• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.402-407
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• 2008

This study is performed to investigate heat transfer characteristics for thermal performance of fin-and-tube sensible heat exchangers under the low air flowrate according to fin geometry combination and coolant flowrate control. Fins and tubes of samples were separated between front row and rear row. Experiment results are plotted heat transfer rate of each row, heat transfer coefficient and sensible heat ratio against water flowrate control of each row. It is observed that thermal performance can be enhanced by fin geometry combination and water flowrate control of each row under the low air flowrate.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권4호
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• pp.211-219
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• 2002

In this study, in-situ performance test of a wet surface finned-tube evaporator of an air source heat pump which has a rating capacity of 20 RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist. From the experimental data, air side heat and mass transfer coefficients were calculated by the well known heat and mass transfer analogy and tube-by-tube method. Since current procedure underpredicted the experimental sensible heat factor (SHF), a proper empirical parameter was introduced to predict the experimental data with satisfactory results. This study provides the method of evaluating the heat and mass transfer coefficients of a wet surface finned-tube evaporator of which in-situ performance test is necessary.

• 한국가금학회지
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• 제41권4호
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• pp.297-303
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• 2014

생애 초기 고온 적응은 이후 고온 스트레스를 받았을 때 닭이 고온 저항성을 획득하는데 도움을 주는 것으로 알려져 있다. 본 연구에서는 5일령의 고온 적응이 이후 고온 스트레스를 받은 육계의 생산성에 미치는 영향을 조사하였다. 초생추 아버에이커를 23시간 점등 1시간 소등의 조명 환경 조건을 가진 동일한 크기의 두 사육실에 수용한 후, 사료와 물을 자유로이 급여하였다. 5일령에 사전 고온 적응구는 24시간 동안 $37^{\circ}C$의 고온에 노출된 후 정상의 온도로 돌려졌고, 대조구에서는 정상적인 감온 일정에 따라 사육되었다. 21일령에 두 사육실의 육계는 각각 두 집단으로 나누어 총 4처리구(CON+CON: control+control; CON+HS: control+heat stress; HC+CON: heat conditioning+control; HC+HS: heat conditioning+heat stress)로 배치하였고, 이 상태에서 7일간의 환경 적응 기간을 가졌다. 28일령에 하나의 사육실에 있는 육계는 3일 동안 고온 스트레스($21^{\circ}C{\rightarrow}31^{\circ}C$)에 노출되었고, 대조구는 실온상태에서 사육되었다. 고온 스트레스 결과, 사료 섭취량 음수량 및 증체량이 유의적으로 감소한 반면(P<0.05), 직장온도와 폐사율은 증가하였다(P<0.05). 따라서 본 연구를 통해 사전 고온 적응의 효과성은 인정되지 않았으며, 이러한 결과는 사전 고온 적응의 효과는 종계의 나이나 계통의 차이에 따라 달리 나타날 수 있기 때문에 현장적용에 신중해야 할 것으로 사료된다.

• 한국기계가공학회지
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• 제9권6호
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• pp.59-65
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• 2010

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SCM415 steel. The control of heat-treatment deformation must need the progress of production parts for an industry machine. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for the part of the industry machine by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on the thermal deformation and fatigue strength are also investigated.

• 한국전자통신학회논문지
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• 제10권12호
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• pp.1395-1402
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• 2015

Electric heat tracing 시스템은 플랜트 내 각종 배관의 온도를 관리하는 시스템이다. 본 논문에서는 electric heat tracing 시스템을 통합적으로 감시하고 제어하기 위한 TESCON(: TEmperature Sensing and CONtrol) 시스템을 제안한다. TESCON 시스템에서 디바이스간의 정보 교환은 Zigbee 네트워크 기반의 무선 방식으로 이루어진다. TESCON 시스템의 성능 분석을 위해 컴퓨터 시뮬레이션을 수행하였다. 테스트베드를 통해서도 비슷한 결과를 얻음으로써 TESCON 시스템의 유효성을 입증하였다. 또한, 계층적 트리 토폴로지를 기반으로 하는 네트워크 분할, 채널 재사용, 프레임 집약 기법 등을 적용한 시스템 확장 방안도 제시하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.669-674
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• 2006

The optimal control of heat pump performance for heating mode operation was investigated. Fuzzy logic was applied to control the heating performance of heat pump system and superheat at compressor discharge was taken as a control variable. Regression model was adapted to determine the optimal points where COP is maximized. Optimization of fuzzy rule table was investigated to improve operation performance of heat pump system. Experiments were carried out using original fuzzy table and the modified fuzzy rule table for heating mode operation of heat pump system. The results show that control performance of heat pump system with the modified fuzzy rule table was better than that with the original rule table.

• 설비공학논문집
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• 제25권7호
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• pp.398-405
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• 2013

Small and medium-size buildings employ a multi-distributed individual air-conditioning system that utilizes package air conditioners instead of centralized cooling systems, which can allow easier building management and maintenance, along with a diversification of facility use. Inverter driven system heat pumps have been developed to achieve not only an easy distribution control, allowing free combination of indoor units with different models and different capacities, but also wide applications to intelligent air conditioning. However, the control algorithms of the system heat pump are limited in the open literature, due to complicated operating conditions. In this paper, an inverter-driven system heat pump having two indoor units with electronic expansion valves (EEV) was simulated in the cooling mode. An integral optimum regulating controller employing the state space control method was also simulated, and applied to the system-heat pump system, to obtain efficient control of the MIMO (multi input multi output) system. The simulation model for the controller yielded satisfactory prediction results. The new control model can be successfully utilized as a basic tool in controller design.

• 한국지열·수열에너지학회논문집
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• 제17권4호
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• pp.68-78
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• 2021

In order to solve the increasing deterioration of the energy shortage problem, ground-source heat pump (GSHP) systems have been widely installed. The control method is a significant component for maintaining the long-term performance and for reducing operation cost of GSHP systems. This paper presents the measurement and analysis results of the cooling performance of a GSHP system using capacity control with outdoor air temperature. For this, we installed monitoring equipments including sensors for measuring temperature, flow rate and power consumption, and then monitored operation parameters from July 9, 2021 to October 2, 2021. From measurement results, we analyze the effect of capacity control with outdoor air temperature on the cooling performance of the system. The average performace factor (PF) of the heat pump was 6.95, while the whole system was 5.54 over the measurement period. Because there was no performance data of the existing GSHP system, it was not possible to directly compare the existing control method and the outdoor air temperature method. However, it is expected that the performance of the entire system will be improved by adjusting the temperature of cold water produced by the heat pump, that is, the temperature of cold water on the load side according to the outside air temperature.

• 제어로봇시스템학회논문지
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• 제20권5호
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• pp.543-550
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• 2014

In many industrial processes and operations, such as power plants, petrochemical industries and ships, shell and tube heat exchangers are widely used and probably applicable for a wide range of operating temperatures. The main purpose of a heat exchanger is to transfer heat between two or more medium with temperature differences. Heat exchangers are highly nonlinear, time-varying and show time lag behavior during operation. The temperature control of such processes has been challenging for control engineers and a variety of forms of PID controllers have been proposed to guarantee better performance. In this paper, a scheme to control the outlet temperature of a shell and tube heat exchanger system that combines the PID controller with feedforward control and anti-windup techniques is presented. A genetic algorithm is used to tune the parameters of the PID controller with anti-windup and the feedforward controller by minimizing the IAE (Integral of Absolute Error). Simulation works are performed to study the performance of the proposed method when applied to the process.

• 열처리공학회지
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• 제13권5호
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• pp.330-336
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• 2000

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SM45C steel. The control of heat-treatment deformation must need the progress of production parts for a landing gear. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.