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