{HEAD ~ The coolant} is introduced into {TAIL ~ the channels} co currently with the direction of flow of the reactants 
{ HEAD ~ The coolant } is introduced into { TAIL ~ the channels } co currently with the direction of flow of the reactants
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH