The method
Before using the result
- Constant supplied air density and specific heat. Sensible heat only: latent loads and equipment inefficiencies are excluded.
Worked examples
These original training examples illustrate the method for North American Technician Excellence Certification (NATE). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Translate measured duct airflow into dry sensible heating or cooling duty. Practise identifying which given air density and specific heat belong in an HVAC heat balance.
- Air volume flow
- 1,800 m³/h
- Air density
- 1.2 kg/m³
- Specific heat (J/kg·K)
- 1,006
- Temperature change (out − in)
- 10 K
- ṁ = 1.2 × 0.5 = 0.6 kg/s.
- Heat rate = 0.6 × 1006 × 10 = 6036 W.
- Mass flow: 0.6 kg/s
- Sensible heat rate: 6,036 W
Positive means sensible heat added to the air; negative means removed.
2. Comparison example
Compare a different supplied condition using the same method. For Technical Conquer, the important check is that the input meaning, units and method assumptions still match the problem.
- Air volume flow
- 1,800 m³/h
- Air density
- 1.2 kg/m³
- Specific heat (J/kg·K)
- 1,006
- Temperature change (out − in)
- -8 K
- ṁ = 1.2 × 0.5 = 0.6 kg/s.
- Heat rate = 0.6 × 1006 × -8 = -4828.8 W.
- Mass flow: 0.6 kg/s
- Sensible heat rate: -4,828.8 W
Positive means sensible heat added to the air; negative means removed.
Check your understanding
1. Which relationship is used?
Mass flow = density × volume flow; sensible power = mass flow × cp × ΔT.
2. Which assumption should you check first?
Constant supplied air density and specific heat. Sensible heat only: latent loads and equipment inefficiencies are excluded.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to North American Technician Excellence Certification (NATE) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.