A Study on the Reduction of Entry Loss by Inner Structure in Square Hood in Industrial Ventilation System

산업환기시설에서 사각형 후드의 내부 설치에 의한 유입손실 감소에 관한 연구

  • Bae, Hyun-Joo (Department of Environmental Health, Graduate School of Public Health, Seoul National University) ;
  • Yang, Won-Ho (Department of Occupational Health, Catholic University of Daegu) ;
  • Kim, Jong-Oh (Department of Environmental Sanitation, Dongnam Health College) ;
  • Son, Bu-Soon (Department of Environmental Health Science, Soonchunhyang University)
  • 배현주 (서울대학교 보건대학원) ;
  • 양원호 (대구가톨릭대학교 산업보건학과) ;
  • 김종오 (동남보건대학 환경위생학과) ;
  • 손부순 (순천향대학교 환경보건학과)
  • Published : 2003.09.25

Abstract

An objective of local exhaust hood design is to design the hood to operate as efficiently as possible. The greatest loss normally occurs at the entrance to the duct, due to the vena contracta in the throat of the duct. This can be accomplished by minimizing the loss that results from the vena contracta. There have been little studied to be cost-effective approach as installing simple instrument inside the throat of the hood. The aims of this paper were to minimize entry loss using inner square, and to measure the effect of inner square when installed inside hood throat. The results of this study were as follows; First, the magnitude of vena contracta could be considered as the difference between direct measured velocity and calculated velocity, which is from Bernoulli theory. In circle hood, calculated velocity and direct measured velocity were 10.7m/sec and 10.3n/sec, respectively. And the calculated velocity and direct measured velocity in square hood were 7.7m./sec and 6.5m/sec, respectively. Second, effect of inner square by width was carried out. The widths of inner square were L/1(18cm), L/2(9cm), L/3(6cm) and L/6(3cm). In case inner square was installed with 3cm width, the entry of coefficient was 0.93, comparing with 0.85 of entry of coefficient of general hood. Third, effect of inner square by distance from hood inside surface to inner square was carried out. The distances were L/3(6cm), L/6(3cm), L/9(2cm) and L/l8(1cm). In case the distance was 3cm the best efficiency was shown (Ce= 0.93). Fourth, effect of inner square by location from hood entry to duct inside was carried out. The locations of inner square were entry(0cm), L/6(3cm), L/3(6cm), L/2(9cm) and L/l(12cm). In case the location was 0cm, 3cm and 6cm the entry of coefficients were 0.93, 0.92 and 0.90, respectively.

Keywords

References

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