Ixnay on blabbing about your design until you are ready to have people sign Non-Disclosure Agreements.
To solicit the best response, you could define the design requirement, and your hardware platform.
Design and modelling software could be grouped into box modelers, NURBs modelers, CAD software, automatic mesh capture software, and others.
The workflow includes modelling, texture mapping, rigging animating and rendering. Before you get into simulating gas flows, and etc.
The workflow within any one program can be intimidating; believe, me I know. The result you require may require passing files from one program to the next; for instance you may need to prepare templates in Photoshop to import into your modeller.
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Of course all that is non-responsive. What you need is a free cross-platform program that will do it all, with light-weight system requirements.
May I suggest Wings 3D. I finally settled on it because I can understand the operation. It is a simple box modeler, but it will do texture mapping and rendering. There is a very clear control to tell you whether you are working with the whole object, faces, edges or vertexes. And operations have you select something, then right-click to get a context sensitive menu, fiddle with the middle button or Tab for numeric input or whatever, then left click to accept. That is simplistic, there are modifier keys and additional tools under the menus, but it made things accessible to me. There are tutorials on YouTube.
There certainly are other options.