<li>Most ES programs assume the indoor air is completely mixed and with uniform properties. This may not be true for most buildings.</li>
<li>ES programs do not solve the air movement and contaminant transportation in the space.</li>
<li>detailed time-dependent and spatial distribution of many parameters</li>
<li>accurate indoor air velocity and temperature distributions</li>
<li>needs a lot of computation time</li>
- The indoor air temperature gradient and covective heat transfer from CFD can used in an ES model for more accurate energy calculation.
- CFD can accurately simulate natural ventilation driven by wind effect and stack effect, that can also be used in ES model.
- ES can provide more accurate flow and thermal boundary conditions for CFD simulation
CFD can also be exteneded to solve heat transfer in solid material, even with an appropriate radiation model, HVAC system model, and plant model, the extended CFD program can have the functions of both ES and CFD programs. But it is very eompztationally expensive.