Consider a 1.5-m-high electric hot-water heater that has a diameter of 40 cm and maintains the hot water at 60 °C. The tank is located in a small room whose average temperature is 27 °C, and the heat transfer coefficients on the inner and outer surfaces of the heater are 50 and 12 W/m2⋅K, respectively. The tank is placed in another 46-cm-diameter sheet metal tank of negligible thickness, and the space between the two tanks is filled with foam insulation (k = 0.03 W/m⋅K). The thermal resistances of the water tank and the outer thin sheet metal shell are very small and can be neglected. The price of electricity is $0.08/kWh, and the homeowner pays $280 a year for water heating. Determine the fraction of the hot-water energy cost (in %) of this household that is due to the heat loss from the tank. Heat transfers through the top and bottom of the tank are negligible. In continuation of Question 2, hot-water tank insulation kits consisting of 3-cm-thick fiberglass insulation (k = 0.035 W/m⋅K) large enough to wrap the entire tank are available in the market for about $30. If such insulation is installed on this water tank by the homeowner himself, how long (in months) will it take for this additional insulation to pay for itself? Round up your answer to the next higher integer.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
icon
Related questions
Question
100%

Question 2

Consider a 1.5-m-high electric hot-water heater that has a diameter of 40 cm and maintains the hot water at 60 °C. The tank is located in a small room whose average temperature is 27 °C, and the heat transfer coefficients on the inner and outer surfaces of the heater are 50 and 12 W/m2⋅K, respectively. The tank is placed in another 46-cm-diameter sheet metal tank of negligible thickness, and the space between the two tanks is filled with foam insulation (k = 0.03 W/m⋅K). The thermal resistances of the water tank and the outer thin sheet metal shell are very small and can be neglected. The price of electricity is $0.08/kWh, and the homeowner pays $280 a year for water heating. Determine the fraction of the hot-water energy cost (in %) of this household that is due to the heat loss from the tank. Heat transfers through the top and bottom of the tank are negligible.

 

 

In continuation of Question 2, hot-water tank insulation kits consisting of 3-cm-thick fiberglass insulation (k = 0.035 W/m⋅K) large enough to wrap the entire tank are available in the market for about $30. If such insulation is installed on this water tank by the homeowner himself, how long (in months) will it take for this additional insulation to pay for itself? Round up your answer to the next higher integer.

3 cm
40 cm
27°C
1.5 m
Tw = 60°C
Foam
insulation
Water
heater
Transcribed Image Text:3 cm 40 cm 27°C 1.5 m Tw = 60°C Foam insulation Water heater
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 4 steps with 4 images

Blurred answer
Similar questions
Recommended textbooks for you
Elements Of Electromagnetics
Elements Of Electromagnetics
Mechanical Engineering
ISBN:
9780190698614
Author:
Sadiku, Matthew N. O.
Publisher:
Oxford University Press
Mechanics of Materials (10th Edition)
Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:
9780134319650
Author:
Russell C. Hibbeler
Publisher:
PEARSON
Thermodynamics: An Engineering Approach
Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:
9781259822674
Author:
Yunus A. Cengel Dr., Michael A. Boles
Publisher:
McGraw-Hill Education
Control Systems Engineering
Control Systems Engineering
Mechanical Engineering
ISBN:
9781118170519
Author:
Norman S. Nise
Publisher:
WILEY
Mechanics of Materials (MindTap Course List)
Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:
9781337093347
Author:
Barry J. Goodno, James M. Gere
Publisher:
Cengage Learning
Engineering Mechanics: Statics
Engineering Mechanics: Statics
Mechanical Engineering
ISBN:
9781118807330
Author:
James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:
WILEY