Hot liquid is flowing in a steel pipe with a 22-mm inner diameter and a 27-mm outer diameter. The pipe outer surface is subjected to a uniform flux of 1200 W/m2 for a length of 1 m. The pipe inner surface is coated with a thin polyvinylidene fluoride (PVDF) lining. The hot liquid flowing inside the pipe has a mean temperature of 120°C and a convection heat transfer coefficient of 50 W/m2•K. The ASME Code for Process Piping (ASME B31.3-2014, A323) recommends a maximum temperature for PVDF lining to be 135°C. Does the surface temperature of the PVDF lining comply with the recommendation of the code?
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Hot liquid flows in a pipe with PVDF lining on the inner surface. The pipe outer surface is subjected to uniform heat flux. The liquid mean temperature and convection heat transfer coefficient are given. Determine whether the surface temperature of the lining complies with the ASME Code for Process Piping.
Assumptions1 Steady operating conditions. 2 Heat transfer is one-dimensional through the pipe wall. 3 Surface temperature is uniform. 4 Thermal properties are constant.
AnalysisThe surface energy balance on the PVDF lining is
The outer and inner surface areas of the pipe are
Solving for the lining surface temperature Ts,
DiscussionThe surface temperature of the lining exceeds the maximum temperature recommended by the ASME Process Piping code for PVDF lining. A different thermoplastic lining should be used. Polytetrafluoroethylene (PTFE) lining has a recommended maximum temperature of 260°C by the ASME Code for Process Piping (ASME B31.3-2014, A323), which would meet these conditions.
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