EBK THERMODYNAMICS: AN ENGINEERING APPR
9th Edition
ISBN: 8220106796979
Author: CENGEL
Publisher: YUZU
expand_more
expand_more
format_list_bulleted
Videos
Textbook Question
Chapter 2.8, Problem 39P
On a hot summer day, a student turns his fan on when he leaves his room in the morning. When he returns in the evening, will the room be warmer or cooler than the neighboring rooms? Why? Assume all the doors and windows are kept closed.
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
Consider a heat transfer situation. Heat flows from the hot item or area to the cold item or area. Describe this in terms of spontaneity.
3. A classroom that normally contains 40 people is to be air-conditioned with window air-conditioning units of 5-kW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of about 360 kJ/h. There are 10 light bulbs in the room, each with a rating of 100 W. The rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kJ/h. If the room air is to be maintained at a constant temperature of 210C, determine the number of window air-conditioning units required. draw a figure also, and explain each step by step solution.
Calculate the amount of energy (in BTU) required to heat the air in a house 26 ft by 29 ft by 42 ft from 21 to 106 °F. The density of air is 0.08 lb/ft³.
Chapter 2 Solutions
EBK THERMODYNAMICS: AN ENGINEERING APPR
Ch. 2.8 - What is the difference between the macroscopic and...Ch. 2.8 - What is total energy? Identify the different forms...Ch. 2.8 - List the forms of energy that contribute to the...Ch. 2.8 - How are heat, internal energy, and thermal energy...Ch. 2.8 - What is mechanical energy? How does it differ from...Ch. 2.8 - Portable electric heaters are commonly used to...Ch. 2.8 - Natural gas, which is mostly methane CH4, is a...Ch. 2.8 - Consider the falling of a rock off a cliff into...Ch. 2.8 - Electric power is to be generated by installing a...Ch. 2.8 - The specific kinetic energy of a moving mass is...
Ch. 2.8 - Determine the specific kinetic energy of a mass...Ch. 2.8 - Calculate the total potential energy, in Btu, of...Ch. 2.8 - Determine the specific potential energy, in kJ/kg,...Ch. 2.8 - An object whose mass is 100 kg is located 20 m...Ch. 2.8 - A water jet that leaves a nozzle at 60 m/s at a...Ch. 2.8 - Consider a river flowing toward a lake at an...Ch. 2.8 - At a certain location, wind is blowing steadily at...Ch. 2.8 - What is the caloric theory? When and why was it...Ch. 2.8 - In what forms can energy cross the boundaries of a...Ch. 2.8 - What is an adiabatic process? What is an adiabatic...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 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 - A gas in a pistoncylinder device is compressed,...Ch. 2.8 - A small electrical motor produces 5 W of...Ch. 2.8 - A car is accelerated from rest to 85 km/h in 10 s....Ch. 2.8 - A construction crane lifts a prestressed concrete...Ch. 2.8 - Determine the torque applied to the shaft of a car...Ch. 2.8 - A spring whose spring constant is 200 lbf/in has...Ch. 2.8 - How much work, in kJ, can a spring whose spring...Ch. 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 - A damaged 1200-kg car is being towed by a truck....Ch. 2.8 - As a spherical ammonia vapor bubble rises in...Ch. 2.8 - A steel rod of 0.5 cm diameter and 10 m length is...Ch. 2.8 - What are the different mechanisms for transferring...Ch. 2.8 - For a cycle, is the net work necessarily zero? For...Ch. 2.8 - On a hot summer day, a student turns his fan on...Ch. 2.8 - Water is being heated in a closed pan on top of a...Ch. 2.8 - An adiabatic closed system is accelerated from 0...Ch. 2.8 - A fan is to accelerate quiescent air to a velocity...Ch. 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 - The lighting needs of a storage room are being met...Ch. 2.8 - A university campus has 200 classrooms and 400...Ch. 2.8 - Consider a room that is initially at the outdoor...Ch. 2.8 - An escalator in a shopping center is designed to...Ch. 2.8 - Consider a 2100-kg car cruising at constant speed...Ch. 2.8 - Prob. 51PCh. 2.8 - What is mechanical efficiency? What does a...Ch. 2.8 - How is the combined pumpmotor efficiency of a pump...Ch. 2.8 - Can the combined turbinegenerator efficiency be...Ch. 2.8 - Consider a 2.4-kW hooded electric open burner in...Ch. 2.8 - The steam requirements of a manufacturing facility...Ch. 2.8 - Reconsider Prob. 256E. Using appropriate software,...Ch. 2.8 - A 75-hp (shaft output) motor that has an...Ch. 2.8 - Prob. 59PCh. 2.8 - An exercise room has six weight-lifting machines...Ch. 2.8 - A room is cooled by circulating chilled water...Ch. 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 - A geothermal pump is used to pump brine whose...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 lower reservoir to a higher...Ch. 2.8 - An 80-percent-efficient pump with a power input of...Ch. 2.8 - Water is pumped from a lake to a storage tank 15 m...Ch. 2.8 - Large wind turbines with a power capacity of 8 MW...Ch. 2.8 - A hydraulic turbine has 85 m of elevation...Ch. 2.8 - The water behind Hoover Dam in Nevada is 206 m...Ch. 2.8 - An oil pump is drawing 44 kW of electric power...Ch. 2.8 - A wind turbine is rotating at 15 rpm under steady...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 - 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. 82PCh. 2.8 - A typical car driven 20,000 km a year emits to the...Ch. 2.8 - Prob. 84PCh. 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 - Some engineers have developed a device that...Ch. 2.8 - Consider a classroom for 55 students and one...Ch. 2.8 - Consider a homeowner who is replacing his...Ch. 2.8 - Prob. 111RPCh. 2.8 - The U.S. Department of Energy estimates that...Ch. 2.8 - A typical household pays about 1200 a year on...Ch. 2.8 - Prob. 114RPCh. 2.8 - Prob. 115RPCh. 2.8 - Prob. 116RPCh. 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 - Consider a vertical elevator whose cabin has a...Ch. 2.8 - Prob. 120RPCh. 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 - Prob. 124RPCh. 2.8 - A 2-kW electric resistance heater in a room is...Ch. 2.8 - Prob. 126FEPCh. 2.8 - A 75-hp compressor in a facility that operates at...Ch. 2.8 - On a hot summer day, the air in a well-sealed room...Ch. 2.8 - A fan is to accelerate quiescent air to a velocity...Ch. 2.8 - A 900-kg car cruising at a constant speed of 60...Ch. 2.8 - Prob. 131FEPCh. 2.8 - Prob. 132FEPCh. 2.8 - A 2-kW pump is used to pump kerosene ( = 0.820...Ch. 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
A number of common substances are
Some of these materials exhibit characteristics of both solid and fluid beha...
Fox and McDonald's Introduction to Fluid Mechanics
For the beam loading of Figure P334, draw the complete shearing force and bending moment diagrams, and determin...
Machine Elements in Mechanical Design (6th Edition) (What's New in Trades & Technology)
Determine the velocity of block D if end A of the rope is pulled down with a speed of vA = 3 m/s.
Engineering Mechanics: Dynamics (14th Edition)
3.3 It is known that a vertical force of 200 lb is required to remove the nail at C from the board. As the nail...
Vector Mechanics for Engineers: Statics
What types of coolant are used in vehicles?
Automotive Technology: Principles, Diagnosis, and Service (5th Edition)
CONCEPT QUESTIONS
15.CQ3 The ball rolls without slipping on the fixed surface as shown. What is the direction ...
Vector Mechanics for Engineers: Statics and Dynamics
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.Similar questions
- On a mild Saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23°C. At noon the furnace is turned off, and the people go home. The temperature outside is a constant 14°C for the rest of the afternoon. If the time constant for the building is 3 hr, when will the temperature inside the building reach 19°C? If some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 19°C? If the time constant for the building is 3 hr, the temperature inside the building will reach 19°C about hr after noon. (Round to the nearest tenth as needed.) If the time constant for the building drops to 2 hr, the temperature inside the building will reach 19°C about (Round to the nearest tenth as needed.) hr after noon. Carrow_forwardA 12-by-12 in. open pan containing water at 140 °F is placed in the exact center of a 16-by-20 ft room having a ceiling temperature of 75°F. If the distance from the water surface to the ceiling is 10 ft and the ceiling is painted with an oil paint, what is the net radiant-heat exchange between the water surface and the ceiling?arrow_forwardHelparrow_forward
- A PUC is considering a subsidy program to encourage consumers to install improved insulation in homes as a way of reducing the amount of electricity consumed and reduce air pollution. The insulation program would cost $1,500,000 and would save 5,000 MWh of power. Assuming that natural gas is used to generate the electricity and 1 MWh produces 1,135 pounds of carbon dioxide. What is the cost of this program per ton of carbon dioxide?arrow_forwardWhat is a K system?arrow_forwardConsider two houses that are identical in size. House 1 has outside walls that were built using a double layer of brick. House 2 has outside walls that were built using a single layer of wood. Discuss and explain which house will be more energy efficient?arrow_forward
- If the LHV of wood logs is 16 MJ/kg, how much energy is available for 2 kg of wood logs? If I burn all wood logs, what is the maximum energy in the heat I could obtain? If 30% of heat can be changed to electricity, how much electricity will be generated? If the heating value (LHV) of dry wood is 20 MJ/kg, what is the maximum energy 20 tonnes of wood could provide? If 60 % of the heat in wood could be transferred, how much heat can be transferred? If the heating value of coal is 40 MJ/kg, how much energy is available for 10 tonnes of coal? If I burn wood logs (LHV =16 MJ) to obtain the same amount of heat, how much (in tonne) of wood logs do I need to burn?arrow_forwardC- The average specific heat (Cp) of the human body is 3.6 kJ/kg °C. If the body temperature of a 70-kg man rises from 37°C to 39°C during strenuous exercise, determine the increase in the thermal energy content of the body as a result of this rise in body temperature. If the man dresses more clothes what would happen, will he gain or loss heat in which mechanism?arrow_forwardЕxample:- In a warm room, a naked resting person has a skin temperature of 33°C If the room temperature is 29°C and the body surface area is 1.5m2 .What is the rate of heat loss due to convection if Kc=7.1 watt/m2 .k?arrow_forward
- The fin efficiency is defined as the ratio of the actual heat transfer from the fin to a. The heat transfer from an equivalent fin which is infinitely long b. The heat transfer through the base area of the same fin c. The heat transfer from the same fin with an adiabatic tip d. The heat transfer from the same fin if the temperature along the entire length of the fin is the same as the base temperaturearrow_forwardQ.1 (40 pts) A chef (cook) in a restaurant is cooking a special bread. The bread is (L x L) cooked on rock and the rock is (L x L) heated by flames from the bottom uniformly. The bottom of the bread is in contact with the rock. The contact resistance between the rock and the bread is R-0,2°C/W. The top and the sides of the bread is in contact with a wooden lid (cover). After the bread is cooked the chef takes it from the rock,cools it down to 10°C in the refrigerator and then puts it back on the rock to heat it. The flame temperature is 900°C. If the the bottom of the bread reaches 260°C, it burns. For how long can the chef heat the bread without burning it? Use the below values. HINT: Wood is a bad heat conductor. Rock: t,- 8 cm k,-10W/mk L=22 cm Bread: t=2 cm k=50W/mK L=22 cm p,=800kg/m3 C=3000J/kgK WOODEN LID (COVER) BREAD ROCK FLAMESarrow_forwardYou want to heat a house on a very cold day as shown in the figure. To do this, you want to use photovoltaic panels as an energy source. It would be about using 15 panels each with an area of 1.5 m2. These panels would be connected to an electrical resistance that would heat the house as shown in the figure. The house is losing heat through the walls and ceiling as shown in the figure. The panels are receiving solar radiation at a rate of 800 W / m2 and if their efficiency is 15%. How much will the temperature of the house rise after an hour? The house is hermetically sealed. Assume that the specific heats of air, cv and cp, are constant as shown in the figure. sol = sun fuga = leakage aire = airarrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
Refrigeration and Air Conditioning Technology (Mi...Mechanical EngineeringISBN:9781305578296Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill JohnsonPublisher:Cengage Learning
Principles of Heat Transfer (Activate Learning wi...
Mechanical Engineering
ISBN:9781305387102
Author:Kreith, Frank; Manglik, Raj M.
Publisher:Cengage Learning
Refrigeration and Air Conditioning Technology (Mi...
Mechanical Engineering
ISBN:9781305578296
Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher:Cengage Learning
Heat Transfer – Conduction, Convection and Radiation; Author: NG Science;https://www.youtube.com/watch?v=Me60Ti0E_rY;License: Standard youtube license