GB831788A - Heat exchange equipment and method - Google Patents

Abstract

831,788. Heat exchangers. CHEMETRON CORPORATION, [formerly NATIONAL CYLINDER GAS CO.]. June 27, 1956 [July 20, 1955], No. 19876/56. Class 64(3) In a method of operating a heat exchanger in which a heat transfer medium flows along a helical path 12 formed within a rotary drum 4 over an external surface of which passes a flowable material such as starch slurries, confections syrups or viscose to be processed, the heat transfer medium is one which, under the operating conditions prevailing in the heat exchanger, is present in both liquid and vapour state, the hand of the helical path and direction of through put of the heat transfer medium, and the direction of rotation of the drum, being selected so as to minimize the absolute angular velocity of the heat transfer medium and thereby minimize the formation of a layer of liquid-phase heat transfer medium on theheat exchange surface of the drum. Heat transfer media mentioned are steam, brine, diphenyl or diphenyl oxide or a mixture thereof, ammonia and fluorine refrigerants. In the form shown, steam or other heat transfer medium passes up through tube 29 and then downwardly through the helical path 12 in rotary drum 4 from which condensate is discharged through ports 33, flowing thence through tube 36 leading to exit conduit 48. Tubes 29 and 36 rotate with the drum 4. The flowable material to be processed flows through pipe 25 to space 20, through annular passage 5 between drum 4 and a stationary outer shell 3 to a head space 21 and thence out through passages 21, 23. Helical baffle 28 in steam. passage 12 acts to impart angular velocity to steam, and the speed and direction of the drum 4 is so selected that the effect of centrifugal force tending to throw steam condensate on to the drum wall and thereby reduce the heating effect of the steam, is eliminated. The steam passage 12 may decrease in cross-sectional area from the inlet to the outlet to compensate for the decrease in volume of the steam as it condenses. This may be effected by progressively decreasing the pitch of helix 28. A helical rib 18 may be provided on the external surface of the rotary drum 4 to mix or pump through the passage 5 the flowable material to be processed. A jacket 14 through which a heat transfer medium passes surrounds the shell 3 and is itself surrounded by thermal insulation 16. Longitudinal thermal expansion and contraction of the jacket 14 is permitted by bellowslike member 17.