where mt, mgs;v , mv denote the mass flow rate of the cold water, the
mass flow rate of the flue gas without steam and the mass flow rate
of the steam, respectively, Cpt and Cpgs,v are the heat specific at constant
pressure of cold water and flue gas without the steam, hs,in and
hTb are the enthalpy value of steam at the temperature of inlet flue
gas and water bath, respectively. The thermo-physical properties of
flue gas outside the tube bundle such as density and thermal conductivity
are calculated at the bulk flue gas temperature (Ts), similarly,
on the tube-side, the bulk temperature of the water (Tt) inside
the tube bundle is used as the reference temperature to determine
water’s properties: