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Heat exchanger effectiveness and sizing depend on flow rates, temperatures, and heat transfer area. Design ensures adequate thermal transfer.
Formel
Calculate: Q = U×A×ΔT_lm (log mean temperature difference)
- Q
- U×A×ΔT_lm (log mean temperature difference) — U×A×ΔT_lm (log mean temperature difference)
- U
- U value — Variable used in the calculation
- A
- A value — Variable used in the calculation
Trin-for-trin guide
- 1Calculate: Q = U×A×ΔT_lm (log mean temperature difference)
- 2Account for flow arrangement (counterflow, cross-flow, parallel)
- 3Size area for required heat transfer
Løste eksempler
Input
Q = 50 kW, U = 2000 W/m²·K, ΔT_lm = 10 K
Resultat
A ≈ 2.5 m² required
Determines exchanger size
Almindelige fejl at undgå
- ✕Using arithmetic mean instead of log mean temperature difference
- ✕Neglecting fouling resistance
Ofte stillede spørgsmål
Why is counterflow more efficient?
Counterflow maximizes temperature driving force throughout; parallel-flow has smaller LMTD.
What determines overall U coefficient?
U depends on fouling, scale, fluid properties. Typical 500-5000 W/m²·K depending on fluids.
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