature and compressor speed) deviated from the standard condition at which heating capacity and EER were rated for the indicated capillary tube.

• 설비공학논문집
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• 제13권8호
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• pp.780-786
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• 2001

For the compressor speed control of a multi-type air conditioning system, a fuzzy control algorithm was developed. The sum of zone temperature errors and its derivative were used as input variables, and the compressor speed was selected as the output variable. To test the effectiveness of the control algorithm, one outdoor environmental chamber and four indoor environmental chambers were used. In the chambers the zone temperature step change test and the indoor unit change over test were performed. Test results showed that, for the control of compressor speed, the fuzzy control algorithm was more effective than the conventional proportional control algorithm for the energy conservation.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1123-1131
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• 2002

An experimental study on the performance and instability development characteristics of a centrifugal compressor equipped with a cambered variable diffuser has been performed with varying diffuser vane angles. The test was conducted at the design speed of 20,800 rpm and the 80% design speed of 16,640 rpm for 5 diffuser angles : 65$^{\circ}$, 70$^{\circ}$, 75$^{\circ}$, 77.5$^{\circ}$, 80$^{\circ}$ The steady performance test results showed that choking mass flow rate decreases and total pressure ratio increases with a narrowed surge margin as the diffuser vane angle increases. Unsteady pressures were measured using high-frequency pressure transducers at the inducer and the diffuser throat to investigate the instability phenomena such as rotating stall and surge inside the compressor. From the unsteady measurements, it is found that the transient process from rotating stall to surge was mainly affected by diffuser angles. The results of the present study can be applied to the instability control of the centrifugal compressors using a variable diffuser.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.474-479
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• 2005

For the safe operation of an air conditioner, the liquid car η 'over to compressors should be minimized and compressors should be operated in the specified region of suction and discharge pressures recommended by compressor manufactures. In this study, a capillary assisted tandem-type airconditioner was considered. A variable speed outdoor fan was used to control operating points of the system. Test results showed the possibilities to move system operating points to the safe region by controlling the speed of an outdoor fan.

• 한국정보통신학회논문지
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• 제6권6호
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• pp.879-884
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• 2002

산업 현장에서 필수적인 설비인 공기 압축기는 스크루, 왕복동 및 터보 압축기가 사용되고 있다. 근래에 터보 압축기가 넓이 사용되고 있는데, 터보 압축기는 구조적으로 임펠러를 고속회전 시켜야한다. 범용전동기에 높은 기어비를 가진 기어박스를 이용하여 구현하였는데, 이는 관성 모멘트, 마찰손 및 압축기의 크기를 증가시켰다. 최근에 터보 압축기의 연구는 초고속 동기전동기를 장착하여 기어박스를 제거하여 크기와 마찰손을 최소화하는 방향으로 진행되고 있다. 본 연구에서는 150마력 70,000rpm 직접 구동방식의 터보 압축기를 개발하기 위하여 초고속 동기전동기 센서리스 벡터 구동시스템을 개발하였고, 이를 적용하여 직접 구동방식 터보 압축기를 개발하였다.

• 신재생에너지
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• 제7권4호
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• pp.30-36
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• 2011

The objective of this study is to investigate the effects of the refrigerant charge amount on the performance of a water-to-water ground source heat pump with a variation of compressor speed and the secondary fluid flow rate. The water-to-water ground source heat pump was tested by varying refrigerant charge amount from -40% to 20% of full charge. Compressor speed was changed from 30 Hz to 75 Hz and the secondary fluid flow rate was adjusted from 6 LPM to 14 LPM. For all test conditions, EWTs of an indoor heat exchanger and an outdoor heat exchanger were maintained at standard conditions of ISO 13256-2. The slope of the COP with the variation of charge amount is much steeper at undercharged conditions than that at overcharged conditions. For all compressor speed, the variation of the system performance according to charge amounts showed the similar trends. However, the optimum charge amount of the system increased a little with an increment of compressor speed. When the secondary fluid flow rate decreased, the system was optimized at higher refrigerant charge amount conditions.