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A Decoupling Method to Compute Near Field and Far Field Exposure Concentrations



Details

  • Personal Author:
    Nicas M
  • Description:
    In the near field/far field (NF/FF) dispersion construct, the analytical solutions for the NF and FF concentration equations, respectively denoted CNF(t) and CFF(t) in mg/m3, are coupled in their mathematical derivation. Depending on the form of the contaminant emission rate function G(t) (mg/min), deriving CNF(t) and CFF(t) can range from being relatively easy to impossible. A method is presented to more easily approximate these concentration functions. The method decouples the NF and FF equations by treating the NF as an isolated well-mixed space with volume VNF (m3) and supply/exhaust airflow rate β(m3) and treating the FF as an isolated well mixed-space with volume V (m3) and supply/exhaust airflow rate Q (m3). Assuming that each space contains a source with the same contaminant emission rate function G(t), a contaminant concentration function is derived for the FF zone, denoted CWMR1(t), and an independent contaminant concentration function is derived for the NF zone, denoted CWMR2(t). Deriving a concentration function for a single zone is far easier than deriving coupled concentration functions. It is shown that the sum CWMR1(t) + CWMR2(t) provides an excellent approximation of CNF(t) and that CWMR1(t) provides an excellent approximation of CFF(t). A discrete-time numerical solution for the CNF(t) and CFF(t) system based on a Markov matrix is also presented. [Description provided by NIOSH]
  • Subjects:
  • Keywords:
  • ISSN:
    2398-7308
  • Document Type:
    Text
  • Funding:
    Grant
  • Genre:
    Journal Article
  • Place as Subject:
  • CIO:
    National Institute for Occupational Safety and Health (NIOSH)
  • Topic:
    Workplace Safety & Health
  • Location:
    North America
  • Pages in Document:
    78-85
  • Volume:
    68
  • Issue:
    1
  • NIOSHTIC Number:
    nn:20069744
  • Citation:
    Ann Work Expo Health 2024 Jan; 68(1):78-85
  • Contact Point Address:
    Mark Nicas, School of Public Health, Environmental Health Sciences Division, 2121 Berkeley Way, University of California, Berkeley, CA 94740-7360, USA
  • Email:
    mnicas@berkeley.edu
  • Federal Fiscal Year:
    2024
  • Performing Organization:
    University of California, Berkeley
  • Peer Reviewed:
    True
  • Start Date:
    20050701
  • Source Full Name:
    Annals of Work Exposures and Health
  • End Date:
    20250630
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:68a59a37e1fd91a5e3698c1c9844f3a7c2f9188b69c8e34729ca1d59f712f9d1bee34b0741c3b625949f9638e92399f2dd018553271319207a6e4bafaddbbaae
  • Download URL:
  • File Type:
    Filetype[PDF - 2.17 MB ]
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