Explanation The sensible heat generated by the total students is expressed as, Q ˙ gen,sensible = q ˙ gen,sensible × no .of students = q ˙ gen,sensible × 150 = 150 ( q ˙ gen,sensible ) (I) Here, the sensible heat generated by each student is q ˙ gen,sensible . The total sensible heat generated in the class room is expressed as, Q ˙ total,sensible = Q ˙ gen,sensible + Q ˙ lighting (II) Consider the class room as the imaginary duct and the chilled air passes through in it. The total sensible heat generated is transferred to the chilled air. And also the air flows at steady state. The mass flow rate of air ( m ˙ air ) is as follows. m ˙ 1 = m ˙ 2 = m ˙ air Write the energy rate balance equation for one inlet and one outlet system. { [ Q ˙ 1 + W ˙ 1 + m ˙ ( h 1 + V 1 2 2 + g z 1 ) ] − [ Q ˙ 2 + W ˙ 2 + m ˙ ( h 2 + V 2 2 2 + g z 2 ) ] } = Δ E ˙ system (III) Here, the rate of heat transfer is Q ˙ , the rate of work transfer is W ˙ , the enthalpy is h and the velocity is V , the gravitational acceleration is g , the elevation from the datum is z and the rate of change in net energy of the system is Δ E ˙ system ; the suffixes 1 and 2 indicates the inlet and outlet of the system. The system is at steady state. Hence, the rate of change in net energy of the system becomes zero. Δ E ˙ system = 0 Neglect the work transfer, potential and kinetic energies. The Equations (III) reduced as follows. [ Q ˙ 1 + 0 + m ˙ air ( h 1 + 0 + 0 ) ] − [ 0 + 0 + m ˙ air ( h 2 + 0 + 0 ) ] = 0 Q ˙ 1 + m ˙ air h 1 − m ˙ air h 2 = 0 Q ˙ 1 = m ˙ air ( h 2 − h 1 ) (II) The change in enthalpy ( h 2 − h 1 ) is expresses as follow. h 2 − h 1 = c p ( T 2 − T 1 ) Here, the specific heat is c p , the exit temperature is T 2 and the inlet temperature is T 1

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A substance with fixed chemical composition throughout is called a pure substance like water, air, and nitrogen. A pure substance does not have to be a single element or compound. A mixture of two or more phases of a pure substance is also a pure substan…

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Chapter 5.5, Problem 171RP

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The required flow rate of air, in kg/s that needs to be supplied to the room to keep the average temperature of the room as constant.

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Chapter 5.5, Problem 170RP

Chapter 5.5, Problem 172RP

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The required flow rate of air, in kg/s that needs to be supplied to the room to keep the average temperature of the room as constant.

Solution Summary: The author explains the required flow rate of air, in kg/s, that needs to be supplied to the room to keep the average temperature as constant. The total sensible heat generated in the class room is

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The required flow rate of air, in kg/s that needs to be supplied to the room to keep the average temperature of the room as constant.

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