Explanation Consider the air flows at steady state through one inlet and one exit system (pipe and duct flow). Hence, the inlet and exit mass flow rates are equal. m ˙ 1 = m ˙ 2 = m ˙ 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 (I) 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 air flows at steady state through the system. Hence, the rate of change in net energy of the system becomes zero. Δ E ˙ system = 0 The heat is added to the air. Neglect the heat transfer at the outlet, work transfer, kinetic and potential energies. The Equations (I) reduced as follows. [ 0 + Q ˙ 1 + m ˙ ( h 1 + 0 + 0 ) ] − [ 0 + 0 + m ˙ ( h 2 + 0 + 0 ) ] = 0 Q ˙ 1 + m ˙ h 1 − m ˙ h 2 = 0 Q ˙ 1 = m ˙ h 2 − m ˙ h 1 Q ˙ 1 = m ˙ ( h 2 − h 1 ) (II) The change in enthalpy 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 . Substitute c p ( T 2 − T 1 ) for h 2 − h 1 in Equation (II). Q ˙ 1 = m ˙ [ c p ( T 2 − T 1 ) ] = m ˙ c p ( T 2 − T 1 ) (III) Rearrange the Equation (III) to obtain the exit temperature ( T 2 ) . Q ˙ 1 m ˙ c p = T 2 − T 1 T 2 = Q ˙ 1 m ˙ c p + T 1 (IV) Write the formula for mass flow rate of air ( m ˙ )

9th Edition

ISBN: 9781307573022

Author: CENGEL

Publisher: MCG/CREATE

See similar textbooks

Videos

Question

Chapter 5.5, Problem 96P

To determine

The average temperature at which the air leaves the hollow core.

Expert Solution & Answer

Want to see the full answer?

Check out a sample textbook solution

See solution

Chapter 5.5, Problem 95P

Chapter 5.5, Problem 97P

Students have asked these similar questions

Five hundred kilograms per hour of steam moves a turbine. The steam enters the turbine at 44 atm and 450°C with a speed linear 60 m/s, and exits at a point 5 m below the inlet, at pressure atmospheric and at a speed of 360 m/s. The turbine provides work on the shaft with a rating of 70 kW, and the heat loss in the turbine is estimated at 104 kcal/h. Calculate the variation in specific enthalpy associated with the process.

Water at the initial pressure of 1 atm and temperature of 15C is flowing through a pump. Final pressure of water is 900 kPa at the outlet. Water enters through a 1-cm-diameter opening and exits through a 2.5-cm- diameter opening. Determine the velocity of the water at the inlet and outlet when the mass flow rate through the pump is 0.5 kg/s.

In a boiler of a steam power plant the incoming water is heated to steam by hot gas flowing around the tube. The hot gas is produced by combustion of coal. Consider the pressure of water flowing through the tube to be 4 MPa. Water enters the tube at a velocity of 0.1 m/s and a temperature of 50 °C. The tube diameter is 2.5 cm. The hot gas flowing around the tube is at 1000 °C. The water needs to reach the saturation temperature of 250 °C. Assuming bulk mean temperature of water to be 600 °C, and the determine the average convective heat transfer coefficient to be 80 W/m².K, determine what should be the length of the pipe.

Chapter 5 Solutions

THERMODYNAMICS-SI ED. EBOOK >I<

Ch. 5.5 - Name four physical quantities that are conserved...Ch. 5.5 - Define mass and volume flow rates. How are they...Ch. 5.5 - Does the amount of mass entering a control volume...Ch. 5.5 - Consider a device with one inlet and one outlet....Ch. 5.5 - The ventilating fan of the bathroom of a building...Ch. 5.5 - Air enters a 16-cm-diameter pipe steadily at 200...Ch. 5.5 - A steam pipe is to transport 200 lbm/s of steam at...Ch. 5.5 - A garden hose attached with a nozzle is used to...Ch. 5.5 - A steady-flow compressor is used to compress...Ch. 5.5 - Air enters the 1-m2 inlet of an aircraft engine at...

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.

The average temperature at which the air leaves the hollow core.

Solution Summary: The author calculates the energy rate balance equation for one inlet and one outlet system.

Videos

The average temperature at which the air leaves the hollow core.

Want to see the full answer?

Chapter 5 Solutions