Thermodynamics: An Engineering Approach
Thermodynamics: An Engineering Approach
8th Edition
ISBN: 9780073398174
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
bartleby

Concept explainers

bartleby

Videos

Textbook Question
Book Icon
Chapter 2.8, Problem 74P

An oil pump is drawing 44 kW of electric power while pumping oil with ρ = 860 kg/m3 at a rate of 0.1 m3/s. The inlet and outlet diameters of the pipe are 8 cm and 12 cm, respectively. If the pressure rise of oil in the pump is measured to be 500 kPa and the motor efficiency is 90 percent, determine the mechanical efficiency of the pump.

FIGURE P2–73

Chapter 2.8, Problem 74P, An oil pump is drawing 44 kW of electric power while pumping oil with  = 860 kg/m3 at a rate of 0.1

Expert Solution & Answer
Check Mark
To determine

The mechanical efficiency of the pump.

Answer to Problem 74P

The mechanical efficiency of the pump is 91.8%_.

Explanation of Solution

Calculate the rate at which mechanical energy of fluid supplied to the pump.

ΔE˙mech,fluid=m˙(emech,outemech,in)=m˙((Pv)2+V222(Pv)1V122)=V˙((P2P1)+ρ(V22V122)) (I)

Here, the mechanical energy of water inlet and outlet are emech,in and emech,out, mass flow rate of water is m˙, Pressure of the pump at inlet and exit is P1, P2, density of the water is ρ, volume flow ate of water is V˙, velocity at inlet and exit of the pump is V1 and V2 respectively.

Calculate the velocity of the pump at inlet.

V1=V˙A1=V˙π4D12 (II)

Here, diameter of the pipe at inlet is D1.

Calculate the velocity of the pump at exit.

V2=V˙A2=V˙π4D22 (III)

Here, diameter of the pipe at exit is D2.

Calculate the useful pumping power.

W˙pump,u=ΔE˙mech,fluid (IV)

Calculate the shaft power.

W˙pump,shaft=ηmotorW˙electric (V)

Here, the efficiency of motor is ηmotor and electric power is W˙electric.

Calculate the mechanical efficiency of the pump.

ηpump=W˙pump,uW˙pump,shaft×100% (VI)

Conclusion:

Substitute 0.1m3/s for V˙, 500kN/m2 for P2P1, 860kg/m3 for ρ, 8.84m/s for V2, and 19.9 m/s for V1 in Equation (I).

ΔE˙mech,fluid=0.1m3/s((500kN/m2)+860kg/m3((8.84m/s)2(19.9m/s)22))=0.1m3/s((500kN/m2)+860kg/m3((8.84m/s)2(19.9m/s)22(1kN1000kgm/s2))(1kW1kNm/s))=36.3kW

Substitute 0.1m3/s for V˙ and 8 cm for D1 in Equation (II).

V1=0.1m3/sπ4(8cm)2=0.1m3/sπ4(8cm×1m100cm)2=19.9m/s

Substitute 0.1m3/s for V˙ and 12 cm for D2 in Equation (III).

V2=0.1m3/sπ4(12cm)2=0.1m3/sπ4(12cm×1m100cm)2=8.84m/s

Substitute 36.3 kW for ΔE˙mech,fluid in Equation (IV).

W˙pump,u=36.3kW

Substitute 0.90 for ηmotor and 44 kW for W˙electric in Equation (V).

W˙pump,shaft=(0.90)(44kW)=39.6kW

Substitute 39.6 kW for W˙pump,shaft and 36.3 kW for W˙pump,u in Equation (VI).

ηpump=36.3kW39.6kW×100%=0.918×100%=91.8%

Thus, the mechanical efficiency of the pump is 91.8%_.

Want to see more full solutions like this?

Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Students have asked these similar questions
2. Read the following Vernier caliper measurements. (The scales have been enlarged for easier reading.) The Vernier caliper is calibrated in metric units. (a) 0 1 2 3 4 5 سلسلسله (b) 1 2 3 4 5 6 سلسل (c) 1 23456 (d) 1 2 3 4 5 6 سلسلس
Explain why on the interval 0<x<1000 mm and 1000<x<2000mm, Mt is equal to positive 160 Nm, but at x= 0mm and x=1000mm Mt is equal to -160 Nm (negative value!). What is the reason for the sign change of Mt?
20 3. 2-233 2520 Тр Gears 1079 A pair of helical gears consist of a 20 teeth pinion meshing with a 100 teeth gear. The pinion rotates at Ta 720 r.p.m. The normal pressure angle is 20° while the helix angle is 25°. The face width is 40 mm and the normal module is 4 mm. The pinion as well as gear are made of steel having ultimate strength of 600 MPa and heat treated to a surface hardness of 300 B.H.N. The service factor and factor of safety are 1.5 and 2 respectively. Assume that the velocity factor accounts for the dynamic load and calculate the power transmitting capacity of the gears. [Ans. 8.6 kW

Chapter 2 Solutions

Thermodynamics: An Engineering Approach

Ch. 2.8 - Prob. 11PCh. 2.8 - At a certain location, wind is blowing steadily at...Ch. 2.8 - A water jet that leaves a nozzle at 60 m/s at a...Ch. 2.8 - Prob. 14PCh. 2.8 - Prob. 15PCh. 2.8 - Consider a river flowing toward a lake at an...Ch. 2.8 - When is the energy crossing the boundaries of a...Ch. 2.8 - Consider an automobile traveling at a constant...Ch. 2.8 - A gas in a pistoncylinder device is compressed,...Ch. 2.8 - A room is heated by an iron that is left plugged...Ch. 2.8 - A room is heated as a result of solar radiation...Ch. 2.8 - Prob. 23PCh. 2.8 - A small electrical motor produces 5 W of...Ch. 2.8 - Prob. 25PCh. 2.8 - 2–26C Lifting a weight to a height of 20 m takes...Ch. 2.8 - Prob. 27PCh. 2.8 - Prob. 28PCh. 2.8 - Prob. 29PCh. 2.8 - Prob. 30PCh. 2.8 - Prob. 31PCh. 2.8 - Prob. 32PCh. 2.8 - Prob. 33PCh. 2.8 - A ski lift has a one-way length of 1 km and a...Ch. 2.8 - The engine of a 1500-kg automobile has a power...Ch. 2.8 - Prob. 36PCh. 2.8 - What are the different mechanisms for transferring...Ch. 2.8 - On a hot summer day, a student turns his fan on...Ch. 2.8 - Prob. 39PCh. 2.8 - A vertical pistoncylinder device contains water...Ch. 2.8 - At winter design conditions, a house is projected...Ch. 2.8 - A water pump increases the water pressure from 15...Ch. 2.8 - Prob. 43PCh. 2.8 - Prob. 44PCh. 2.8 - A university campus has 200 classrooms and 400...Ch. 2.8 - Prob. 46PCh. 2.8 - Consider a room that is initially at the outdoor...Ch. 2.8 - Prob. 48PCh. 2.8 - 2-49 The 60-W fan of a central heating system is...Ch. 2.8 - Prob. 50PCh. 2.8 - An escalator in a shopping center is designed to...Ch. 2.8 - Prob. 52PCh. 2.8 - How is the combined pumpmotor efficiency of a pump...Ch. 2.8 - Prob. 54PCh. 2.8 - Can the combined turbinegenerator efficiency be...Ch. 2.8 - Consider a 2.4-kW hooded electric open burner in...Ch. 2.8 - Prob. 57PCh. 2.8 - Prob. 58PCh. 2.8 - Prob. 59PCh. 2.8 - A geothermal pump is used to pump brine whose...Ch. 2.8 - Prob. 62PCh. 2.8 - Prob. 63PCh. 2.8 - The water in a large lake is to be used to...Ch. 2.8 - A 7-hp (shaft) pump is used to raise water to an...Ch. 2.8 - At a certain location, wind is blowing steadily at...Ch. 2.8 - Reconsider Prob. 265. Using appropriate software,...Ch. 2.8 - Water is pumped from a lake to a storage tank 15 m...Ch. 2.8 - Prob. 69PCh. 2.8 - A hydraulic turbine has 85 m of elevation...Ch. 2.8 - Prob. 71PCh. 2.8 - Water is pumped from a lower reservoir to a higher...Ch. 2.8 - Prob. 73PCh. 2.8 - An oil pump is drawing 44 kW of electric power...Ch. 2.8 - How does energy conversion affect the environment?...Ch. 2.8 - What is acid rain? Why is it called a rain? How do...Ch. 2.8 - Why is carbon monoxide a dangerous air pollutant?...Ch. 2.8 - What is the greenhouse effect? How does the excess...Ch. 2.8 - What is smog? What does it consist of? How does...Ch. 2.8 - Prob. 80PCh. 2.8 - Consider a household that uses 14,000 kWh of...Ch. 2.8 - When a hydrocarbon fuel is burned, almost all of...Ch. 2.8 - Prob. 83PCh. 2.8 - A typical car driven 20,000 km a year emits to the...Ch. 2.8 - What are the mechanisms of heat transfer?Ch. 2.8 - Which is a better heat conductor, diamond or...Ch. 2.8 - How does forced convection differ from natural...Ch. 2.8 - What is a blackbody? How do real bodies differ...Ch. 2.8 - Define emissivity and absorptivity. What is...Ch. 2.8 - Does any of the energy of the sun reach the earth...Ch. 2.8 - The inner and outer surfaces of a 5-m 6-m brick...Ch. 2.8 - The inner and outer surfaces of a 0.5-cm-thick 2-m...Ch. 2.8 - Reconsider Prob. 292. Using appropriate software,...Ch. 2.8 - Prob. 94PCh. 2.8 - Prob. 95PCh. 2.8 - Prob. 96PCh. 2.8 - Prob. 97PCh. 2.8 - For heat transfer purposes, a standing man can be...Ch. 2.8 - Prob. 99PCh. 2.8 - Prob. 100PCh. 2.8 - A 1000-W iron is left on the ironing board with...Ch. 2.8 - A 7-cm-external-diameter, 18-m-long hot-water pipe...Ch. 2.8 - A thin metal plate is insulated on the back and...Ch. 2.8 - Reconsider Prob. 2103. Using appropriate software,...Ch. 2.8 - The outer surface of a spacecraft in space has an...Ch. 2.8 - Prob. 106PCh. 2.8 - A hollow spherical iron container whose outer...Ch. 2.8 - Consider a vertical elevator whose cabin has a...Ch. 2.8 - Consider a homeowner who is replacing his...Ch. 2.8 - Prob. 110RPCh. 2.8 - Prob. 111RPCh. 2.8 - Prob. 112RPCh. 2.8 - 2–113 The U.S. Department of Energy estimates that...Ch. 2.8 - Prob. 114RPCh. 2.8 - Prob. 115RPCh. 2.8 - Prob. 116RPCh. 2.8 - Prob. 117RPCh. 2.8 - Consider a TV set that consumes 120 W of electric...Ch. 2.8 - Water is pumped from a 200-ft-deep well into a...Ch. 2.8 - Prob. 120RPCh. 2.8 - Prob. 121RPCh. 2.8 - In a hydroelectric power plant, 65 m3/s of water...Ch. 2.8 - The demand for electric power is usually much...Ch. 2.8 - The pump of a water distribution system is powered...Ch. 2.8 - On a hot summer day, the air in a well-sealed room...Ch. 2.8 - Prob. 126FEPCh. 2.8 - A 2-kW electric resistance heater in a room is...Ch. 2.8 - A 900-kg car cruising at a constant speed of 60...Ch. 2.8 - Prob. 129FEPCh. 2.8 - Prob. 130FEPCh. 2.8 - Prob. 131FEPCh. 2.8 - A 2-kW pump is used to pump kerosene ( = 0.820...Ch. 2.8 - Prob. 133FEPCh. 2.8 - Prob. 134FEPCh. 2.8 - Prob. 135FEPCh. 2.8 - Prob. 136FEPCh. 2.8 - Prob. 137FEPCh. 2.8 - Heat is transferred steadily through a...Ch. 2.8 - The roof of an electrically heated house is 7 m...

Additional Engineering Textbook Solutions

Find more solutions based on key concepts
1.2 Explain the difference between geodetic and plane surveys,

Elementary Surveying: An Introduction To Geomatics (15th Edition)

What types of coolant are used in vehicles?

Automotive Technology: Principles, Diagnosis, And Service (6th Edition) (halderman Automotive Series)

The ____________ is always transparent.

Web Development and Design Foundations with HTML5 (8th Edition)

How does a computers main memory differ from its auxiliary memory?

Java: An Introduction to Problem Solving and Programming (8th Edition)

Knowledge Booster
Background pattern image
Mechanical Engineering
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.
Similar questions
SEE MORE QUESTIONS
Recommended textbooks for you
Text book image
Elements Of Electromagnetics
Mechanical Engineering
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Oxford University Press
Text book image
Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:9780134319650
Author:Russell C. Hibbeler
Publisher:PEARSON
Text book image
Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:9781259822674
Author:Yunus A. Cengel Dr., Michael A. Boles
Publisher:McGraw-Hill Education
Text book image
Control Systems Engineering
Mechanical Engineering
ISBN:9781118170519
Author:Norman S. Nise
Publisher:WILEY
Text book image
Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:9781337093347
Author:Barry J. Goodno, James M. Gere
Publisher:Cengage Learning
Text book image
Engineering Mechanics: Statics
Mechanical Engineering
ISBN:9781118807330
Author:James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:WILEY
Fluid Mechanics - Viscosity and Shear Strain Rate in 9 Minutes!; Author: Less Boring Lectures;https://www.youtube.com/watch?v=_0aaRDAdPTY;License: Standard youtube license