Solution — Mass and heat imbalance

Run or resume the case and inspect the mass imbalance indicator.
With heat transfer enabled, inspect the heat indicator. Hover over it for rates in watts and the sample time.
Compare the balance with residuals and monitored quantities. If a steady thermal run reaches its iteration limit before converging, review the case and resume with a larger limit when appropriate.

Input or value	Meaning	Units
Mass imbalance	Difference between total incoming and outgoing mass flow, displayed as a relative imbalance.	%
Heat imbalance	100 × (heat input − heat output) / heat input. If input is zero, nonzero output is used for normalization.	%
Heat rates	Boundary conductive heat, including turbulent thermal diffusion, and thermal energy transported by flow relative to TRef. Values update at each solver step or steady iteration.	W in the indicator tooltip
Transient storage	Positive stored energy is included in output; released stored energy is included in input.	Included in the heat-rate accounting
Heat indicator colors	Absolute imbalance: green below 1%; orange from 1% to below 3%; red at 3% or above.	%

A small imbalance is one convergence check; it does not establish mesh independence or solution accuracy. Positive heat imbalance means more energy enters than leaves.
The heat monitor supports single-region buoyantBoussinesqSimpleFoam and buoyantBoussinesqPimpleFoam cases with constant material properties and without radiation or fvOptions source terms. Transient storage supports Euler and backward time schemes.
Other energy equations, CHT, radiation, source terms, missing data, and zero thermal throughput display N/A until complete accounting is available. N/A does not mean zero error.
A saved complete sample is restored when a project is reopened. Older results need to be resumed with the monitor enabled to obtain a sample.
For supported steady thermal cases, automatic stopping checks the final residuals: combined velocity ≤ 1e-4 and temperature ≤ 5e-4, unless residualControl targets are specified. Pressure and turbulence residuals are also checked. Absolute heat imbalance must remain below 1% for five consecutive complete iterations. If the solver stops or reaches its limit first, the log reports that thermal convergence was not reached.

Solution → Mass and heat imbalance