AFT Application Topics
Pipe Flow with Heat Transfer
Piping networks often have heat transfer present that must be modeled and quantified. AFT Fathom and AFT Arrow allow users to model heat transferred from pipes, heat exchangers and rotating or reciprocating equipment (pumps and compressors). An overall system energy balance is performed during the simulation to characterize any heat transfer.
Heat lost or gained in pipes can be modeled with several heat transfer models including convection heat loss/gain to ambient conditions. Piping insulation can be included in the heat transfer calculations. An important output from the AFT software simulation is the surface temperature of the bare pipe or insulation. Understanding the surface temperature can help ensure compliance with safety regulations such as those from OSHA. See Resources below for more information on safety regulations.
AFT software not only models pressure drop but also heat transfer from heat exchangers. Numerous heat exchanger thermal models are available using NTU-based methods as well as various user specified heat rate models.
Temperature rise from heat of compression from compressors is handled within AFT Arrow. While typically less important in liquid flow, temperature rise from pumps can be modeled.
When heat transfer is modeled in AFT Fathom, all fluid physical properties such as fluid density and viscosity are dynamically updated during the simulation as the temperature is iterated for each pipe. AFT Arrow always models heat transfer, and gas physical properties are thus always dynamically updated for each pipe. Further, physical properties vary along each pipe as AFT Arrow breaks each pipe into sections for calculation.
Resources
Standard – OSHA Surface Temperature Standards Interpretation Including 1910.261(k)(11)