homework 1 2018

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Question Description

make sure you do 2018 Provide a schematic diagram (sketch) of the problem configuration (if applicable). Specify the source of ANY equation used (equation number from text) and justify (where appropriate) the choice of the equation. Do not forget units/dimensions. Incorrect units/dimensions WILL result in reduced points (during grading) for the solution.

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EGR/MET432 : Thermo-Fluids II Spring 2016 Homework 1 Due date: 1/28/2016 (Thursday) (To be submitted at the beginning of the class meeting) 1) An insulated rigid container contains 2 kg of water at 150 kPa. The volume of the container is 1.6 m3. An electric resistance heater inside the container is now turned on and kept on until the pressure inside the container reaches 400 kPa. Calculate the a) Initial and final temperatures of water in the container b) Total amount of heat added during the heating process c) Change in entropy for the water (kJ/K) during the process o 2) Air enters an isentropic nozzle at 50 psia, 220 F and 15 ft/sec. At the nozzle exit, the pressure is 32 psia. Assume the specific heat ratio (k) to be 1.4. Calculate the nozzle exit velocity using a) Constant specific heats (approximate analysis) b) Variable specific heats (exact analysis). 3) Steam enters an adiabatic turbine at 6 MPa, 550 oC and 50 m/sec with a flow rate of 5.4 kg/sec. At the turbine exit, the flow conditions are 100 kPa, 150 oC and 160 m/sec. For the turbine, calculate the a) Power output from the turbine b) Isentropic efficiency of the turbine c) Draw a T-s diagram showing the actual and isentropic expansion processes (don’t forget to include the vapor dome) Note: Provide a schematic diagram (sketch) of the problem configuration (if applicable). Specify the source of ANY equation used (equation number from text) and justify (where appropriate) the choice of the equation. Do not forget units/dimensions. Incorrect units/dimensions WILL result in reduced points (during grading) for the solution. EGR 432 : Engineering Thermo-Fluids II Fall 2018 Homework 1 Due date: 9/6/2018 (Thursday) (To be submitted at the beginning of the class meeting) 1) An insulated piston-cylinder device contains 1.6 kg of water at 400 kPa and the volume of the water at this state is 0.6 m3. A 2000 W electric resistance heater inside the cylinder is then turned on and kept on, under constant pressure conditions, until the temperature inside the cylinder reaches 300 oC. Calculate the a) Total time the heater was on during the energy addition process b) Change in entropy (kJ/K) of the water during the heating process. 2) A rigid container (volume = 2.7 ft3) contains 0.3 lbm of air, initially at 30 psia. Heat is then added to the air until the pressure inside the container reaches 60 psia. Assume that there is negligible heat loss during the process. Using the approximate analysis (use 600 oF as the reference temperature for evaluating specific heats), calculate the a) Initial and final temperatures of air in the container b) Total amount of heat added (Btu) during the heating process c) Change in entropy for the air (Btu/oR) during the process 3) Air enters an isentropic nozzle at 360 kPa, 8 m/sec and 540 K. At the nozzle exit, the pressure is 90 kPa. Calculate the temperature and velocity of the airflow at the nozzle exit using a) Exact analysis (variable specific heats) b) Approximate analysis (constant specific heats; assume that the ratio of specific heats (k) for air is 1.4) 4) Steam enters an adiabatic turbine at 300 psia, 600 oF and 50 ft/sec with a flow rate of 12.5 lbm/sec. At the turbine exit, the flow conditions are 40 psia, 280 oF and 120 ft/sec. For the turbine, calculate the a) Power output (hp) b) Isentropic efficiency c) Draw a T-s diagram showing the actual and isentropic expansion processes (don’t forget to include the vapor dome) Note: Provide a schematic diagram (sketch) of the problem configuration (if applicable). Specify the source of ANY equation used (equation number from text) and justify (where appropriate) the choice of the equation. Do not forget units/dimensions. Incorrect units/dimensions WILL result in reduced points (during grading) for the solution. ...
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achiaovintel
School: UC Berkeley

hello, kindly find the attached solution. In case of any question feel free to ask and kindly remember to review my work. Thank you.

Running Head: ENGINEERING THERMO-FLUIDS 11

Engineering Thermo-Fluids II
Name:
Institution:
Instructor:
Date:

1

ENGINEERING THERMO-FLUIDS 11

2
Question 1

An insulated piston-cylinder device contains 1.6 kg of water at 400 kPa and the volume of the
water at this state is 0.6 m3. A 2000 W electric resistance heater inside the cylinder is then turned
on and kept on, under constant pressure conditions, until the temperature inside the cylinder
reaches 300 0 C. Calculate the:
a) Total time the heater was on during the energy addition process
Solution
P1 = P2 = 400KPa
V1 = 0.6m3
H = 2000W
T2 = 3000 C T2 = 300 + 273 = 573K
To find the total time the heater was on we assume water to be an ideal gas
The ideal gas equation
P1 V1 = mRT1

R = 0.4618

400 × 0.6 = 1.6 × 0.461 × T1
T1 = 324.826K
At constant pressure
Q = mCp (T2 − T1 )

Cp for water = 4.18

KJ
KgK

Q = mCp (T2 − T1 ) = H × t
t=

mCp (T2 − T1 ) 1.6 × 4.18(573 − 324.826)
=
= 0.8299sec
H
2000
𝐀𝐧𝐬𝐰𝐞𝐫: 𝐭 = 𝟎. 𝟖𝟐𝟗𝟗𝐬𝐞𝐜

ENGINEERING THERMO-FLUIDS 11

3

b) Change in entropy (kJ/K) of the water during the heating process.
T2
∆s = mCp ln ( )
T1
573
KJ
∆s = 1.6 × 4.18 × ln (
) = 3.8088
...

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