Estimate the fuel savings obtained by resetting the hot deck of a 60,000 cfm dual duct system by 2oF during the winter and 1°F during the summer. The HVAC system is operated 80 hours per week and serves a building in Chicago, Illinois. For the analysis, assume that the cost of fuel is

Question

Estimate the fuel savings obtained by resetting the hot deck of a 60,000 cfm dual duct system by 2oF during the winter and 1°F during the summer. The HVAC system is operated 80 hours per week and serves a building in Chicago, Illinois. 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. It should be noted that for Chicago, the number of weeks is 30 for the heating season (winter) and 21 for the cooling season (summer).

Accepted Answer

The annual fuel savings is estimated based on the energy saved through a change in the temperature difference:[latex] ΔT_{H}[/latex] = 2 °F in the winter and [latex] ΔT_{H}[/latex] = 2 °F in the summer:

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

Therefore,

[latex]ΔFU_{H}=\frac {60,000 cfm*(1.08Btu/cfmhr.°F)*[2°F*(30*80hrs)+1°F*(21*80hrs)]}{(0.80)*(10^{6}Btu/MMBtu)} [/latex]

or

[latex]ΔFU_H = 525MMBtu/yr[/latex]

Thus, the hot deck temperature reset can reduce the fuel cost by $3,150/yr.

Question 7.4: Estimate the fuel savings obtained by resetting the hot deck...

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