Ask Question
3 September, 15:33

2. Air at a temperature of 20 ºC passes through a pipe with a constant velocity of 40 m/s. The pipe goes through a heat exchanger in which hot gases outside the pipe heat up the air to 820 ºC. It then enters a turbine with a velocity of 40 m/s and expands till the temperature falls to 620 ºC. The air stream loses 4.3 kW heat in the turbine. If the air flow rate is 2.5 kg/s, calculate (a) How much heat is transferred to the air in the heat exchanger. (b) The power output of the turbine.

+3
Answers (1)
  1. 3 September, 15:54
    0
    a) Q = 1436 kW

    b) P ≈ 776 kW

    Explanation:

    Let's begin by listing out the given parameters:

    T1 = 20 °C, u = 40 m/s, T2 = 820 °C, P = 4.3 kW, m = 2.5 kg/s, T3 = 510 °C, V1 = 40 m/s,

    V2 = 40 m/s, V3 = 55 m/s, ṁ = 2.5 kg/s

    To solve the question, we make this assumption that the size of the pipe is constant

    a) No change in velocity implies that heat added is isochoric

    Q = m * C * ΔT

    Cv of air at 300 K (≈20 °C) = 0.718

    Q = 2.5 * 0.718 * (820 - 20)

    Q = 1436 kW

    b) P = ṁ * Cp * ΔT + ṁ * (V2² - V3²) : 2000] - Ql

    V2² - V3² = 55² - 40² = 1425

    ΔT = T2 - T3 = 820 - 510 = 310 °C

    Cp of air at 300 K (≠20 °C) = 1.005 kJ/kgK

    Ql = 4.3 kW

    P = 2.5 * (1.005 * 310) + 2.5 * (1425 : 2000) - 4.3

    P = 778.875 + 1.78125 - 4.3 = 776.35625

    P ≈ 776 kW
Know the Answer?
Not Sure About the Answer?
Find an answer to your question ✅ “2. Air at a temperature of 20 ºC passes through a pipe with a constant velocity of 40 m/s. The pipe goes through a heat exchanger in which ...” in 📘 Physics if you're in doubt about the correctness of the answers or there's no answer, then try to use the smart search and find answers to the similar questions.
Search for Other Answers