Mixing Temperature Calculator
Find the final temperature when two streams or batches of liquid mix, without phase change or heat loss, and the flow of one stream needed to hit a target temperature.
- Tmix = (m₁c₁T₁ + m₂c₂T₂) ÷ (m₁c₁ + m₂c₂) = 44.03 °C
- For a target: m₁ = m₂c₂(Tt − T₂) ÷ [c₁(T₁ − Tt)]
Mixing Energy Balance
m₁ for target = m₂c₂(Tt − T₂) ÷ [c₁(T₁ − Tt)]
m is the mass flow or mass of each stream, c the specific heat and T the temperature. Assumes no heat loss, no phase change and no heat of mixing. Water is about 4.18 kJ/kg·K; light oils about 1.9 to 2.1.
Worked example
10 kg/s of water at 80 °C mixed with 15 kg/s at 20 °C gives about 44.0 °C. To reach exactly 40 °C you need about 7.5 kg/s of the hot stream.
Frequently Asked Questions
Does it work for different liquids?
Yes, as long as they do not react or change phase. Use each liquid’s own specific heat.
Can I use volume flows?
Only if densities are similar. Otherwise convert to mass flow first.
What about steam injection?
Steam condensing releases latent heat, so this simple balance does not apply. Use steam enthalpy instead.
Learn more on the blog
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