This permits {HEAD ~ the tubing} 18 to be of {TAIL ~ minimum area} since heat exchange from the collector to the second fluid will be conducted over a longer period of time 
to be of
This permits { HEAD ~ the tubing } 18 to be of { TAIL ~ minimum area } since heat exchange from the collector to the second fluid will be conducted over a longer period of time
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH