Default heat capacity values

A discussion forum for users of the new HYDRUS 2D/3D. HYDRUS is a software package for simulating water, heat and solute movement in two- and three-dimensional variably saturated media. Happy Posting!
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jimboonman
Posts: 8
Joined: Mon May 04, 2020 9:20 am
Location: Netherlands

Default heat capacity values

Post by jimboonman » Tue Mar 23, 2021 11:19 am

Dear Jirka,

I noticed that the values Co, Cw and Cn, unlike other default parameters for heat transport, are not changed according to the project time unit. I'm using version 3.02. Maybe this could be improved in future updates of the program.

The values I calculated for Cn, Co and Cw with length unit [meter] and time unit [days] are 1.43e+016, 1.87e+016 and 3.12e+016 respectively.


Best regards,
Jim

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Default heat capacity values

Post by Jirka » Tue Mar 23, 2021 6:40 pm

Are you sure about this? I have just tested version 3.02.0630, which is installed on my desktop, and everything with respect to conversions of heat transport parameters seems to be working fine. I opened the Test1 example, added heat transport, checked the heat transport parameters, changed the units from s to d, and checked the heat transport parameters again. They were all converted correctly. Do you want to send us your project? J.

jimboonman
Posts: 8
Joined: Mon May 04, 2020 9:20 am
Location: Netherlands

Re: Default heat capacity values

Post by jimboonman » Wed Mar 24, 2021 3:17 pm

Dear Jirka,

I just created a new project in HYDRUS 3.02.0690 in length and time units [m] and [day], and added heat transport. Now I get the correct values.
However, within the projects I’ve been working with for over a year now, I found different values for heat capacity: 1.92e+006, 2.51e+006, 4.18e+006 for [m] and [days]. When changing the back to seconds and then to days , I still did not get correct values. So it seems that I have defined the values myself in an early stage, when I was not considering the correct SI unit-conversion. Furthermore, I mis-interpreted the “Set default Volumetric Heat Capacities”-button as if the program would restore the default Cn, Co and Cw values, which is not the case.

Although I acknowledge my mistake (my apologies), I would think that restoring default values of Cn, Co and Cw with the “Set default Volumetric Heat Capacities”-button would be an improvement in further versions!


Best,
Jim

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Default heat capacity values

Post by Jirka » Wed Mar 24, 2021 4:08 pm

Thanks for your comments. Since we are always tinkering with the software (trying to improve it) there is always a chance that we will introduce some new bugs, and thus, it is always good to check and re-check, and test, etc. We do partly rely on our users to help us with that and report any problems.

The default heat capacity should always be set according to eq. 4.2 of the technical manual, i.e., Cn=1.92*10^6, Co=2.51*10^6, and Cw=4.18*10^6 J/M3/C [kg/m/s2/K].

J.

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