Operation with gas flow rates below the critical minimum results in system instability indicated by {HEAD ~ temperature excursions} in the fluid and at the tube wall, by {TAIL ~ a rapid increase} and then decrease in overall pressure drop with decreasing gas flow rate, and by increased temperature differences between the temperature of the bulk fluid and the tube wall 
Operation with gas flow rates below the critical minimum results in system instability indicated by { HEAD ~ temperature excursions } in the fluid and at the tube wall , by { TAIL ~ a rapid increase } and then decrease in overall pressure drop with decreasing gas flow rate , and by increased temperature differences between the temperature of the bulk fluid and the tube wall
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 OTH OTH