i am not a cpu expert. For eleminating heat ,[cpu heating ] if possible try
1.use a set of heat sinks which can evaporate heat into atmosphere.For that ,
A)calculate heat evaporation from specified heat sink .Calculate multiples if needed.
2.Thermally connect heat sinks. i.e. heat sink set must be in one tempereture.
3. set heat sink firmally to plastic case.
4.use nets for ventillation in plastic case to atmospere [avoiding small creatures and rats etc.
if this is possible with plastic case dimensions ,fans may [far possibility ...]avoided.
# used to denote directly proportional to [in physics]
temperature outside [atmospheric] # tempereture inside plastic case. # tempereture at heatsink set .[or one heat sink as u use...]
1.temperture inside plastic case willbe slightly more than outside temperture.
2.temperture of heat sink will be more than temperture inside plastic case .
use NEWTON'S LAW OF COOLING for heat transfer to temperature determination inside plastic case..
use LAW OF HEAT TRANSFER IN ATMOSPHERE FROM ONE POINT TO ANOTHER [IN ATMOSPHERE.],FOR TEMPERATURE DETERMINATION BETWEEN ATMOSPHERE.[OUTSIDE & PLASTIC CASE INSIDE.]
@ means - almost directly proportional [strong relation ]
HEAT IN HEATSINK willbe # current inside CPU. # temperature at heatsink. @ wattage of processor.