Thermal Analysis of Vent Pipes and Clamped Saddles Interacting with Pipe Racks

Abstract

Vent pipes of natural gas compression stations can achieve very low temperatures during depressurization operations, and for such a reason their construction material is often specified to have a very low minimum design temperature. However, the pipe supporting structure can have higher design temperature specifications. During the depressurization operation, the vent pipe saddles are subject to a transient thermal evolution reflecting the vent pipe material cooling, governed by combined transient conduction and convection; however, the cooling of the supporting structure is less severe than that of the vent pipe, because of thermal inertia and ambient air mitigation. A transient heat transfer simulation scheme of typical saddle base supports, assimilated to rectangular fins, has been developed by modifying reference models and adopting a finite difference calculation approach. The new model has been validated in reference simulation scenarios, and it has been applied to typical pipe vent and associated supports configurations. The model allows one to determine the thermal interaction between pipes and supports and to assist in decision-making procedures for the engineering of the overall structure, as for instance the possible installation of thermal insulation if the cooling transmitted to pipe racks is excessive.