Problem sheet 3- ans PDF

Preview

Summary

Download Problem sheet 3- ans PDF

Description

Thermodynamics

EG-161

Problem Sheet 3

PROBLEMS for Thermodynamics EG-161 Sheet 3 3-1 Complete the following table for H20: T(ºC)

P(kPa) 325

160 80

h(kJ/kg)

x 0.4

Phase description

1682 950 500 800

Question 2.28 T(ºC) P(kPa) [136.30] 325 [617.8] 160 [179.91] 950 80 500 [350] 800

0.0 3161.7

h(kJ/kg)

[

x 0.4

Phase description

[1435.57]

1682

[0.469]

[Saturated mixture]

[762.81] [334.91]

0.0 [---]

[Saturated liquid] [Compressed liquid]

3161.7

[---]

[Superheated vapour]

[Saturated mixture]

3-2 Water is boiled at 1 atm pressure in a 20-cm-internal-diameter stain- less steel pan on an electric range. If it is observed that the water level in the pan drops by 10 cm in 45 min, determine the rate of heat transfer to the pan. [3.93 kW]

3-3 A rigid tank with a volume of 2.5 m3 contains 5 kg of saturated liquid-vapour mixture of water at 75ºC. Now the water is slowly heated. Determine the temperature at which the liquid in the tank is completely vaporised. Also, show the process on a T-v diagram with respect to saturation lines. [140.7 °C]

Thermodynamics

EG-161

Problem Sheet 3

3-4 A piston-cylinder device contains 0.1 m3 of liquid water and 0.9 m3 of water vapour in equilibrium at 800 kPa. Heat is transferred at constant pressure until the temperature reaches 350ºC. (a) What is the initial temperature of the water? (b) Determine the total mass of the water. (c) Calculate the final volume. (d) Show the process on a P-v diagram with respect to saturation lines. [(a) 170.41 °C (b) 93.43 kg (c) 33.1 m³]

Thermodynamics

EG-161

Problem Sheet 3

3-5 A piston-cylinder device contains 0.8 kg of steam at 300ºC and 1 MPa. Steam is cooled at constant pressure until one-half of the mass condenses. (a) Show the process on a T-v diagram. (b) Find the final temperature. (c) Determine the volume change. [(b) 179.91 °C (c) –0.128 m³]

Thermodynamics

EG-161

Problem Sheet 3

3-6 The pressure in an automobile tire depends on the temperature of the air in the tire. When the air temperature is 25ºC, the pressure gage reads 210 kPa. If the volume of the tire is 0.025 m3, determine the pressure rise in the tire when the air temperature in the tire rises to 50ºC. Also, determine the amount of air that must be bled off to restore pressure to its original value at this temperature. Assume the atmospheric pressure to be 100 kPa. [26 kPa, 0.0070 kg]

Thermodynamics

EG-161

Problem Sheet 3

3-7 A 1-m3 tank containing air at 25ºC and 500 kPa is connected through a valve to another tank containing 5 kg of air at 35ºC and 200 kPa. Now the valve is opened, and the entire system is allowed to reach thermal equilibrium with the surroundings, which are at 20ºC. Determine the volume of the second tank and the final equilibrium pressure of air. [2.21 m³, 284.1 kPa]

Thermodynamics

EG-161

Problem Sheet 3

3-8 A 4-L rigid tank contains 2 kg of saturated liquid-vapour mixture of water at 50ºC. The water is now slowly heated until it exists in a single phase. At the final state, will the water be in the liquid phase or the vapour phase? What would your answer be if the volume of the tank were 400 L instead of 4 L? [4L liquid 400L vapour]

3-9 A 0.5-m3 rigid tank containing hydrogen at 20ºC and 600 kPa is connected by a valve to another 0.5-m3 rigid tank that holds hydrogen at 30ºC and 150 kPa. Now the valve is opened and the system is allowed to reach thermal equilibrium with the surroundings, which are at 15ºC. Determine the final pressure in the tank. [365.8 kPa]...