The cost of energy “vented out” by the fans in 1 h.
Answer to Problem 147RP
The cost of energy “vented out” by the fans in 1 h is
Explanation of Solution
Determine the density of air at the indoor conditions.
Here, the house maintain a pressure is
Determine interior volume of the house per hour
Here, the width of the house is
Determine the mass flow rate of air vented out.
Determine the rate of energy loss by the ventilating fans.
Here, the specific heat of air at room temperature is
Determine the amount of fuel energy loss by “vented out”.
Here, the fan takes time is
Determine the amount of cost of the heat “vented out” per hour.
Conclusion:
From the Table A-1, “Molar mass, gas constant, and critical-point properties” to obtain the value of gas constant of air as
From the Table A-2a, “Ideal-gas specific heats of various common gases” to obtain the value of specific heat of air at room temperature as
Substitute 92 kPa for
Substitute
Substitute
Substitute
Substitute
Substitute
Thus, the cost of energy “vented out” by the fans in 1 h is
Want to see more full solutions like this?
Chapter 6 Solutions
Package: Thermodynamics: An Engineering Approach With 2 Semester Connect Access Card
- It is well known that the power consumed by a compressor can be reduced by cooling the gas during compression. Inspired by this, somebody proposes to cool the liquid as it flows through a pump, in order to reduce the power consumption of the pump. Would you support this proposal? Explain.arrow_forwardConsider the energy generated by a TV set. What is a suitable choice for a thermal energy reservoir?arrow_forwardAn electric generator at a power plant produces energy by passing superheated steam from a high temperature container (reservoir), through a pipe connected to a series of fans, and then into a low temperature reservoir. As the steam passes across the blades of the fans some of the heat energy of the steam is transformed into mechanical energy, which turns the fans which in turn are connected to a generator, which in turn converts the mechanical energy into electrical energy. If the high temperature steam has a temperature of 201.9 K and the low temperature reservoir has a temperature of 154.1 K, what is the Carnot efficiency of this process?arrow_forward
- Requires Solution:Determine the power required providing 3 kw of colling at -10 degrees celcius while the surrounding air is at 24 degrees celcius. Answer: 0.39 kWarrow_forwardThe blades of a wind turbine turn a large shaft at a relatively slow speed. The rotational speed is increased by a gearbox that has an efficiency of 0.93. In turn, the gearbox output shaft drives an electric generator with an efficiency of 0.95. The cylindrical nacelle, which houses the gearbox, generator, and associated equipment, is of length L = 6 m and diameter D = 3 m. If the turbine produces P = 2.5 MW of electrical power, and the air and surroundings temperatures are T = 25 oC and Tsur = 20 oC, respectively, determine the minimum possible operating temperature inside the nacelle. The emissivity of the nacelle is 0.83, and the convective heat transfer coefficient is h = 35 W/m2 .K. The surface of the nacelle that is adjacent to the blade hub can be considered to be adiabatic, and solar irradiation may be neglected. Use Fin or N number of fins to reduce the Ts of the nacelle less than 143 oCarrow_forward6.13 from A Heat Transfer Textbook fifth editionarrow_forward
- If heated at the same rate and in the same manner, which would have a more even heat distribution during heating, a copper pan or a cast iron one? Why?arrow_forwardIf the container is placed in a colder environment, how will it affect the actual heat transfer and the irreversibility of the system?arrow_forwardConsider mixing some of the ice water with the hot water and vice versa so that the two reservoirs are closer to the same temperature. What do you think will happen to the mechanical/thermodynamic efficiency and ideal Carnot efficiency of the heat engine?arrow_forward
- A power station uses oil-fired boilers which are supplied with fuel from 4 cylindrical tanks, each with 12 m diameter and 11 m high. The calorific value of the oil is 38,039 kJ/kg and its relative density is 0.78. The output from the power station is 77 MW. Assuming the only 21% of the heat input is converted to into electrical energy output, how long will the boilers run (in days) on the oil in the tanks. Correct Answer: 4.7 ± 0.1arrow_forwardA student living in a 4 - m 5 - m 3 - m dormitory room turns on her 100 - W fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the windows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back 8 h later. Use specific heat values at room temperature, and assume the room to be at 100 kPa and 20 ° C in the morning when she leaves.arrow_forwardA student living in a 4-m x 6-m x 6-m dormitory room turns on her 150-W fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and windows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back 10 h later. Use specific heat values at room temperature, and assume the room to be at 100 kPa and 15°C in the morning when she leaves. ANS. 58.2 Carrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY