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