The tube bundle is sealed within a shell, which is {TAIL ~ a sealed chamber} through which {HEAD ~ a working liquid}, such as water, is circulated and is heated by the hot tubes 
through is circulated
The tube bundle is sealed within a shell , which is { TAIL ~ a sealed chamber } through which { HEAD ~ a working liquid } , such as water , is circulated and is heated by the hot tubes
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL REL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL OTH OTH OTH OTH OTH OTH OTH