How to assign thermodynamic properties after splitting two phase into gas and liquid

[mad fridgie]

The liquid entering the flash econimiser has a specific heat/energy by flashing of some lquid into vapour, you lower the pressure/temperature of the remaining liquid transfering the heat/energy to the vapour, subcooling the remaining liquid...

You are cooling the liquid by vapourizing, the pressure has dropped, so the liquid is at saturation, hence is not sub cooled.