Many beneficial human manufacturing and energy production activities involve the transport of a heated fluid in a fluid conduit situated in a cold environment. Where the fluid is susceptible to solidification or becoming unmanageably viscous because of heat loss to the cold environment, prudent engineering practices include insulating pipes against passive heat loss to the environment and/or actively heating the fluid conduit along its length.
Heat loss and its attendant consequences may become particularly severe where flow of the heated fluid through the conduit is interrupted. The conduit, containing the heated liquid gradually cools via heat loss to the environment and the fluid may solidify or become unmanageably viscous within the conduit. When flow is resumed, the thermally depleted matter within the fluid conduit may prevent or delay the resumption of fluid flow within the fluid conduit. Problems can be particularly severe when the heated fluid readily crystallizes on cooling, as is the case with relatively pure phenol (melting point 43° C., CAS No. 108-95-2) or otherwise forms solids on cooling. (See natural gas hydrates for example.)
Thus, heat retention within fluid conduits may be critical to the efficient operation of facilities in which a hot fluid susceptible to deleterious phase changes in response to heat loss to a cold environment is transported. There is at present a particular need for improved thermal control in subsea hydrocarbon production operations in which hot production fluids may undergo deleterious phase changes as a result of heat loss to the cold subsea environment. The present invention provides one or more embodiments enabling improved thermal control in such environments.