The method 6 wherein the step of injecting a flow of cold cryogen vapor includes {HEAD ~ the steps} of injecting at least a first flow of cold cryogen vapor into the first conduit means, and injecting {TAIL ~ at least a second flow} of cold cryogen vapor into the second conduit means 
The method 6 wherein the step of injecting a flow of cold cryogen vapor includes { HEAD ~ the steps } of injecting at least a first flow of cold cryogen vapor into the first conduit means , and injecting { TAIL ~ at least a second flow } of cold cryogen vapor into the second conduit means
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH