Project ForgeThermodynamics
First Law of Thermodynamics
GATE 2014
Medium
1.5 kg of water is in saturated liquid state at 2 bar (vf=0.001061 m³/kg, uf=504.0 kJ/kg, hf=505 kJ/kg). Heat is added in a constant pressure process till the temperature of water reaches 400°C (v=1.5493 m³/kg, u=2967.0 kJ/kg, h=3277.0 kJ/kg). The heat added (in kJ) in the process is __________.
4158 kJ(± 3 accepted)
Explanation
For a closed system undergoing a constant-pressure process, Q=ΔH (since Q=ΔU+W and W=pΔV=Δ(pv) at constant p, so Q=Δu+Δ(pv)=Δh). Δh=h2−h1=3277−505=2772 kJ/kg. Q=m·Δh=1.5×2772=4158 kJ.
Source: GATE ME 2014 (Session 1 / Set-1) (2014)
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