For the definition of the density, you don't need the mass per meter sq. but also, you can find the mass from the density and the volume (surface area by the depth used in 3-d)

Thanks but the volume of 2D simulation (the average density of a liquid and solid PCM *frontal area of 2D* width(1) while in 3D experimental work volume of PCM (Density of liquid pm * frontal area * width (0.32)). In Fluent width is equal to 1m for 2D case. Therefore both condition volumes will be different.

I haven't used Fluent to see how you are supposed to enter material parameters, but it is important to remember the main difference between the 2D and 3D images you drew. the 320mm dimension in your 3D drawing no longer exists in 2d. that dimension both into and out of the paper extend infinitely, both the blue and red region have exactly the same depth. of course the 'total mass' will be different if you extrapolated it to 320 mm to compare with the 3D, because it is an entirely different shape. the cross sections at the front and back of the 3D figure that would be entirely blue simply do not exist in the 2D model. such is the inherent approximation involved in simplifying to 2D

it is sometimes best to think of the 2D model as the infinitely thin slice of the 3D model at the center of that 320mm dimension. you do not have mass, you have mass per unit depth. (that's why it's often expressed as "1 meter", or "1 unit length" in depth, because it gives the same number for kg and kg/m). In the 2D simulation tools I've used, usually material parameters are entered, such as density, thermal properties, etc., and the tool determines the local 2D equivalent volumetric properties from the dimensions given.

Thanks Nicholas but how can I apply equivalent volumetric properties from the dimension given and could you explain more in details by any example?