code: def chung(target, temperature='pore.temperature',
            mol_weight='pore.molecular_weight',
            critical_temperature='pore.critical_temperature',
            critical_volume='pore.critical_volume'):
      r
      T = target[temperature]
      MW = target[mol_weight]
      Tc = target[critical_temperature]
      Vc = target[critical_volume]
      Tr = T / Tc
      Tstar = 1.2593*Tr
      A = 1.161415
      B = 0.14874
      C = 0.52487
      D = 0.77320
      E = 2.16178
      F = 2.43787
      omega = (A*(Tstar)**(-B)) + C*(sp.exp(-D*Tstar)) + E*(sp.exp(-F*Tstar))
      sigma = 0.809*(Vc**(1/3))
      value = 26.69E-9*sp.sqrt(MW*T)/(omega*sigma**2)
      return value
docs: r"""
      Uses Chung et al. [1] model to estimate viscosity for gases at low
      pressure (much less than the critical pressure) at conditions of interest.
  
      Parameters
      ----------
      target : OpenPNM Object
          The object for which these values are being calculated.  This
          controls the length of the calculated array, and also provides
          access to other necessary thermofluid properties.
  
      temperatre: string
          The dictionary key containing the temperature values (K)
  
      critical_temperature : string
          The dictionary key containing the temperature values (K)
  
      mol_weight: string
          The dictionary key containing the molecular weight values (kg/mol)
  
      critical_volume : string
          The dictionary key containing the critical volume values (m3/kmol)
  
      [1] Chung, T.H., Lee, L.L., and Starling, K.E., Applications of Kinetic Gas
          Theories and Multiparameter Correlation for Prediction of Dilute Gas
          Viscosity and Thermal Conductivity”, Ind. Eng. Chem. Fundam.23:8, 1984.