The packed bed of fixed packing elements acts as {HEAD ~ a gas distributor}, as well as causing good gas/liquid contact, to provide an even flow of {TAIL ~ gas} across essentially the entire cross sectional area of the packed bed of mobile packing elements 
The packed bed of fixed packing elements acts as { HEAD ~ a gas distributor } , as well as causing good gas / liquid contact , to provide an even flow of { TAIL ~ gas } across essentially the entire cross sectional area of the packed bed of mobile packing elements
OTH OTH OTH OTH 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 OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH