EGEE5 - Appliances Household appliances, cooking, and...

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Appliances Household appliances, cooking, and lighting consume 33% of energy at home o Waterheating is the second largest energy expense after home heating and cooling 14% of utility bill Appliance Standards Program set by the US department of Energy o All major home appliances must meet this o Must use standard test procedures to prove the energy use and efficiency of their products o Test results are printed on yellow Energy Guide labels which manufacturers are required to display on appliances Must put labels on refrigerators, freezers, dishwashers, clothes washer, water heaters, furnaces, boilers, central airconditioners, room air conditioners, heat pumps, and pool heaters Label must specify: model, energy efficiency rating and the estimated annual energy consumption of the model, and the range of estimated annual energy consumption or energy efficiency ratings of comparable appliances Water heaters o Heat is continuously flowing from the tank of the water heater and the pipes to the room because the water heater is always at a higher temperature than the surroundings o Thermal energy flows from high temperature to low temperature Heat is lost whether you use water or not o Average life expectancy of 13 years Therefore initial purchase price should not be an important factor o Two Costs associated with water heaters:
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Initial purchase price Energy-efficient model has a higher price but in the end you spend less money each month and get the same amount of hot water so it end up being the better purchase Operating costs An energy-efficient model could save hundreds of dollars in the long run in the energy costs and may offset the higher initial purchase price Energy costs increase with water temperature o Dishwashers require the hottest water of all household uses, 135-140 degrees F Usually come with booster heaters o Heat required to heat water: Q=m x C p x ΔT Where: m= mass of water heated (needs to be converted to pounds) C p is the heat capacity of water (1 BTU/lb degree F) ΔT= temperature difference Example: It is estimated by the United States Department of Energy that a family of four each showering for 10 minutes a day consumes about 700 gal of hot water a week. Water for the showers comes into the home at 55ºF and needs to be heated to 120ºF. o m= mass of water heated= 700 gallons= 5810 lbs o C p = heat capacity of water= 1 BTU/lb degree F o ΔT= temperature difference=120 degree F-55 degree F= 65 degree
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Heat Required= 5810 lbsx1BTU/lbFx65F=377,650 BTU/week Estimate the % energy savings of an electric water heater that heats 100 gallons of per day 
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EGEE5 - Appliances Household appliances, cooking, and...

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