Question # 03: (15 points) Background: A spherical cryoprobe may be imbedded in diseased tissue for the purpose of freez

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Question 03 15 Points Background A Spherical Cryoprobe May Be Imbedded In Diseased Tissue For The Purpose Of Freez 1 (75.05 KiB) Viewed 46 times

Question # 03: (15 points) Background: A spherical cryoprobe may be imbedded in diseased tissue for the purpose of freezing and thereby destroying, the tissue. Consider a probe of 3-mm diameter whose surface is maintained at -30°C when embedded in tissue that is at 37°C. A spherical layer of frozen tissue forms around the probe, with a temperature of 0°C existing at the phase front (interface) between the frozen and normal tissue. If the thermal conductivity of the frozen tissue is approximately 1.5 W/m K, and heat transfer at the phase front may be characterized by an effective convection heat transfer coefficient of 50 W/m²K. KNOWN: Diameter and surface temperature of a spherical cryoprobe. Temperature of surrounding tissue and effective convection coefficient at interface between frozen and normal tissue. FIND: Thickness of frozen tissue layer. SCHEMATIC: 1 = 0.0015 m 2 Normal tissue Too 37 °C h=50 W/m² K cond Probe Ts,1 = -30 °C Ts,2 = 0 °C Frozen tissue, k = 1.5 W/m-K aconv ASSUMPTIONS: (1) One-dimensional, steady-state conditions, (2) Negligible contact resistance between probe and frozen tissue. (3) Constant properties, (4) Negligible perfusion effects.