Calculation sequence
Step-by-step method
- Calculate hot- and cold-side heat-transfer rates.
- Average the two measured rates and calculate their balance mismatch.
- Check physical effectiveness and compare mismatch with the user-entered maximum.
MechanicalAdvancedEquipment
Heat-Exchanger Effectiveness Calculator
Calculate heat-exchanger effectiveness from hot- and cold-side inlet/outlet temperatures and capacity rates.
Why it matters: Effectiveness compares actual heat transfer with the thermodynamic maximum for the entered streams.
Calculated result
Engineering evaluation
Heat-exchanger effectiveness (ε)47.5 %
- Average measured heat transfer (Qavg)
- 380,000 Btu/h
- Hot/cold energy-balance mismatch (Bal)
- 10.53 %
- Entered maximum balance mismatch (Balmax)
- 10 %
- Minimum stream capacity rate (Cmin)
- 8,000 Btu/(h·°F)
- Maximum possible heat transfer (Qmax)
- 800,000 Btu/h
Engineering interpretation
The entered condition gives 47.5% effectiveness with 10.53% hot/cold energy-balance mismatch versus the entered 10% maximum. The entered energy-balance criterion is not met.
Important limitations
- A large energy-balance mismatch indicates inconsistent flow, properties, temperatures, boundaries, heat loss, transient operation, or measurement uncertainty.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Qh = Ch(Thi−Tho)
Qc = Cc(Tco−Tci)
Qavg = (Qh+Qc)/2
Cmin = min(Ch,Cc)
Qmax = Cmin(Thi−Tci)
ε = Qavg/Qmax×100
Bal = |Qh−Qc|/Qavg×100
require 0%≤ε≤100% and Bal≤Balmax
Current substitution
Qh = 400000; Qc = 360000; Qavg = 380000; Qmax = 800000; ε = 47.5%; Bal = 10.53%; Balmax = 10%.
Equation legend
Inputs and calculated quantities
- Ch
- Hot-stream capacity rate — Btu/(h·°F) or kW/K
- Cc
- Cold-stream capacity rate — Btu/(h·°F) or kW/K
- Thi
- Hot-stream inlet temperature — °F or °C
- Tho
- Hot-stream outlet temperature — °F or °C
- Tci
- Cold-stream inlet temperature — °F or °C
- Tco
- Cold-stream outlet temperature — °F or °C
- Balmax
- Entered maximum energy-balance mismatch — %
- ε
- Heat-exchanger effectiveness — %
- Qavg
- Average measured heat transfer — Btu/h
- Bal
- Hot/cold energy-balance mismatch — %
- Balmax
- Entered maximum balance mismatch — %
- Cmin
- Minimum stream capacity rate — Btu/(h·°F)
- Qmax
- Maximum possible heat transfer — Btu/h
Applications
How this calculation is used
Building design
Screen heat-exchanger performance at an operating point.
Construction
Check sensor locations, flow direction, and capacity-rate basis.
Commissioning
Calculate effectiveness and hot/cold energy-balance mismatch from simultaneous readings.
Quality controls
Assumptions and limitations
Assumptions
- Entered values represent one stable operating condition and use consistent measurement boundaries.
- Fluid and air properties are representative of the evaluated condition.
Limitations
- This is a preliminary evaluation and field-verification tool, not a final sizing or code-compliance determination.
- Manufacturer data, adopted codes, project criteria, and professional engineering review remain controlling.
Field use
Verification procedure
- Confirm measurement boundaries, operating mode, and instrument calibration.
- Stabilize the system and record simultaneous readings.
- Compare the calculation with project requirements and manufacturer data before disposition.
Common engineering mistakes
- Mixing values from different operating conditions.
- Using nominal rather than measured flow, temperature, power, or fluid properties.
Technical basis
References and source standards
- ASHRAE Handbook—FundamentalsPsychrometrics, heat transfer, load relationships, and HVAC calculation context; verify the licensed current edition during professional review.
- U.S. Department of Energy—Better Buildings Solution CenterFederal energy-performance and HVAC equipment guidance; project and manufacturer data remain controlling.
- NIST Guide for the Use of the International System of UnitsFederal unit-system and conversion reference used for SI/I-P presentation.
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