Heat loss from the vapor phase to surrounding (J h −1) Q L loss Overall number of transfer units for vapor phase q 0Ĭonvection heat transfer rate (J h −1) Q V loss Number of transfer units in vapor phase NTU OV Number of transfer units in liquid phase NTU V Molar mass transfer rate of component i at the interface (kmol h −1) NTU L Molar mass transfer rate of component i across the interface (kmol h −1) N i0 Total molar mass transfer rate across the interface (=∑ N i) (kmol h −1) N a Logarithmic Mean Temperature Difference K m: Molar superficial liquid phase velocity (kmol s −1) L jįlow rate of liquid phase leaving the j-th stage or section (kmol h −1) LMTD: Thermal conductivity (of fluid) (J h −1 m −1 K −1) K:Īverage finite-rate mass transfer coefficient (kmol s −1) k avĪverage low-rate mass transfer coefficient (kmol s −1) L: Partial molar enthalpy of component i (J kmol −1) k: It is highly emphasized that estimating efficiency of an operating column has to be distinguished from that of a column being designed.Ĭalculate \(\) For the efficiency calculation, the method employs the column data and uses the true rates of the mass and heat transfers occurring inside the operating column. The method can be used for the efficiency prediction of any trays in distillation columns. E.g., the method does not need to estimate tray interfacial area, which can be its most important advantage over all the available methods. This method can calculate efficiency as well as mass and heat transfer coefficients without using any empirical mass transfer or hydraulic correlations and without the need to estimate operational or hydraulic parameters of the column. In this paper, an applicable and accurate method was developed for the efficiency estimation of distillation columns filled with trays. Therefore, these methods may not be sufficiently accurate when applied to industrial columns. Most of the available methods are based on empirical mass transfer and hydraulic relations correlated to laboratory data. Developing general methods that rely on column data for the efficiency estimation of operating (existing) distillation columns has been overlooked in the literature.