{HEAD ~ at least one thermal exchange} means composed of {TAIL ~ parallel inner and outer plastic sheet means} separated by a plurality of parallel flat ribs oriented normal to said sheet means and fused to said sheet means to form a plurality of parallel channels 
{ HEAD ~ at least one thermal exchange } means composed of { TAIL ~ parallel inner and outer plastic sheet means } separated by a plurality of parallel flat ribs oriented normal to said sheet means and fused to said sheet means to form a plurality of parallel channels
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL 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 OTH OTH