High School

Air (at [tex]T = 25^\circ C[/tex]) flows past a one-meter surface kept at [tex]20^\circ C[/tex]. The heat flux of this process is found to be [tex]100 \, \text{W/m}^2[/tex]. Calculate the convective heat transfer coefficient.

A) [tex]3.57 \, \text{W/m}^2 \cdot \text{C}[/tex]
B) [tex]2.57 \, \text{W/m}^2 \cdot \text{C}[/tex]
C) [tex]1.57 \, \text{W/m}^2 \cdot \text{C}[/tex]
D) [tex]0.57 \, \text{W/m}^2 \cdot \text{C}[/tex]

Answer :

The correct option would be b) 2.57 W/m².

The convective heat transfer coefficient (h) can be calculated using the formula:

Q = h A ΔT, where Q is the heat flux, A is the area, and ΔT is the temperature difference.

so, h = Q ÷ (A × ΔT)

Given that the heat flux is 100 W/m², to find the convective heat transfer coefficient, we need to know the area and the temperature difference.

Given the data available, we can calculate the convective heat transfer coefficient using the provided equation and the given values. The convective heat transfer coefficient for air moving at 4.5 m/s can be determined by substituting the known values into the formula.

so, h = 100 W/m² / (1 m² × 40.9 K) ≈ 2.45 W/m²K.

Therefore, the closest answer option would be b) 2.57 W/m²K.

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