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Water-Side Heat Transfer Calculator

Estimate hydronic heat transfer from fluid flow, temperature difference, and a user-entered fluid factor.

Why it matters: Water-side capacity is a core commissioning check for coils, chillers, boilers, and heat exchangers.

User inputs

Enter field measurements

4 inputs
Select the unit convention used for all values in this calculation.
gpm or L/sRepresentative measured or scheduled fluid flow.
°F or KLeaving minus entering temperature; magnitude is used for capacity.
Btu/(h·gpm·°F) or kJ/(L·K)For I-P water calculations, 500 is a rounded screening value. For SI with L/s, water is approximately 4.186 kJ/(L·K).

Calculated result

Engineering evaluation

No low-ΔT warning
Water-side heat transfer (Q̇)1,440,000 Btu/h
Fluid factor (F)
500 Btu/(h·gpm·°F)
Temperature difference (ΔT)
12 °F
Equivalent refrigeration (TR)
120 tons

Engineering interpretation

Estimated water-side capacity is 1440000 Btu/h. For water near typical HVAC temperatures, 500 is a common rounded I-P factor; glycol and temperature can materially change it.

Engineering knowledge center

Understand the calculation—not just the answer

2026-08-07 · Free Library
Governing relationships
Q̇ = F × V̇ × ΔT
TR = Q̇/12,000
Current substitution

Q̇ = F × V̇ × ΔT = 500 × 240 × 12 = 1440000 Btu/h.

Calculation sequence

Step-by-step method

  1. Obtain representative entering and leaving fluid temperatures.
  2. Use a fluid factor consistent with density and specific heat at the operating concentration and temperature.
  3. Multiply fluid factor, flow, and absolute temperature difference.

Equation legend

Inputs and calculated quantities

V̇
Fluid flow — gpm or L/s
ΔT
Fluid temperature difference — °F or K
F
Fluid heat-transfer factor — Btu/(h·gpm·°F) or kJ/(L·K)
Q̇
Water-side heat transfer — Btu/h
F
Fluid factor — Btu/(h·gpm·°F)
ΔT
Temperature difference — °F
TR
Equivalent refrigeration — tons

Continue the evaluation

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Engineering calculation disclaimer

These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.

Read the full use and limitation statement