To determine The mass flow rate of bleed steam required to operate the closed feed water unit. Explanation Draw the schematic diagram of the given close feed water heater as shown in Figure 1. Here, the hot and cold streams (comparatively) of fluids are mixed in a rigid mixing chamber (open feed water heater) and operates at steady state. Hence, the inlet and exit mass flow rates are equal. m ˙ 1 + m ˙ 2 = m ˙ 3 (I) Here, the mass flow rate of water is m ˙ 1 , the mass flow rate of bleed steam is m ˙ 2 , and the mass flow rate of mixed stream is m ˙ 3 . Write the general energy rate balance equation. E ˙ in − E ˙ out = Δ E ˙ system (I) Here, the rate of change of total energy in is E ˙ in , the rate of change of total energy out is E ˙ out , and the rate of change in net energy of the system is Δ E ˙ system . Consider the closed feed water system operates at steady state. Hence, the rate of change in net energy of the system becomes zero. Δ E ˙ system = 0 The Equation (I) is reduced as follows. E ˙ in − E ˙ out = 0 E ˙ in = E ˙ out (II) Refer Figure 1 and Equation (II). Neglect the heat transfer, work transfer, kinetic and potential energies. Write the energy rate balance equation for the given closed feed water system. m ˙ 1 h 1 + m ˙ 3 h 3 − m ˙ 3 w P,in = m ˙ 6 h 6 (III) From Figure 1. The mass flow rate at the state 6 is expressed as follows. m ˙ 6 = m ˙ 1 + m ˙ .3 Substitute m ˙ 1 + m ˙ 3 for m ˙ 6 in Equation (III) and rearrange it to obtain m ˙ 3 . m ˙ 1 h 1 + m ˙ 3 h 3 + m ˙ 3 w P,in = ( m ˙ 1 + m ˙ 3 ) h 6 m ˙ 1 h 1 + m ˙ 3 h 3 + m ˙ 3 w P,in = m ˙ 1 h 6 + m ˙ 3 h 6 m ˙ 3 h 3 + m ˙ 3 w P,in − m ˙ 3 h 6 = m ˙ 1 h 6 − m ˙ 1 h 1 m ˙ 3 ( h 3 + w P,in − h 6 ) = m ˙ 1 ( h 6 − h 1 ) m ˙ 3 = m ˙ 1 ( h 6 − h 1 ) h 3 + w P,in − h 6 (IV) Write the formula work input of the pump

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Chapter 10.9, Problem 44P

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The mass flow rate of bleed steam required to operate the closed feed water unit.

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Chapter 10.9, Problem 43P

Chapter 10.9, Problem 45P

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