vanillabeans12
Chemical
- Mar 10, 2024
- 4
Hello,
I'm trying to estimate the time it takes to heat a solution in a closed tank vessel with direct steam injection. You can think of it as a tank with a mass of solution in it, and steam is injected with spargers.
The overall energy balance is :
dE/dt = mass in (hin + vin + pin) - massout (hout - vout - pout) + Q + Ws
No steam is being stripped overhead, the steam condenses and adds weight to the solution, nothing else is coming out, so mass out is removed. Heat is being done through the enthalpy of mass, not convection, so Q is out. I'm assuming shaft work heat is negligible, so Ws is out. And there's no potential/kinetic energies going in that I should be worried about. I know I can say energy (dE) can be enthalpy (dh) so that h=m*cp*dT (cp is specific heat capacity, dT is change in temperature).
so that dh/dt = mass in (hin) or mass of solution *cp*dT/dt = mass of steam in *(hin)
and integrate to get:
(Tfinal - Tiniital) = mass of steam in *hin/mass of solution * cp
My question is for hin. That is the enthalpy of the steam going into the tank. Do I use absolute value of the latent heat of the steam based on its pressure? So if it's 20 psi, it would be 2184kJ/kg?
I'm trying to estimate the time it takes to heat a solution in a closed tank vessel with direct steam injection. You can think of it as a tank with a mass of solution in it, and steam is injected with spargers.
The overall energy balance is :
dE/dt = mass in (hin + vin + pin) - massout (hout - vout - pout) + Q + Ws
No steam is being stripped overhead, the steam condenses and adds weight to the solution, nothing else is coming out, so mass out is removed. Heat is being done through the enthalpy of mass, not convection, so Q is out. I'm assuming shaft work heat is negligible, so Ws is out. And there's no potential/kinetic energies going in that I should be worried about. I know I can say energy (dE) can be enthalpy (dh) so that h=m*cp*dT (cp is specific heat capacity, dT is change in temperature).
so that dh/dt = mass in (hin) or mass of solution *cp*dT/dt = mass of steam in *(hin)
and integrate to get:
(Tfinal - Tiniital) = mass of steam in *hin/mass of solution * cp
My question is for hin. That is the enthalpy of the steam going into the tank. Do I use absolute value of the latent heat of the steam based on its pressure? So if it's 20 psi, it would be 2184kJ/kg?
