Assuming you have installed debian package and convrted using deb (dwsim version 6.2.2)

Make sure this dependencies are satisfied

check the process below for  reinstalling 

• Allow the installer, pacman, to access the AUR repository (not as default)

•  from AUR install the following packages:

• - debtap (ver3.2.2-1)

• - mono-basic (ver 4.8-1) not mono only! The name is misleading because mono-basic is not a reduced version of mono but a package with mono and VBbasic

• - gtk-sharp-2 (ver2.12.45-2)

•  download from sourceforge: dwsim_6.2.2-amd64.deb

•  open a terminal and transform the deb package to a arch package with debtap: $ debtap dwsim_6.2.2-amd64.deb

• answer to the questions such name (i.e. dwsim-6.2.2amd64) licence (i.e. GPL2) and when it asks to open a .PKGINFO answer with choice 2 (nano editor is preinstalled in Manjaro).

•  change : gtk>=2.12 in gtk2>=2.12 because Manjaro has gtk2 preinstalled, save and exit

• at the and debtap gives you a compress package called:dwsim-6.2.-2-x86_64.pkg.tar.xz

•  in the terminal run $ sudo pacman -U dwsim-6.2-2-x86_64.pkg.tar.xz. A lot of dependedencies are downloaded and installed.

•  pacman builds by default in the directory : /usr/lib/dwsim and makes a couple of launcher files in /usr/bin called dwsim and dwsim-classic

• open both files as root and check if the path is correct. In my case the path was wrong because was /usr/local/lib/dwsim so with /local added. I corrected manually all of them.

• at the end you can run dwsim just typing in a terminal, whitout root privilege: $dwsim or $ dwsim-classic

if problem persists,

After you have made sure,

1) Manjaro Setting manager

,2) Go to Hardware section and select Hardware configuration

3) Click on Autoinstall all opensource drivers(see image)

So you are set there's a chance that you may updates have unlinked old symlinks so type paste this in terminal

Okay you are set !

I confirm, thanks for the guide and for the necessary dependencies to install DWSIM on my ArchLinux.
Although this may be helpful, I followed the instructions and in the final section I don't know why it asked me for extra dependencies such as:
-qt5-serialport
-flitel
-apm_planner-bin
luckily I have an extra archlinux community repository called Arch4edu that provides some educational packages. I would also like to comment that if you are going to use it other than tiling window manager as in my case, I use Qtile since it could cause problems with the windows and it would be uncomfortable to work, so I recommend using another such as Plasma, Gnome, Budgie, etc.

I would also like to ask what would be a guide to install the thermoC plugin, because when I tried to install it I got "it already exists in the file system (it's part of dwsim)"