Concept explainers
The fraction of cost due to heat loss and the time taken for the insulation to pay itself.
Explanation of Solution
Given:
Height of the heater is 2 m.
Diameter of the heater is 40 cm.
Temperature of hot water is
Temperature of the room is
The heater transfer coefficient on the inner surface of the heater is
The heater transfer coefficient on the outer surface of the heater is
Diameter of the sheet metal tank is 46 cm.
Thermal conductivity of foam is
Unit cost is
Annual cost is
Thickness of insulation is 3cm.
Thermal conductivity of fiberglass is
Calculation:
The total thermal resistance is,
The rate of heat transfer is,
The heat lost per year is,
The cost due to energy lost is,
Calculate the fraction of cost due to heat loss.
Thus, the fraction of cost due to heat loss is
The total thermal resistance when insulation is added is,
The heat transfer rate when insulation is added is,
The savings in energy is,
Calculate the time required for the insulation to pay itself.
Thus, the time required for the insulation to pay itself is
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Chapter 17 Solutions
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