Question

Carbon dioxide passing through a heat exchanger at a rate of 100kg/hr is cooled down from 800°C to 50°C. Write the steady flow energy equation. Assuming that the change in pressure, kinetic and potential energies and flow work interaction are negligible, determine the rate of heat removal. (Take C_p = 1.08Kj/kg-K)

Answer 1

Given data:

m_f = 100Kg/hr = 100/3600 Kg/sec = 1/36 Kg/sec

T₁ = 800°C

T₂ = 50°C

C_p = 1.08Kj/kg–K

Rate of heat removal = Q = ?

Now Applying SFEE

Q – W_S = m_f [(h₂ – h₁) + 1/2( V₂² –V₁²) + g(Z₂ – Z₁)]

Since change in pressure, kinetic and potential energies and flow work interaction are negligible, i.e.;

W_S = 1/2( V₂² –V₁²) = g(Z₂ – Z₁) = 0

Now

Q = m_f [(h₂ – h₁)] = m_f [C_P.d_T] = (1/36) × 1.08 (800 – 50)

Q = 22.5 KJ/sec