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What amount of heat would be required to produce 4.4 kg of steam at a pressure of 6 bar and temperature of 250°C from water at 30°C ? Take specific heat for superheated steam as 2.2 kJ/kg K. |
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Answer» Mass of steam to be produced, m = 4.4 kg Pressure of steam, p = 6 bar Temperature of steam, tsup = 250°C Temperature of water = 30°C Specific heat of steam, cps = 2.2 kJ/kg At 6 bar, 250°C : From steam tables, ts = 158.8°C, hf = 670.4 kJ/kg, hfg = 2085 kJ/kg Enthalpy of 1 kg superheated steam reckoned from 0°C, hsup = hf + hfg + cps (Tsup – Ts ) = 670.4 + 2085 + 2.2(250 – 158.8) = 2956 kJ Amount of heat already with 1 kg of water = 1 × 4.18 × (30 – 0) = 125.4 kJ Net amount of heat required to be supplied per kg = 2956 – 125.4 = 2830.6 kJ Total amount of heat required = 4.4 × 2830.6 = 12454.6 kJ. |
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