Conditional Thermomechanical Feasibility of a Bimetal Actuated Thermal Capsule

A miniature thermal capsule must cool rapidly into a narrow temperature band while suppressing heat loss after contact release. This study couples geometry-dependent actuator stiffness, unilateral contact and pressure-dependent gap transfer to a two-node enthalpy model. A massless intermediate node enforces heat-flux continuity between the joint and its downstream resistance. A grid of 10,800 configurations tests entry into −21 to −19 °C within 3 s and uninterrupted residence for at least 30 s, together with provisional displacement and force requirements. At 1, 10 and 100 Pa, respectively, 148, 68 and 0 of 3600 configurations pass at nominal inputs. No nominally feasible candidate passed all 16 tested tolerance corners. Nominal residence at 1 and 10 Pa is right-censored, with lower bounds of 30.253 and 30.254 s, respectively; at 100 Pa the observed residence is 7.333 s. These results assume an external resistance of 22.80 K W⁻¹ and a gap regularization length of 1 μm. Illustrative metal sections explain only 1.03% of that resistance, making the counts conditional on an unidentified assembly and boundary network. Removing phase excess leaves the nominal zero-gas response unchanged, indicating isolation-dominated residence in that scenario. The contribution is a quantified loss of feasibility at tested tolerance corners, not experimental performance or an exclusion of all continuous designs.