Estimate the theoretical downstream temperature, dilution, and thermal load after a heated discharge is completely mixed with a defined receiving-water flow.
Inputs
User assumption: fraction of the entered receiving flow that participates in complete mixing.
This is a complete-mixing heat balance. It does not predict near-field plume geometry, mixing-zone dimensions, stratification, currents, wind, or diffuser performance.
Results
Mixed temperature—
Temperature rise above ambient—
Effective participating receiving flow—
Modelled total mixed flow—
Ambient-to-discharge ratio—
Total dilution factor—
Thermal load relative to ambient—
Temperature-difference reduction—
Heated discharge5.00 m³/s at 35.00 °C
+
Participating receiving flow50.00 m³/s at 18.00 °C
Discharge represents 9.1% of the total mixed flow.
Tmix = (Q1T1 + Q2,effT2) / (Q1 + Q2,eff) Q2,eff = f · Q2 Pthermal = ρ · cp · Q1 · (T1 - T2)
Reverse-solve modes rearrange the same complete-mixing heat balance. The temperature equation assumes both streams have approximately the same density and specific heat; the entered properties are used to calculate discharge thermal load.
Discharge: 5 m³/s at 35 °C
Receiving flow: 50 m³/s at 18 °C
Complete-mixing temperature: 19.55 °C
Rise above ambient: 1.55 °C
Thermal load: ≈355.8 MWth
The result is a complete-mixing energy balance. It does not describe the temperature immediately beside an outfall.
Frequently Asked Questions
No. It calculates a complete-mixing heat balance only. It does not predict plume geometry, surface trapping, stratification, currents, tides, wind, or diffuser behavior.
For rivers, use the flow expected to participate in eventual cross-sectional mixing. For lakes, bays, estuaries, or coastal waters there may be no single defensible receiving-flow value; use a specialist mixing model for design or permitting.
It is a user-defined assumption describing what fraction of the entered receiving flow participates in the complete-mixing calculation.
The ambient-to-discharge ratio is Q₂,eff/Q₁. The total dilution factor is (Q₁+Q₂,eff)/Q₁.
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