Project ForgeHeat Transfer
Heat Exchangers
GATE 2018
Hard
An insulated tank has 1000kg liquid (Cp=10 kJ/kg·K), heated by steam condensing at 180°C in a coil (area 0.1m², U=1000 W/m²·K). The time (hours) to raise the liquid from 20°C to 80°C is (rounded off to second decimal place)
13.06 hours(± 0.3 accepted)
Explanation
τ=mCp/(UA)=10,000,000/100=100,000s. T(t)=180−160e^(−t/τ). At T=80: 100=160e^(−t/τ) ⟹ t=τ·ln(1.6)=100,000×0.47=47,000s=13.06h.
Source: GATE CH 2018 (2018)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.