In ANSYS Fluent, when the energy equation is enabled and viscous heating is enabled, must pressure work also be turned on?
January 25, 2023 at 7:17 amFAQParticipant
Consider flow through a capillary ID 1 mm, Length 20 mm, adiabatic wall and inlet velocity 0.02 m/s, 300 K. The fluid has a viscosity = 0.8 Pa-s, density = 600 kg/m3, thermal conductivity = 0.1 W/m-K, and specific heat = 2600 J/kg-K. Therefore, the Ryenolds number is very low, Re = 0.015, and the Prandtl number if very high, Pr = 20800. In such a case, when you turn on viscous heating only, the outlet temperature will be LESS than the inlet temperature! This problem is rectified by turning on pressure work. The procedure will be explained and described further below. We know h = u + P/rho where h = specific enthalpy; u = specific internal energy; P = pressure; rho = density. Hence delta(h) = delta(u) + delta (p/rho) = delta (u) + P.delta(1/rho) + (1/rho).delta(P). For incompressible liquids with constant density, P.delta(1/rho) = 0; but, we need to account for (1/rho).delta(P). For gases, both incompressible and compressible, depending upon whether it is constant volume or constant pressure process, the appropriate pressure work remains. When viscous heating is turned on, the increase in enthalpy needs to be accounted for by the pressure work term. Otherwise, as in the sample problem case, you will see a fictitious drop in exit temperature to satisfy the enthalpy balance. How to turn on Pressure Work in ANSYS Fluent? In the text interface Define->Models->Energy; Fluent will prompt you for inclusion of viscous dissipation term, pressure work term, kinetic energy term.
Introducing Ansys Electronics Desktop on Ansys Cloud
The Watch & Learn video article provides an overview of cloud computing from Electronics Desktop and details the product licenses and subscriptions to ANSYS Cloud Service that are...
How to Create a Reflector for a Center High-Mounted Stop Lamp (CHMSL)
This video article demonstrates how to create a reflector for a center high-mounted stop lamp. Optical Part design in Ansys SPEOS enables the design and validation of multiple...
Introducing the GEKO Turbulence Model in Ansys Fluent
The GEKO (GEneralized K-Omega) turbulence model offers a flexible, robust, general-purpose approach to RANS turbulence modeling. Introducing 2 videos: Part 1 provides background information on the model and a...
Postprocessing on Ansys EnSight
This video demonstrates exporting data from Fluent in EnSight Case Gold format, and it reviews the basic postprocessing capabilities of EnSight.
- Simulating Battery Pack Cooling System Using Ansys Fluent
- Thermal Analysis of a Radiator Using Ansys Fluent
- Defining heat transfer coefficient (HTC)
- ANSYS Fluent Student: Conjugate Heat Transfer in a Heat Sink
- ANSYS Fluent: Overview of the Mapped Interface Technique for CHT Simulations (18.2)
- How to set up a heat source in CFX in a subdomain that results in a constant temperature
- Tips for resolving unphysical temperatures and poor convergence with CHT cases.
- Plate Heat Exchanger Solver Setup in ANSYS Student – Part 1
- How much number of faces per cluster value should be used for S2S radiation model in ANSYS Fluent?
- What are the TUI commands to enable / disable Shell Conduction?