Rubber O-rings are widely applied in the static and dynamic seals of machinery, energy, chemical, aviation, and other fields. Mechanical behavior and sealing performance of the O-ring were investigated in this paper. Effects of precompression amount, fluid pressure, friction coefficient on the static and dynamic sealing performances of the O-ring were studied. The results show that the maximum stress appears on the inside but not surface of the O-ring. The static sealing performance increases with the increasing of fluid pressure and compression amount. Reciprocating dynamic sealing performance of the rubber O-ring is different with its static sealing performance; the stress distribution and deformation are changing in reciprocating motion. Sealing performance in outward stroke is better than it in the inward stroke. Overturn of the O-ring occurs when the friction torque is greater than the torque that caused by fluid pressure in the inward stroke. Distortion, bitten, and fatigue failure are the main failure modes of the O-ring in the dynamic seal. Those results can be used in design, installation, and operation of rubber O-rings in static and dynamic seals.

In this paper, the numerical simulation model of an ellipsoidal protruded tube has been established considering thermal hydraulic performance. The flow field characteristics and heat transfer characteristics of an ellipsoidal protruded tube were investigated. Effects of protrusion configuration, depth, pitch, number, axis ratio, and angle on thermal hydraulic performance were discussed using the realizable k–ε model under the steady-state condition. These results show that protrusion volume has a major impact on thermal hydraulic performance. The protrusions make the zone of flows narrow down at the protrusion leading edge side and expand at the trailing edge side, which resulted in protrusions increased turbulence, flow mixing, flow separation, and boundary layer distribution, thus enhancing the heat transfer performance. The maximum of local Nusselt number is located at the protrusions leading edge, and the minimum of local pressure is located at central of the protrusion surface. The configuration has no significant effect on the thermal hydraulic performance. Furthermore, the optimal selection of parameters boosts the heat transfer by up to 130.9% and amplifies the pressure loss up to 103.2%.