Consider the mixing of 0.8 kg/s of hot water at 348 K and 1 kg/s of cool water at 298 K that is generating warm water. Assume no work is being done and the system is in steady state, but heat is lost at the rate of 30 kJ/s during this mixing. Find the temperature of the warm water flow stream? Assume Cp = 4.18 kJkg

Question

Conor Weeks

Engineering

14 March, 22:40

Consider the mixing of 0.8 kg/s of hot water at 348 K and 1 kg/s of cool water at 298 K that is generating warm water. Assume no work is being done and the system is in steady state, but heat is lost at the rate of 30 kJ/s during this mixing. Find the temperature of the warm water flow stream? Assume Cp = 4.18 kJkg

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Answers (1)

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Jax Andrews · Answer 1

T_warm = 47.22 C

Explanation:

Using energy balance for the system:

m_1*h_1 + m_2*h_2 = m_3*h3 ... Eq1

h_i = c_p. T_i ... Eq 2

m_1 + m_2 = m_3 ... steady flow system (Eq 3)

Substitute Eq 2 and Eq3 in Eq1

m_3 = 0.8 + 1 = 1.8 kg/s

(0.8) * (4.18) * (348-273) + (1) * (4.18) * (298-273) = 1.8 * 4.18 * T_3

T_3 = 355.3 / (1.8*4.18) = 47.22 C