• Title/Summary/Keyword: Dry type heat exchanger

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A Study on the Characteristics of Pressure Distribution for Heat Exchanger Types of Domestic Gas Boiler (가정용 가스보일러 열교환기 유형에 따른 압력분포특성에 관한 연구)

  • 최경석;오율권;차경옥
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.22-28
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    • 2001
  • Heat transfer and pressure distribution for heat exchanger type of domestic gas boiler are different from shape, pitch, thickness of fin and array of pipe respectively. In order to measure the pressure distribution across the heat exchanger, a suction type wind tunnel was constructed and velocity distribution was measured for pilot tube(4 point) of rack type. The experiments were performed for 5 different air flow mass, rpm=3,6,9,12,15 and transverse axis of heat exchanger(x-length) is 5cm respectively. Results showed that above 9.5m/s, pressure distribution dispersion for wet type of heat exchanger is on the increase and above 5.5m/s, pressure distribution dispersion for dry type of heat exchanger is on the increase. Also, pressure distribution dispersion by comparing two different types heat exchanger, dry type of heat exchanger showed a higher augmentation than wet type of heat exchanger.

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A Numerical Study on the Performance Analysis of Plume Abatement Cooling Tower with Dry Type Heat Exchanger (건식 열교환기를 이용한 백연방지 냉각탑 성능의 수치해석적 연구)

  • 김병조;최영기
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.12
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    • pp.1018-1027
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    • 2003
  • This study treats the analysis of the performance and the design of plume abatement wet/dry cooling tower with dry type heat exchanger using a numerical method. A two-dimensional analysis is performed using the finite volume method for mechanical draft counterflow and crossflow tower. For a coupling problem between water and air system, a turbulent two phase flow is considered. Effectiveness-NTU method is used for modeling of the dry type heat exchanger. The parameter change simulations of the outer wall shape, the relative flowrate of air, and attachment of an air mixer are performed to examine the effect on plume abatement. It is found that if the relative air flowrate ratio and the adequate air mixer type are chosen well in addition to the ratio of water to air flowrate, the loss of the cooling capacity and the additional cost are reduced and the plume is abated.

Numerical Study on the Performance Analysis of Plume Abatement Cooling Tower with Dry Type Heat Exchanger

  • Kim, Byung-Jo;Choi, Young-Ki
    • International Journal of Air-Conditioning and Refrigeration
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    • v.13 no.2
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    • pp.61-70
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    • 2005
  • This study treats the numerical analysis of performance and design for plume abatement wet/dry cooling tower with a dry type heat exchanger. A two-dimensional analysis is performed using the finite volume method for mechanical draft counterflow and crossflow tower. For a coupling problem between water and air system, a turbulent two phase flow is considered. The Effectiveness-NTU method is used for modeling of the dry type heat exchanger. The parametric simulations such as the relative flowrate of air and attachment length of an air mixer are performed to examine the effect on plume abatement. It is found that if the relative air flowrate ratio and the adequate air mixer type are chosen well in addition to the ratio of water to air flowrate, the loss of cooling capacity and the additional cost are reduced and the plume is abated.

Performance Evaluation of Air-to-Air Total Heat Transfer with Rotating Porous Plates (다공의 전열판이 내장된 공기 대 공기 전열교환기의 성능 평가)

  • Lim, T.W.;Cho, D.H.
    • Journal of Power System Engineering
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    • v.11 no.2
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    • pp.20-25
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    • 2007
  • The performance of air-to-air heat exchanger has been investigated with rotating porous plates newly developed in this study. With an equal interval of 18 mm, the rotating porous plates are installed inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. Dry bulb temperature is set by adjusting heat supply at heater. In order to measure the temperature distribution of the hot air side inside heat exchanger, the thermocouples are inserted between the plates. The first location of thermocouple is 10mm downstream from the inlet of heat exchanger, and succeeding ten locations are aligned at an equal interval of 18mm. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat transfer rate increased as both air flow rate and RPM of the rotating porous plate increased. It was found that the overall heat transfer coefficient increased with the increase in RPM of porous plate at the conditions of the same air flow rate.

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Analysis on Wetting Behavior of A Lamellar Type Wet Channels in An Evaporative Heat Exchanger (층상구조를 가진 증발식 열교환기 습채널의 표면 젖음도 해석)

  • Oh, Dong-Wook;Park, Jae Bum;Song, Chan Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.7
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    • pp.283-287
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    • 2016
  • One of the most important factors for determining the thermal performance of an evaporative cooling system is the wettability of the evaporative heat exchanger surface. Evaporation of a widely spread water film on the heat exchanger surface promotes heat transfer between the "dry" air and "wet" air passages. Hydrophilic coating is generally applied on the heat exchanger surfaces to increase the wettability of the heat exchanger surface and the COP of the evaporative cooling system. In this paper, a simple lamellar patterned structure is suggested to maximize the spreading of a water film on the vertically oriented walls. The capillary height of the lamellar structured grooves is analyzed through a theoretical model, and the results are compared with the numerical analysis through a finite element analysis tool, SE-FIT. A good agreement between the theoretical model and the numerical analysis can be observed as long as the channel depth is comparable to or larger than the channel width of the lamellar structure.

Effect of Soil Thermal Conductivity and Moisture Content on Design Length of Horizontal Ground Heat Exchanger (토양 열전도도와 수분함량이 수평형 지중열교환기 설계 길이에 미치는 영향)

  • Sohn, Byong-Hu
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.8 no.1
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    • pp.21-31
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    • 2012
  • This paper reviewed and evaluated some of the commonly used prediction models for thermal conductivity of soils with the experimental data. Semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry state soils. It came out that the model developed by Cote and Konrad gave the best overall prediction results for unsaturated soils available in the literature. However, it still needs to be improved to cover a wider range of soil types and degrees of saturation. In the present study, parametric analysis is also conducted to investigate the effect of soil type and moisture content on the horizontal ground heat exchanger design. The analysis shows that horizontal ground heat exchanger pipe length is reduced with the increase of soil thermal conductivity and water content. The calculation results also show that horizontal ground heat exchanger size can be reduced to a certain extent by using backfilling material with a higher thermal conductivity of solid particles.

Evaluation of Conventional Prediction Model for Soil Thermal Conductivity to Design Horizontal Ground Heat Exchanger (수평형 지중열교환기 설계를 위한 토양 열전도도 예측 모델 평가)

  • Sohn, Byong-Hu;Wi, Ji-Hae;Han, Eun-Seon;Lim, Jee-Hee;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.813-824
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    • 2010
  • Thermal conductivity of soils is one of the most important parameters to design horizontal ground heat exchangers. It is well known that the thermal conductivity of soil is strongly influenced by its density and water content because of soil's particulate structure. This paper reviewed and evaluated some of the commonly used prediction models for thermal conductivity of soils with the experimental data available in the literature. Semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry state sands. It came out that the model developed by Cote and Konrad gave the best overall prediction for unsaturated sands available in the literature. Also, a parametric analysis is conducted to investigate the effect of thermal conductivity and water content, soil type on the horizontal ground heat exchanger design. The analysis shows that a required pipe length for the horizontal ground heat exchanger is reduced with the increase of soil thermal conductivity and water content. The calculation results also show that the dimension of the horizontal ground heat exchanger can be reduced to a certain extent by using backfilling material with a higher thermal conductivity of solid particles.

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Comparison of Heat Transfer Performance and Pressure Drop of Fin-Tube and Aluminum Heat Exchangers (핀-튜브 열교환기와 알루미늄 열교환기의 전열성능과 압력강하 특성비교)

  • Chang, Keun-Sun;Lee, Hyun-Su;Kim, Jae-Duck
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.2
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    • pp.222-229
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    • 2009
  • This study presents comparison of heat transfer and air side friction characteristics in a condenser condition of air conditioner between Louver fin-tube heat exchangers and aluminum parallel heat exchangers. All experiments are performed using an air-enthalpy type calorimeter, which is designed based on the method described in ASHRAE standards. The air velocities crossing the heat exchanger tubes are varied from 0.7 to 1.6 m/s with 0.3 m/s interval, maintaining air dry temperature and relative humidity at $20^{\circ}C$ and 60% respectively. Water temperature and flow rate inside the tube are $70^{\circ}C$ and 10 LPM, respectively. Experimental results show that the heat transfer performances of aluminum heat exchangers are 17-163% higher than those of Louver fin-tube heat exchangers based on the data per unit volume, mass, and heat transfer area, whereas air side pressure drops of aluminum heat exchangers are 19-81% lower.

Effects on Refrigerant Maldistribution on the Performance of Evaporator (냉매의 불균일한 분배가 증발기의 성능에 미치는 영향)

  • 김창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.3
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    • pp.230-240
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    • 2004
  • An experimental investigation was conducted to study two-phase flow distribution in a T-type distributor of slit fin-and-tube heat exchanger using R22. A comparison was made between the predictions by previously proposed tube-by-tube method and experimental data for the heat transfer rate of evaporator. Experiments were carried out under the conditions of saturation temperature of 5$^{\circ}C$ and mass flow rate varying from 0.6 to 1.2kg/min. The inlet air has dry bulb temperature of 27$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.63 to 1.71㎧. Experiment show that air velocity increased by 85.2% is need for T-type distributor with four outlet branches than that of two outlet branches under the superheat of 5$^{\circ}C$, which resulted in air-side pressure drop increase of 130% for T-type distributor with four outlet branches as compared to two outlet branches.

Development of a Commercial-scale RDF Boiler with Chain type Stoker (실증규모 체인스토커식 RDF전용보일러 개발)

  • Choi, Yeon-Seok;Kim, Byung-Gil;Roh, Nam-Sun
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.813-816
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    • 2009
  • A commercial-scale RDF boiler that its burning capacity is 400 kg-RDF/hr and steam production capacity is 2 ton/hr. It has a chain type stoker and waste heat recovery system. Heat exchanger is vertical water-pipe so that soot blowing and removal is convenient during operation. Dry scrubber, bag filter and activated carbon tower have been installed for the reduction of air pollutant gases and dust. Analysing data of pollutants from stack such as $SO_x$. $NO_x$ and dioxin shows so good results that the boiler system could comply the regulated emission limits.

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