calculating temperature during mixing

[jlh06]

I am running a mixing simulation in React between hydrothermal fluid (350C) and seawater (2C) and am wondering how GWB determines temperature. I mix 1000 parts seawater into 1 part hydrothermal fluid and get to 5C - this is good. It appears that temperature changes linearly with mixing. Does React account for the nonlinear dependence of temperature on heat at high temperatures as density changes? I do not see anywhere in the database or the output that it keeps track of heat capacity or enthalpy, although I see that it tracks density of the mixed fluid.

 

Thanks for your help.

[Brian Farrell]

Hi, from the GWB Reaction Modeling Guide, Release 8.0:

 

Polythermal Reaction Paths:

"In a polythermal mixing model, you set temperatures for the reactants and the initial system. Over the path, the program calculates temperature from the mass of reactant that has been added to the system, using the approximate heat capacities for fluids and minerals stored in variables cpw and cpr (on the Config - Variables dialog)."

 

So basically you set a heat capacity for the fluid (default 1 cal/g/C) and "rock" (default 0.2 cal/g/C) which is used throughout the calculation. Because the mass of the fluid (water plus solutes) is what goes into the calculation, density is not important.

 

Hope this helps,

Brian