Question

A heat exchanger produces dry steam at 100°C from feed water at 30°C at a rate of 1.5 kgs−1. The heat exchanger receives heat energy at a rate of 600 kW from the fuel used. The specific heat capacity of water is 4187 Jkg−1K−1 and its specific latent heat of vaporisation is 2257 Jkg−1.
i) Determine the heat energy received per kilogram of steam produced.

Answer 1

Answer on Question #60560-Engineering-Mechanical Engineering

A heat exchanger produces dry steam at 100 C from feed water at 30C at a rate of 1.5 kgs^-1. The heat exchanger receives heat energy at a rate of 600 kW from the fuel used. The specific heat capacity of water is 4187 Jkg^-1K^-1 and its specific latent heat of vaporisation is 2257 Jkg^-1.

i) Determine the heat energy received per kilogram of steam produced.

Solution

$$\frac{dm}{dt} = 1.5 \frac{kg}{s}$$ $$T_c = 30\,C$$ $$T_h = 100\,C$$ $$P = 600\,kW$$ $$C = 4187 \frac{J}{kg\,K}$$ $$L = 2257 \frac{J}{kg}$$

i)

$$Q = mC(T_h - T_c) + mL$$ $$dQ = C(T_h - T_c)dm + Ldm$$ $$\frac{dQ}{dm} = C(T_h - T_c) + L = 4187 \frac{J}{kg\,K} (100\,C - 30\,C) + 2257 \frac{J}{kg} = 295347 \frac{J}{kg}$$