Cryosurgical instrument with enhanced heat transfer
Cryosurgical instruments and methods utilizing improved heat transfer characteristics. A cryosurgical device includes: a tubular housing; a cryogen supply passage; a heat exchange enhancing member in the housing, disposed along a longitudinal axis of the housing; an annular cooling passage between the heat exchange enhancing member and the tubular housing; a tip cooling and cryogen flow directing section that transmits a temperature of a cryogen flow to the tip, and an insulation element in the tubular housing.
1. A cryosurgical instrument comprising:
a tubular housing having a longitudinal axis, a proximal end, and a tip at a distal end;
a cryogen supply passage extending from the proximal end to the distal end along the longitudinal axis, the supply passage having an upstream portion proximate to the proximal end and a downstream portion proximate to the distal end;
a heat exchange enhancing member in the housing, disposed along the longitudinal axis, and surrounding at least some of the downstream portion of the supply passage, the enhancing member having a plurality of return channels circumferentially disposed about the longitudinal axis and extending longitudinally through the enhancing member; and
a flow deflector between the tip and the supply passage, the flow director adapted and configured to deflect a cryogen flow exiting from the supply passage to the return channels and to absorb heat, thereby cooling the tip, the flow director fixedly and spacedly disposed from the supply passage,
wherein a flow of cryogen in the cryogen supply passage urges cryogen that has exited the cryogen supply passage to flow into the return channels, and
wherein a sum of cross-sectional areas of the plurality of return channels is about equal to a cross-sectional area of the supply passage.
2. The cryosurgical instrument of claim 1 , wherein the return channels are straight.
3. The cryosurgical instrument of claim 1 , wherein the cryogen absorbs heat in the return channels and exhibits two-phase flow in the supply channel and the return channels.
4. The cryosurgical instrument of claim 1 , wherein the plurality of return channels are disposed at a circumferential periphery of the heat exchange enhancing member and sealingly capped by an inner surface of the tubular housing.
5. The cryosurgical instrument of claim 1 wherein the plurality of return channels are disposed in the heat exchange enhancing member.
6. The cryosurgical instrument of claim 1 , wherein the return channels are adjacent to a circumferential periphery of the cryogen supply passage.