Apparatuses and methods for heating and cooling glass tubing

A system for producing glass tubing, the system comprising:

• a bowl comprising:
• at least one cylindrical container having an orifice ring extending from a bottom of the cylindrical container, the orifice ring defining an orifice in the bottom of the cylindrical container;
• and
• a blow tube disposed within the cylindrical container and extending through the orifice, the blow tube operable to deliver a gas flow proximate the orifice ring;
• and
• a muffle comprising:
• an inlet end coupled to the bowl;
• an outlet end having an inner dimension larger than an inner dimension of the inlet end;
• a sidewall extending from the inlet end to the outlet end, wherein a radial distance from a center axis of the muffle to an inner surface of the sidewall increases from the inlet end to the outlet end and the inner surface of the sidewall is substantially free of abrupt changes in the radial distance from the center axis to the inner surface;
• and
• a channel positioned between an outer surface of the sidewall and an insulating layer disposed about the sidewall, the channel operable to pass a heat transfer fluid into thermal communication with the sidewall to provide cooling to the sidewall;
• wherein the muffle is operable to control a temperature of the glass tubing drawn from the bowl.