a) Explanation Write the expression to obtain the amount of steam added to the air in the heating section ( Δ ω ) . Δ ω = ω 3 − ω 2 (I) Here, specific humidity at in the humidified section is ω 3 and specific humidity at outlet condition is ω 2 . Conclusion: Refer Fig A-31, “Psychrometric chart at 1 atm total pressure” at inlet conditions of inlet temperature of outdoor air ( T 1 = 35 °F ) and relative humidity ( ϕ 1 = 50 % ) , write the values of enthalpy ( h 1 ) as 10.69 Btu / lbm dry air , specific humidity ( ω 1 ) of air entering as 0.002122 lbm H 2 O / lbm dry air . Refer Fig A-31, “Psychrometric chart at 1 atm total pressure” at outlet conditions, temperature of outdoor air ( T 2 = 65 °F ) and pressure ( P 2 = 14.7 psia ) , write the values of enthalpy ( h 2 ) as 17.93 Btu / lbm dry air and the value of ω 1 = ω 2 are same because the amount of water vapor in the air remains constant in the heating section. Refer Fig A-31, “Psychrometric chart at 1 atm total pressure” in the humidified section at temperature ( T 3 = 75 °F ) and relative humidity ( ϕ 3 = 55 % ) , write the values of enthalpy ( h 3 ) as 29 b) To determine The amount of heat transfer to the air in the heating section per unit mass of air.

8th Edition

ISBN: 8220100257056

Author: CENGEL

Publisher: YUZU

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Chapter 14.7, Problem 72P

To determine

The amount of steam added to the air in the heating section.

To determine

The amount of heat transfer to the air in the heating section per unit mass of air.

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Chapter 14.7, Problem 71P

Chapter 14.7, Problem 73P

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As shown in the figure below, moist air at T₁ = 36°C, 1 bar, and 35% relative humidity enters a heat exchanger operating at steady state with a volumetric flow rate of 10 m³/min and is cooled at constant pressure to 22°C. Ignoring kinetic and potential energy effects, determine: (a) the dew point temperature at the inlet, in °C. (b) the mass flow rate of moist air at the exit, in kg/min. (c) the relative humidity at the exit. (d) the rate of heat transfer from the moist air stream, in kW. (AV)1, T1 P₁ = 1 bar 11 = 35% 120 T₂=22°C P2 = 1 bar

Air at T₁-24°C, p₁-1 bar, 50% relative humidity enters an insulated chamber operating at steady state with a mass flow rate of 3 kg/min and mixes with a saturated moist air stream entering at T₂-7°C, p2-1 bar. A single mixed stream exits at T3-17°C, p3-1 bar. Neglect kinetic and potential energy effects Step 1 Your answer is correct. Determine mass flow rate of the moist air entering at state 2, in kg/min. m2 = 2.1 Hint kg/min Using multiple attempts will impact your score. 5% score reduction after attempt 2 Step 2 Determine the relative humidity of the exiting stream. Փ3 = i % Attempts: 1 of 3 used

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EBK THERMODYNAMICS: AN ENGINEERING APPR

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