Energy Audit Building Systems an Engineering Approach 2nd. Edition by Krarti, Moncef | 9781439828717 | 1439828717 | Holooly

Energy Audit Building Systems an Engineering Approach [EXP-65108]

60 SOLVED PROBLEMS

Question: 15.3

(a) Estimate the annual energy cost of domestic hot water heating for an office building occupied by 1,000 people. Each person uses on average 3 gallons per day of hot water. The water temperature at the bathroom sink is 120°F. Due to the length of the distribution system, an average of 20°F

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(a) Using Eq. (15.1), the annual fuel use by the w...

Question: 7.2

A 50,000-cfm CV air-handling unit is to be converted to a VAV system. The motor for the existing supply fan is rated at 35 hp with 90 percent efficiency. The fan is operated for 3,500 hours/year according to the following load profile:

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The electrical energy input of the supply fan moto...

Question: 6.1

A blower door test has been performed in a house located in Evergreen, Colorado. The results of the pressurization and depressurization tests are summarized in Figure 6.4 based on the results of the blower door. Determine the leakage areas and ACHs for both pressurization and depressurization tests.

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To determine the air leakage characteristics of a ...

Question: 3.1

A building owner has $10,000 available and has the option to invest this money in either (i) a bank that has an annual interest rate of 7 percent or (ii) buying a new boiler for the building. If he decides to invest all the money in the bank, how much will the building owner have after ten years? Compare

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If the interest is compounded, using Eq. (3.6) wit...

Question: 10.3

A centrifugal chiller (having a capacity of 500 kW and an average seasonal COP of 4.0) operates with a leaving chilled water temperature of 4.5°C. Determine the cost savings incurred by installing an automatic controller that allows the leaving chilled water temperature to be set

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Using Figure 9.13 (refer to Chapter 9), the increa...

Question: 11.3

A compressed air system has a mechanical power requirement of 100 kW with a motor efficiency of 87 percent. The intake air for the compressor is from the interior of the mechanical room (where the compressor is located and where the average annual temperature is 35°C).

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Using Eq. (11.8), the electrical energy savings du...

Question: 11.4

A compressed air system has a mechanical power requirement of 50 kW with a motor efficiency of 90 percent. Determine the cost savings of reducing the discharge absolute pressure from 800 kPa to 700 kPa. Assume that: • The compressor is operating 4,000 hours per year with an average load factor of 70 percent.

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Assuming that the intake air pressure of the compr...

Question: 8.1

A flue gas analysis of an oil fuel-fired boiler indicates that the CO2 content is 11 percent with a gas flue temperature of 343°C (650°F). Determine the overall thermal efficiency of the boiler. Use oil No. 2.

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By reading the monograph of Figure 8.4, the combus...

Question: 10.1

A hot water heating coil has a set-point of 35°C with a throttling range of 10oC. The heat output of the coil varies from 0 to 50 kW. Assuming that a proportional controller is used to maintain the air temperature set-point, determine the proportional gain for the controller and

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Using Eq. (10.1), the relationship between the hea...

Question: 11.5

A leak of 5 mm has been detected in the compressed air distribution lines. Determine the payback period for repairing the leak. Assume an isothermal compression. Use the following information: • The total cost of the leak repair is $150.

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Using Eq. (11.7), the waste in the compressed mass...

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