CORE PRINCIPLES
What to establish first
- Conduction depends on conductivity, area and distance.
- Convection is represented by a heat-transfer coefficient that depends on flow and geometry.
- Overall coefficients combine thermal resistances in series.
Heat Transfer
Conduction, convection, radiation and heat-exchanger calculations.
MODULE OVERVIEW
Heat Transfer in practical engineering work.
Heat transfer is driven by temperature difference through conduction, convection and radiation. Good thermal design identifies the dominant resistance and the temperature conditions that create it.
DESIGN CONCEPTS
Terms worth checking
- Thermal resistance
- Overall U-value
- Temperature difference
Common applications: Heat exchangers · Insulated equipment · Electronics and process cooling
KEY RELATIONSHIP
Overall heat-transfer rate
Q = UAΔT
- U — overall coefficient, W/m²·K
- A — transfer area, m²
- ΔT — applicable temperature difference, K
For an exchanger, the required mean temperature difference and correction factor must be selected separately.
WORKED EXAMPLE
Known values → substitution → interpretation
- Known values
- U = 250 W/m²·K; A = 4 m²; ΔT = 30 K
- Method
- Q = 250 × 4 × 30
- Interpretation
- The preliminary heat-transfer rate is 30 kW.
KEY DESIGN CHECKS
Confirm the conditions behind the number
- Define the governing load case, duty cycle and required design life before using a simplified relation.
- Use compatible units and material data for the actual condition, temperature and manufacturing state.
- Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
- Applying overall heat-transfer rate outside the assumptions shown on this page.
- Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
- Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
RELATED RESOURCE
Open Heat Transfer Rate Calculator
Calculate a transparent U-A-temperature-difference estimate.
Open related resource →REFERENCES & LIMITATIONS
Use this content as a transparent starting point
ReferenceF. P. Incropera et al., Fundamentals of Heat and Mass Transfer.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
RELATED ENGINEERING