How to calculate the volume of a clipped iso surface
 

Hello everyone.

I am simulating the the flow of hot sir through a rock bed for thermal energy storage. I have completed the simulation and would like to calculate the volumetric efficiency of the rock bed. The volumetric efficiency is the volume of rocks heated above 600K divided by the total volume of the rock bed. I am struggling to calculate the volume of rocks above 600K in fluent. I have created a clipped iso surface, which displays the portion of the rock bed above 600K but I can’t calculate the volume of this clipped iso surface. Any help will be much appreciated. Thanks!