Subtopic: Steady state heat transfer in conduction, convection and radiation
Question Statement:
Convective film heat transfer coefficient (h) of air (thermal conductivity = 0.025 W m⁻¹ K⁻¹) in W m⁻² K⁻¹, trapped between two parallel glass panes in a window 1.5 mm apart, is
Options:
(A) 3.75
(B) 16.67
(C) 37.52
(D) 60.21
Official Answer Key:
B
Step-by-Step Solution & Explanation
Air trapped in a 1.5 mm gap cannot circulate; heat transfer is by pure conduction across the film.
Equating conduction and convection resistances: h = k/L.
h = 0.025/0.0015 = 16.67 W m⁻² K⁻¹.
Distractor (A) 3.75 = k × L × 10⁵-type manipulation, i.e. multiplying instead of dividing by the gap.
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.