Heat transfer tubes and methods of fabrication thereof

A method of fabricating a metallic tube for boiling, the metallic tube being of a type having an outer surface for submersion in a refrigerant and an inner surface for contacting a liquid heat transfer medium to be chilled, the method comprising:

• (1) forming a plurality of helical ridges on the inner surface of the tube;
• (2) providing a plurality of radially outwardly extending helical fins on the outer surface of the tube with channels extending between adjacent fins;
• (3) grooving the fins to provide notches and a nucleate boiling pore at a bottom of each intersection of a notch and a channel;
• (4) flattening the fins whereby flattened adjacent fins form an enclosed channel segment extending between neighboring pores so that vaporized refrigerant in the enclosed channel leaves the channel only by the pores, adjacent notches being non-contiguously spaced apart whereby a flattened fin is intermediate neighboring pores:
• the fins and notches being spaced whereby the pores have an average area less than 0.00009 square inches.

A method of fabricating a metallic tube for boiling, the metallic tube being of a type having an outer surface for contacting a refrigerant and an inner surface for contacting a liquid heat transfer medium to be chilled, the method comprising:

• (1) forming a plurality of helical ridges on the inner surface of the tube:
• (2) providing a plurality of radially outwardly extending helical fins on the outer surface of the tube;
• (3) notching the fins to provide nucleate boiling pores by forming a plurality of first notches in a first direction and forming a plurality of second notches in a second direction;
• the fins and notches being spaced whereby the pores have an average area of less than 0.00009 square inches:
• and
• wherein the notching of the plurality of second notches in the second direction occurs at a cross notch pitch which differs from a pitch of the first set of notches.

A method of fabricating a metallic tube for boiling, the metallic tube being of a type having an outer surface for contacting a refrigerant and an inner surface for contacting a liquid heat transfer medium to be chilled, the method comprising:

• (1) forming a plurality of helical ridges on the inner surface of the tube;
• (2) providing a plurality of radially outwardly extending helical fins on the outer surface of the tube;
• (3) notching the fins forming a plurality of first notches in a first direction;
• (4) notching the fins forming a plurality of second notches in a second direction;
• wherein the notching of the plurality of second notches in the second direction occurs at a pitch to vary the average pore size.