{HEAD ~ Contact surfaces} are arranged inside {TAIL ~ the fluid bed} whose total area is the same as up to 500 times the area of the approach flow bottom of the fluid bed 
are arranged inside
{ HEAD ~ Contact surfaces } are arranged inside { TAIL ~ the fluid bed } whose total area is the same as up to 500 times the area of the approach flow bottom of the fluid bed
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH