• 제목/요약/키워드: Air conditioning units

검색결과 123건 처리시간 0.023초

산업시설 배관 노후도 평가를 위한 배관 섹션화 방안 연구 (A Study of the Sectionalizing for Pipe Deterioration Evaluation in Industrial Facilities)

  • 민혁기;김상범;김병우;김형기;박률
    • 설비공학논문집
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    • 제27권2호
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    • pp.103-111
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    • 2015
  • In general, no particularly well-established standards have been in place so far, for the method of evaluating the deteriorated level of pipes and ducts of industrial facilities. For that reason, the evaluation depends upon various studies which are based on the analysis of the residual life, thickness thinning, closure rate, and scale thickness that measure a few specific positions of pipes. It also depends upon the expertise in business operation and the specific techniques conducted by the inspection companies and institutions. This research introduces the concept of measuring units per section and the selection method of measurement points per section. Furthermore, specific methodologies were developed to plan and analyze deterioration level of industrial pipes and ducts by engineers and managers using a section map. Consequently, applying the outcomes from this study to the plant equipment of the incineration facility resulted in saving 42% of the repairing and remodeling cost.

성능선도에 의한 다통로 판형열교환기의 간이설계법 (An easy-to-use design procedure for multipass plate heat exchangers based on the performance plots)

  • 유호선;이근휘;방보청
    • 설비공학논문집
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    • 제11권2호
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    • pp.250-261
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    • 1999
  • Based on a set of performance plots relating the design variables to the imposed conditions, an easy-to-use and versatile design procedure for chevron-type multipass plate heat exchangers is developed. In order for the present procedure to cover multipass with unequal passes and non-unity ratio of heat capacity rate, each stream number of transfer unit is adopted as the basic design variable instead of the exchanger number of transfer unit. It is found that there exists a unique relation between the stream and exchanger number of transfer units regardless of the chevron angle and the plate length. In addition, for a given value of the pressure drop the heat transfer area per unit mass flow rate can be expressed in terms of the stream number of transfer unit only. These two relationships in the form of simple plots constitute the framework of design. The sample results in comparison with the available data indicate that the present procedure includes the previous ones as a subset, and that every design method is affected essentially by the selection of specific correlations for the heat transfer coefficient and the friction factor.

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모세관을 이용한 멀티형 열펌프의 신뢰성에 관한 실험적 연구 (An Experimental Stuff on the Performance of Multi-type Heat Pump using Capillary Tubes)

  • 권영철;장근선;이윤수;김대훈;전용호;이상재
    • 설비공학논문집
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    • 제14권9호
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    • pp.749-755
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    • 2002
  • In order to develop a multi-type heat pump system with two indoor units of non-uniform capacities, the optimum refrigerant circuit was developed using capillary tubes. The refrigerant circuit was composed of four main parts, a heating circuit, a cooling circuit, a by-pass circuit and a balance circuit. The system characteristics of multi-type heat pump was investigated through the rating test and the reliability test, using the multi-type psy-chrometric calorimeter. The results of the rating test showed that the capacity of the multi-type heat pump was about 93% of the design value. In particular, the capacity of cooling single mode was about 13% higher than the design value, and the capacity of heating multi mode was about 5% higher than the design value. The reliability of the multi-type heat pump was verified by various reliability tests (overload, extension tube, freeze up, under/over charging, sweat, flood back). The optimal amount of refrigerant charge and compressor capacity were determined from the present work.

전자팽창밸브 제어성능 모사용 증발기 동특성 모델링 (A Dynamic Simulation Model of Electronic-Expansion-Valve-Controlled Evaporators)

  • 신영기;조수;태춘섭;장철용
    • 설비공학논문집
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    • 제19권2호
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    • pp.183-190
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    • 2007
  • Controlling superheat of indoor units associated with a multi-type heat pump is one of difficult tasks to be addressed. This study suggests a dynamic model of an evaporator based on heat and mass balance. Thermodynamic properties are calculated by a commercial software, Refprop. The model is programmed in MFC Visual C++ for controller interface in real-time mode. The simulation results shows that PI control works for a narrow range of superheat. Beyond the range, the temperature behavior of the refrigerant is quite nonlinear mainly due to phase change. Thus, it is concluded that PI control of superheat has to be supplemented by nonlinear control ideas to avoid saturation and excessive superheat.

폐열회수용 핀-튜브 열교환기 성능 수치모사 (Numerical Simulation of a Fin-Tube Heat Exchanger for Waste Gas Heat Recovery)

  • 남명환;맹재훈;구병수;전용두;이금배
    • 설비공학논문집
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    • 제23권2호
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    • pp.120-125
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    • 2011
  • As an effort to secure economically viable heat recovery units, innovative fin shapes for industrial boilers are studied for better performance. In the present study a numerical modeling for the analysis of heat exchanger performance is conducted using a commercial software, ANSYS CFX and the results are compared with the experimental data. Out of several candidate fin shapes curved wavy fin is selected for the present study. Both numerical and experimental data are directly compared for heat transfer rate and pressure drop with the assumed constant surface temperature of $60^{\circ}C$. Exhaust gas is obtained from a test apparatus which supplies variable flow rates. The numerical results show reasonable agreements with the experimental data within 10% in terms of both total heat transfer and pressure loss.

타원관 열교환기를 적용한 팬코일 성능 시험 (Performance Test of a Fan Coil with an Oval-Type Heat Exchanger)

  • 윤재동;이승현;성재용;이명호
    • 설비공학논문집
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    • 제26권2호
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    • pp.67-71
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    • 2014
  • In this study, a fan coil unit with an oval-type heat exchanger has been developed. The performance of the present fan coil unit has been investigated, by comparison with the previous fan coil unit with a circular-type heat exchanger. For the fan coil unit with circular- and oval-type heat exchangers, the heat flux and pressure loss through the heat exchangers were measured at standard operating conditions. In addition, the wind speeds exhausted from the fan coil units were compared, for the same fan motor operation. The experimental results show that the average wind speed of the oval-type heat exchanger is 20 percent higher than that of the circular-type heat exchanger. The heat flux in the oval-type heat exchanger is enhanced by 40% or more, over the circular-type heat exchanger.

냉방주체 운전모드에서 동시냉난방 열펌프 성능향상에 관한 실험적 연구 (Experimental Study on the Performance Improvement of a Simultaneous Heating and Cooling Heat Pump in the Cooling-main Operating Mode)

  • 정현준;주영주;강훈;김용찬;최종민
    • 설비공학논문집
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    • 제20권5호
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    • pp.314-320
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    • 2008
  • The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the improved wall insulation. Hence, a multi~heat pump is required to cover heating and cooling simultaneously for each indoor unit. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-main operating mode were investigated experimentally. The system adopted a variable speed compressor using R410A with four indoor units and one outdoor unit. In the cooling-main mode, the heating capacity decreased due to reduction of flow rate to the indoor unit under heating mode operation. The EEV opening was adjusted to increase flow rate to the indoor unit under heating mode operation. The total capacity and COP in the cooling-main mode increased by 20.5% and 29.2%, respectively, compared with those in the cooling-only mode.

응축형 가스보일러시스템의 제어 알고리즘 개발을 위한 효과적인 동적모델 (Effective Dynamic Models for the Development of Control Algorithms of a Condensing Gas Boiler System)

  • 한도영;김성학
    • 설비공학논문집
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    • 제20권6호
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    • pp.365-371
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    • 2008
  • Condensing gas boiler units may make a big role for the reduction of energy consumption in heating industries. In order to decrease the energy consumption of a condensing gas boiler unit, effective operations of the system are necessary. In this study, mathematical models of a condensing gas boiler system were developed in order to develop control algorithms of the system. These include dynamic models of a blower, a gas valve, a pump, a burner, a boiler heat exchanger, and a hot water heat exchanger. Control algorithms of a blower, a gas valve, and a pump were also assumed. Simulation results showed good predictions of dynamic behaviors of a boiler system. Therefore, the simulation program developed for this study may be effectively used for the development of control algorithms of a boiler system.

GHP 난방 모드 운전시 실시간 부하 추정방법에 관한 연구 (A Study on Estimating Real-time Thermal Load During GHP Operation in Heating Mode)

  • 서정아;신영기;오세제;정상덕;지경철;정진희
    • 설비공학논문집
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    • 제23권1호
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    • pp.32-37
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    • 2011
  • The present study has been conducted to propose an algorithm regarding real-time load estimation of a gas engine-driven heat pump. In the study, thermal load of an indoor unit is estimated in terms of air-side and refrigerant-side. The air-side estimation is based on a typical heat exchanger model and is found to be in good agreement with experimental data. When it comes to the refrigerant-side load, a pressure difference across a valve must be estimated. For the estimation, it is assumed to be proportional to a bigger pressure difference that is available either by measurement or by estimation. Relative good agreement between the air- and refrigerant-sides suggests that the assumption may be plausible for the load estimation. The summed flow rate of all of indoor units is in good agreement with the throughput of the compressor which are calculated from the manufacturer's software. Accordingly, estimated thermal loads are also in good agreement. The proposed algorithm may be further developed for improved control algorithm and fault diagnosis.

급·배기 일체형 디퓨저의 환기 및 온열환경 유지성능에 대한 연구 (A Study on The Performance of Ventilation and Maintaining Thermal Environment for a Combined Type Diffuser)

  • 임석영;장현재
    • 설비공학논문집
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    • 제28권6호
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    • pp.232-241
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    • 2016
  • Installing a ventilator for an apartment house composed of over 100 dwelling units was mandated in 2006 to improve indoor air quality. In the case of mechanical ventilators, the air change rate is kept stable, however 68% of dwellers do not operate their ventilator because of an increased electrical bill and noise. In the case of natural ventilators, the former problems are settled, but there are concerns about cold draught and an increase of heating/cooling cost. Authors are developing a heat recovery type natural ventilator which is a natural ventilator equipped with total heat recovery element, and it is expected that those problems of mechanical ventilator and natural ventilator are resolved by this. The combined type diffuser of this study is an under developed fit to the heat recovery type natural ventilator above. There are no standards to evaluate the performance for this type of diffuser. Due to this issue this study investigated the performance of the ventilation and maintained a thermal environment for the combined type diffuser by comparing it with existing diffusers. The results revealed that the performances of the combined type of diffusers showed different features from the existing ones, and was estimated to be high enough in the performances above.