• 제목/요약/키워드: type of heat exchanger

검색결과 565건 처리시간 0.024초

고분자 첨가제에 의한 OTEC용 판형 열교환기의 마찰저항감소 효과 연구 (Effect of Polymer Additives on Drag Reduction for a Plate Type Heat Exchanger in OTEC Applications)

  • 김능수;윤석만;서태범;김종보
    • 태양에너지
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    • 제19권2호
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    • pp.37-44
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    • 1999
  • Experimental investigation has been carried out to determine drag reducing effects of polymer additives for a plate type heat exchanger(evaporator or condenser) in OTEC power plant applications, where the pressure drop in the heat exchangers takes up $70{\sim}80%$ of the total pumping power in the existing system. The rate of drag reduction was investigated with various polymer concentrations and mass flow rates. Experiments were undertaken for a test section in Alfa-Laval plate heat exchanger utilizing Poly Ethylene Oxide(Mw $5{\times}10^6$) as polymer additives. Concentrations of polymer additives were 5, 10, 20, 30, 40, 50, 100, 200, 400 wppm at $25^{\circ}C$ and mass flow rates were 0.6kg/s, 0.7kg/s, 0.8kg/s and 0.9kg/s in normal operating ranges for a 15kW Alfa-Laval plate heat exchanger. The maximum effects of drag reductions were found at approximately 0.7kg/s of mass flow rate. The results show that there exists the optimum mass flow rate for the plate heat exchanger to obtain maximum drag reductions. Drag reduction of 20% means considerable savings in pumping power for a large size of OTEC plant.

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Design of air-cooled waste heat removal system with string type direct contact heat exchanger and investigation of oil film instability

  • Moon, Jangsik;Jeong, Yong Hoon;Addad, Yacine
    • Nuclear Engineering and Technology
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    • 제52권4호
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    • pp.734-741
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    • 2020
  • A new air-cooled waste heat removal system with a direct contact heat exchanger was designed for SMRs requiring 200 MW of waste heat removal. Conventional air-cooled systems use fin structure causing high thermal resistance; therefore, a large cooling tower is required. The new design replaces the fin structure with a vertical string type direct contact heat exchanger which has the most effective performance among tested heat exchangers in a previous study. The design results showed that the new system requires a cooling tower 50% smaller than that of the conventional system. However, droplet formation on a falling film along a string caused by Rayleigh-Plateau instability decreases heat removal performance of the new system. Analysis of Rayleigh-Plateau instability considering drag force on the falling film surface was developed. The analysis results showed that the instability can be prevented by providing thick string. The instability is prevented when the string radius exceeds the capillary length of liquid by a factor of 0.257 under stagnant air and 0.260 under 5 m/s air velocity.

열교환기 형식에 따른 열교환기의 에너지 및 엔트랜시 성능 특성 해석 (Energy and Entransy Characteristic Analysis of Heat Exchangers Depending on Heat Exchanger Type)

  • 김경훈;정영관;한철호
    • 한국수소및신에너지학회논문집
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    • 제31권1호
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    • pp.112-121
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    • 2020
  • In this work energy and entransy characteristics of heat exchangers are analyzed for 12 different flow arrangements of heat exchangers. The dimensionless parameters are number of entransy dissipation (Ng), number of entransy dissipation-based thermal resistance (Nr), and entransy dissipation-based effectiveness of heat-exchanger (εg). The dimensionless parameters are expressed analytically in terms of the effectiveness of heat exchanger (ε), heat capacity ratio (c), and number of transfer unit (N) for optimal performance of heat exchangers. Results showed that the dimensionless parameters based on the entransy dissipation can be useful concepts for optimal design of heat exchangers.

자동차 공조용 핀형 열교환기의 성능특성에 관한 연구 (A Study on the Performance Characteristics of Fin-type Heat Exchanger for the Automobile Air-Conditioners)

  • 홍경한;전상신;이승재;박찬수;권일욱;김재열;김병철;하옥남
    • 한국공작기계학회논문집
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    • 제13권4호
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    • pp.100-105
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    • 2004
  • Fin-tube type(Fin-type) heat exchanger has been tested in order to replace the heat exchanger of parallel flow type(P.F -type) which is now widly used in automobile air conditioning system The following conclusions are drawn by the comparison of the characteristics of the heat exchangers. Evaporator and condenser capacities and COP(Coefficience of performance) were varied as with the compressor speed, outdoor air temperature and air flow rate changed, which much influenced on the characteristics of the air conditioning system Evaporator and condenser capacities were increased with increasing compressor speed and outdoor air temperature. Evaporator and condenser pressures of Fin-type were decreased by 7% and 5% respectively compared with those of P.F-type. The COP of Fin-type was decreased with increasing outdoor air temperature and compressor speed. The COP of P.F-type was decreased by 14% compared with that of Fin-type.

자동차 공조용 증발기의 고성능화에 관한 연구 (Study on Development of High Performance Evaporator for Automotive Air Conditioner)

  • 강정길;김기효;박태영;김종수
    • 설비공학논문집
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    • 제7권1호
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    • pp.73-80
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    • 1995
  • The object of the present study is to develop a high performance evaporator for automotive air conditioner. The experiment has been conducted on evaporative heat transfer coefficient inside a plate type heat exchanger with a sharp 180-degree turn flow. The test plates have different formed surface, cross-ribbed channel and elliptical-ribbed channel. Also experimental study has been performed to determine optimal design in elliptical-ribbed plate heat exchanger with different turn clearance. In addition to the above experiments, refrigerant behavior and surface temperature distribution in the plate heat exchanger were observed using color thermoviewer(infrared thermometer). In this experiment, working fluid was used R-12 and test conditions were as follows : (1) saturation pressure of $2.116kg/cm^2$, (2) mass fluxes of 40 to $70kg/m^2s$, (3) heat fluxes of 4,500 to $7,300W/m^2$, (4) inlet quality of 0.1 to 0.7. The results indicated that the evaporative heat transfer coefficient of an elliptical-ribbed plate heat exchanger was higher than that of cross-ribbed plate heat exchanger. Also optimal turn clearance in an elliptical-ribbed plate heat exchanger was determined.

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Tow in 와류발생기에 의한 핀-관 열교환기의 성능실험 (Performance Evaluation in Fin-Tube Heat Exchanger by Tow-In Winglet Pairs)

  • 곽경민;;배철호
    • 설비공학논문집
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    • 제15권2호
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    • pp.87-94
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    • 2003
  • To reduce the air side pressure drop in air-cooled heat exchanger, tow-in type winglet vortex generators are applied. A specially designed multiple-channel test core was used in the experiments for the various geometry of winglet vortex generators. The proposed tow-in type vortex generator gives significant separation delay, reduces form drag, and removes the zone of poor heat transfer from near-wake of the tubes. The results show the significant pressure drop reduction for the tow-in win91e1 vortex generators with the similar enhancement of the heat transfer as other vortex generator applications in heat exchanger. In the range of Reynolds number of 350 to 2100 the pressure drop decrease 8∼15% and 34∼55% for the in-line and staggered tube banks, respectively, compared to those without vortex generators.

수치해석을 통한 저심도 유닛형 지중열교환기의 성능 검토 (Performance Analysis of a Low-Depth Unit-Type Ground Heat Exchanger using Numerical Simulation)

  • 오진환;서장후;남유진
    • 설비공학논문집
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    • 제27권3호
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    • pp.169-173
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    • 2015
  • Recently, ground source heat pump (GSHP) systems have attracted much attention, according to the enhanced social demand of renewable energy. GSHP systems can achieve higher coefficient of performance than the conventional air-source heat pump systems by utilizing stable underground temperature. However, the initial cost of GSHP system is higher than that of the conventional systems, especially, in the small-size buildings. Therefore, it is necessary to develop small-size ground heat exchanger with low cost and quick installation. In this study, a unit-type ground heat exchanger was developed and heat exchange rate was calculated by the numerical simulation. As a result, 27.45 W/m of heat exchange rate was acquired in the condition of $0.5m{\times}0.2m{\times}2m$ unit.

저심도 지중열교환기 개발을 위한 그라우트 재료에 따른 채열성능 검토 연구 (The Performance Analysis for Low-Depth Unit-type Ground Heat Exchanger According to Grouting Materials)

  • 오진환;남유진
    • 한국지열·수열에너지학회논문집
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    • 제11권2호
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    • pp.7-11
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    • 2015
  • Recently, as the demand for sustainable energy sources is increasing, ground-source heat pump (GSHP) systems are receiving growing attention. However, the initial cost of GSHP system is higher than it of the conventional systems, especially, in small-size buildings. Therefore, for the application to the small-size building, it is necessary to develop small-size ground heat exchanger with small-size buildings. In this study, analysis of unit-type heat exchanger due to grouting materials. As a result, 1492.14 W of heat exchange rate was acquired in the condition of cement-silica sand-graphite materials.

관 형태에 따른 Shell and Tube 열교환기의 열전달계수 관한 연구 (Study on Heat Transfer Coefficient Test of Evaporator Tube in Shell and Tube Heat Exchanger by Shape)

  • 김재정;박재홍;김인관;김영수
    • 대한설비공학회:학술대회논문집
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    • 대한설비공학회 2006년도 하계학술발표대회 논문집
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    • pp.1107-1112
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    • 2006
  • The purpose of this study is a heat transfer coefficient test of evaporator tube in shell and tube heat exchanger by shapes, using R-404A. The experimental apparatus is designed to simulate the real heat transfer rate in one shell and tube heat exchanger. The test section is formed four type tubes that are Inner ridged tube, Corrugated tube, Turbo-C tube, Inner fin tube and shell type is formed by electrical heater. All tests were performed at a fixed refrigerant evaporator temperature at $1.5^{\circ}C,\;-3^{\circ}C$ and with mass fluxes of 29, 25 kg/hr. Heat transfer rate is calculated a enthalpy difference in test section. In experiment, heat transfer coefficient measured one by one and electrical heaters are supplemented by evaporator.

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콜로게이트 열교환기와 평판형 열교환기의 열전달특성에 관한 실험적 연구 (Experimental Study on the Heat Transfer Characteristics in Corrugated and Flat Plate Type Heat Exchanger)

  • 박정훈;정용기;전충환;장영준;임혁
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 추계학술대회
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    • pp.37-42
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    • 2003
  • An experiment was performed to study heat transfer characteristics between corrugated heat exchanger and flat plate type one. While heat capacity(13.86kW) was provided constantly and the flow speed was varied from 2.8 to 17.9m/s, The temperature and the pressure drop were measured. Furthermore, Heat transfer coefficient, Colburn factor and Nusselt number were calculated using them. With increase of the flow speed for both exchangers, the coefficient and the pressure drop increased, but Colburn factor decreased. The coefficient, pressure drop and Colburn factor of the corrugated type were all higher than those of the flat one, which is due to the flow interruption with recirculation and reattachment of the corrugated type. The empirical correlations of Nusselt number were suggested for the tested two heat exchangers.

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