Shelter consists of many components like AC, UPS, workstation unit, PDB unit, batteries etc. It is important that AC duct design should be such that, it can supply required flow rate through the various louvers. Also during normal operation when external power supply present, AC should maintain a temperature within various Units below critical limits. HVAC design becomes more complex with different heat loads on various Units. Hence performance of various Shelter units depend on efficient cooling and this can be achieved by CFD. Also in ‘No external power supply scenario’ CFD help in determining the time period for which temperature within various Shelter Units doesn’t exceed critical limits.