Estimate the fuel savings obtained by using low-leakage dampers for a 40,000 cfm airhandling unit which serves an office building located in Chicago, Illinois. The office is conditioned during the entire heating season to 72°F (even during unoccupied hours). It was found that the existing dampers

Question

Estimate the fuel savings obtained by using low-leakage dampers for a 40,000 cfm airhandling unit which serves an office building located in Chicago, Illinois. The office is conditioned during the entire heating season to 72°F (even during unoccupied hours). It was found that the existing dampers have 15 percent leakage when closed. The outdoor air damper system is scheduled to be closed 3,500 hours during the heating season. For the analysis, assume that the cost of fuel is $6/MMBtu and the boiler efficiency is 80 percent. The average heating season outdoor temperature in Chicago is 34.2°F. The low-leakage dampers have a 1 percent leakage.

Accepted Answer

The annual fuel savings is estimated based on the energy saved due to a reduction in the amount of outdoor air volume to be heated from [latex]T_{out}[/latex]= 34.2 °F to [latex] T_{in}[/latex] = 72°F:

[latex]ΔFU_{H}=\frac {Δ \dot{m}_{a}.c_{p}.(T_{out}-T_{in})}{η_{b}}.N_{h,H}[/latex]

Therefore:

[latex]ΔFU_{H}=\frac {40,000 cfm*(0.15-0.01)*(1.08Btu/cfmhr.°F) (72ºF - 34.2ºF)}{(0.80)*(10^{6}Btu/MMBtu)} *3,500hrs/yr[/latex]

or

[latex]ΔFU_H =1,000 MMBtu/yr[/latex]

In terms of cost savings, the use of low-leakage dampers can reduce fuel costs by $6,000/yr.

Question 7.3: Estimate the fuel savings obtained by using low-leakage damp...

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