- #1
bumblebee77
- 56
- 2
Hi everyone:
I am not really a thermo person, but need to use thermo data in some other calculations. I have enthalpy, heat capacity, temperature, and density, as well as other data.
I can't calculate/reproduce the enthalpy data using the other parameters and would really appreciate some clues as to where I'm going wrong (because I need to know if I should use the enthalpy data or the other data in my new calculations, or if there's some other problem). My understanding is that dH/dT=Cp. The data table is attached.
The thermo data are from multiphase solidification calculations. Could it be that for phase change, the equation above doesn't account for latent heat? If this is the case, then my problem is solved and I will use the enthalpy values in my new calculations.
Here's another question. Sorry--it is probably really basic. The enthalpy values from this solidification calculation are all negative. Is this OK? I mean, can I use these negative values in my other transport calculations? My understanding is that a system can be defined so that enthalpy is positive or negative. But if I remove the negative, then the values decrease with increasing temperature and this can't be right. Can someone point me in the right direction for resolving this? I may not have explained myself very well here. Thanks a lot.
I am not really a thermo person, but need to use thermo data in some other calculations. I have enthalpy, heat capacity, temperature, and density, as well as other data.
I can't calculate/reproduce the enthalpy data using the other parameters and would really appreciate some clues as to where I'm going wrong (because I need to know if I should use the enthalpy data or the other data in my new calculations, or if there's some other problem). My understanding is that dH/dT=Cp. The data table is attached.
The thermo data are from multiphase solidification calculations. Could it be that for phase change, the equation above doesn't account for latent heat? If this is the case, then my problem is solved and I will use the enthalpy values in my new calculations.
Here's another question. Sorry--it is probably really basic. The enthalpy values from this solidification calculation are all negative. Is this OK? I mean, can I use these negative values in my other transport calculations? My understanding is that a system can be defined so that enthalpy is positive or negative. But if I remove the negative, then the values decrease with increasing temperature and this can't be right. Can someone point me in the right direction for resolving this? I may not have explained myself very well here. Thanks a lot.