1 reply to this topic

[Manas31]

Hello everyone, I have doubt regarding negative enthalpies. I have to calculate energy loss in a process.

What I know is that there are two input energy streams. One with negative enthalpy and one with positive enthalpy.Lets suppose one is -5000 btu/hr and other is 2000 btu/hr. The output energy stream is at

-1000 btu/hr. So what will be the energy loss here? What I am not able to get here is the input energy should be taken as -3000 btu/hr or 7000 btu/hr or something else.Can somebody explain as for what should be done in such cases?

 

Thanks

  

[latexman]

The sign the enthalpy of a stream only tells you if the stream has more or less energy than the reference conditions.  Do not let that bother you.  The key is the difference in enthalpy of your process.  Just plug the negative numbers into your heat balance, be careful to apply all the sign rules, and you should get the correct change in enthalpy or heat duty required.

Edited by latexman, 17 July 2013 - 11:25 AM.