Fluid flow and temperature change

[BillNye]

I know there is a way but I can't seem to remember the equation for temperature change in a flow. Like if I have water that is 30 C with a rate of 30 liters per minute and another flow of water at 40C with a rate of 10 liters per minute, how could I calculate the final temperature of the mixture? I know there is an equation for this but I can't seem to remember. Anyone have any suggestions?

 

Thank you.

[timo]

I'm not aware of a well-known equation for it, but I can offer an approximate solution: First, assume the volume of water in one second for simplicity (the second will drop out of the calculation, soon). Then, calculate the thermal energy that each of the flows brings in (approximated by heat capacity times temperature times amount of water). Add up the energies. You now have the total energy of the two water masses combined. You can get the resulting temperature by using the heat capacity again.

Edited June 24, 2013 by timo