Engineering Fundamentals (Looseleaf)
5th Edition
ISBN: 9781337703574
Author: MOAVENI
Publisher: Cengage
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Chapter 13, Problem 12P
To determine
Find the electrical energy consumed by the unit in 1hour and cost to run air-conditioning unit for a month (31 days) and its coefficient of performance (COP).
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The Energy Efficiency Rating (EER) of an air-conditioning unit is defined asthe ratio of the heat removed in Btu/h divided by the energy used in watts.The EEI (Edison Electric Institute) names an air-conditioning unit as anEnergy Star unit if it has an EER of 13 or greater. A 21⁄2-ton air-conditioningunit uses 2.41 kilowatts (2,410 watts) of energy. One ton is equivalent to12,000 Btu/h. Can this unit be termed an Energy Star unit?
Replacing incandescent lights with energy-efficient fluorescent lights can reduce the lighting energy consumption to one-fourth of what it was before. The energy consumed by the lamps is eventually converted to heat, and thus switching to energy-efficient lighting also reduces the cooling load in summer but increases the heating load in winter. Consider a building that is heated by a natural gas furnace with an efficiency of 80 percent and cooled by an air conditioner with a COP of 3.5. If electricity costs $0.12/kWh and natural gas costs $1.40/therm (1 therm = 105,500 kJ), determine if efficient lighting will increase or decrease the total energy cost of the building (a) in summer and (b) in winter.
An inventor claims to have developed a refrigerator that at steady state requires a net power input of 1.1 horsepower to remove
12,000 Btu/h of energy by heat transfer from the freezer compartment at 20°F and discharge energy by heat transfer to a kitchen at
70°F.
Evaluate this claim.
The inventor's claim is
Chapter 13 Solutions
Engineering Fundamentals (Looseleaf)
Ch. 13.2 - Prob. 1BYGCh. 13.2 - Prob. 2BYGCh. 13.2 - Prob. 3BYGCh. 13.2 - Prob. 4BYGCh. 13.2 - Prob. 5BYGCh. 13.2 - Prob. BYGVCh. 13.4 - Prob. 1BYGCh. 13.4 - Prob. 2BYGCh. 13.4 - Prob. 3BYGCh. 13.4 - Prob. 4BYG
Ch. 13.4 - Prob. BYGVCh. 13.5 - Prob. 1BYGCh. 13.5 - Prob. 2BYGCh. 13.5 - Prob. 3BYGCh. 13.5 - Prob. 4BYGCh. 13.5 - Prob. 5BYGCh. 13.5 - Prob. BYGVCh. 13 - Prob. 1PCh. 13 - Prob. 2PCh. 13 - An elevator has a rated capacity of 2200 lb. It...Ch. 13 - Prob. 4PCh. 13 - Prob. 5PCh. 13 - Prob. 6PCh. 13 - Prob. 7PCh. 13 - Prob. 8PCh. 13 - Prob. 9PCh. 13 - Prob. 10PCh. 13 - Prob. 12PCh. 13 - Prob. 14PCh. 13 - Prob. 15PCh. 13 - Prob. 16PCh. 13 - Prob. 17PCh. 13 - Prob. 18PCh. 13 - Prob. 19PCh. 13 - Prob. 20PCh. 13 - Prob. 22PCh. 13 - Prob. 23PCh. 13 - Prob. 24PCh. 13 - Prob. 25PCh. 13 - Prob. 26P
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- The Energy Efficiency Rating (EER) of an air-conditioning unit is defined asthe ratio of the heat removed in Btu/hr divided by the energy used in watts. Awindow air conditioner is rated at 5,170 Btu. It uses 470 watts of power. Whatis this unit’s EER?arrow_forward1) Heating the water in a 55-gallon water heater requires about 2.0 x 103 kJ of energy. a) Assume the energy came from natural gas with 80% efficiency; how many grams of natural gas are required? b) Assume the energy came from electricity with 80% efficiency and that the electricity was produced from the combustion of coal with 30% efficiency; how many grams of coal are required? For problem above, calculate how much CO2 in grams is emitted to the atmosphere. For a: Use the balanced equation for the combustion of methane (CH4) to determine how many grams of CO2are produced from the amount of natural gas required. For b: Assume that coal produces 5.25 kJ of energy per gram of CO2 produced. Calculate how much CO2 in grams is produced.arrow_forwardPlease help solve both for homework.arrow_forward
- For a building located in London, England with annual heating degree-days (dd) of 5634, a heating load (heat loss) of 42,000 kj/h, and a design temperature difference of 35° C (20° C indoor), estimate the annual energy consumption. If the building is heated with a furnace with an efficiency of 98%, how much gas is burned to keep the home at 20° C? State yourassumptions.arrow_forwardThe design fluid (typically water and antifreeze) flow rate through a solar hot-water heater system is (1 L/s) m ⁄m2 . If a system runs continuously for 3 hours and makes use of two solar panels (each 2 m×4 m) , what is the total volume of the fluid that goes through the collector during this period? Express your answer in liters and m3 .arrow_forwardA heat pump supplies heat energy to a house at the rate of 140,000 kJ/h when the house is maintained at 25°C. Over a period of one month, the heat pump operates for 100 hours to transfer energy from a heat source outside the house to inside the house. Consider a heat pump receiving heat from two different outside energy sources. In one application the heat pump receives heat from the outside air at 0°C. In a second application the heat pump receives heat from a lake having a water temperature of 10°C. If electricity costs $0.105/kWh, determine the maximum money saved by using the lake water rather than the outside air as the outside energy source.arrow_forward
- 4. The human heart pumps the average adult's 6.0 liters (6000 cm3) of blood through the body every minute. The heart must do work to overcome frictional forces that resist blood flow. The average blood pressure is 1.3x104 N/m² a) How much work does the heart do to move the 6.0 liters of blood completely through the body? b) What power output must the have to do this task once a minute? Hint: When the heart contracts, it applies a force to the blood. Pressure is force/area. Model the circulatory system as a single closed tube, with crosssectional area A and volume V=6.0 liters, filled with blood to which the heart applies a force.arrow_forwardpls answer completelyarrow_forwardTake a 4,000 G.S.F. home from 8290 CFH to 1409 CFH in a climate with 4246 HDD. What are the savings? Give your answer in Btus of heating energyarrow_forward
- If a water treatment plant uses 124 chlorine cylinders (cy) during a 30-day period, the average supply from each cylinder is 135 lb. What is the total weight (in lb) of chlorine used in 30 days?arrow_forwardWater falls from a height of 500 m and the mass of water is 50 kg. What is approximately the rise in temperature of water at the bottom if the whole energy is used to heat the water? Specific heat of water is 4.18 kJ/kg-deg C. O 5000 deg C O 1173 deg C O 500 deg C O 0.23 deg C O none of the abovearrow_forwardA house has a volume of 1200 m3 (a) What is the total massof air inside the house at 15°C? (b) If the temperature dropsto –15°C what mass of air enters or leaves the house?arrow_forward
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