In {HEAD ~ one embodiment}, {TAIL ~ the pipe} itself forms a part of the heat exchanger while in another embodiment, the heat exchanger is closed so as to form a heating chamber 
In { HEAD ~ one embodiment } , { TAIL ~ the pipe } itself forms a part of the heat exchanger while in another embodiment , the heat exchanger is closed so as to form a heating chamber
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH 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 OTH OTH OTH OTH OTH OTH