Then the refrigerant flows downwardly through header 54 and enters the two tubes forming the second tube circuit 32b arranged in {TAIL ~ series} with {HEAD ~ the upper tube circuit 32a} 
Then the refrigerant flows downwardly through header 54 and enters the two tubes forming the second tube circuit 32b arranged in { TAIL ~ series } with { HEAD ~ the upper tube circuit 32a }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD