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

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

Sustainable Energy

2nd Edition

ISBN:9781337551663

Author:DUNLAP, Richard A.

Publisher:DUNLAP, Richard A.

Chapter8: Direct Use Of Solar Energy

Section: Chapter Questions

Problem 7P

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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.
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?
Copper tubing 0.500 in. in inside diameter is 11.0 ft long. What is the volume of the refrigerant contained in the tubing
Find the energy required to increase the room temperature of a coffee in a cup to a temperature of 60°C.
A 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.
1) 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.
An air-conditioning unit has a cooling capacity of two tons. If the unit has a rated energy efficiency ratio (EER) of 11, how much electrical energy is consumed by the unit in 1 h? If a power company charges 14 cents per kWh usage, how much would it cost to run the air-conditioning unit for a month (31 days), assuming the unit runs 8 h a day? What is the coefficient of performance (COP) for the given air-conditioning unit?
A tank contains 49 gallons of a solution composed of 85% water and 15% alcohol. A second solution containing half water and half alcohol is added to the tank at the rate of 4 gallons per minutes. At the same time, the tank is being drained at the same rate. Assuming that the solution is stirred constantly, how much alcohol will be in tank after 10minutes?
Question 2 Lauren has worker bullding her house on a hot summer day. She prepares a drink for them by adding a certain amount of ice at 0.0 °C to 1.8 kg of tea, initially at 80°C. How much ice in kilograms does she need to get the iced tea to be at final temperature of 10C? The heat of fusion of ice is 333 kJ/kg, specific heat of ice is 2100 J/kg. "Cand that of tea is 4186 Jkg. C 1.0 kg 15 kg O 12 kg
6.0 g of cream at 13.2 °C are added to an insulated cup containing 150.0 g of coffee at 92.9 °C. Calculate the equilibrium temperature of the coffee. You may assume no heat is lost to the cup or surroundings, and that any physical properties of cream and coffee you need are the same as those of water. Be sure your answer has 3 significant digits.
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.
a) Calculate the partial pressure of oxygen in the air at 100 kPa if nitrogen has a partial pressure of 82 kPa and carbon dioxide and water combined have a partial pressure of 0.77 kPa. b) A container of compressed helium has in it 15.0 L pressurized to about 2250 kPa at 24.5°C. How many moles of helium are in the container? c) i) Determine the volume of oxygen gas required to completely combust 5.5 mol of propane (C3H8) in a barbecue at 101.3 kPa and 28.0°C. ii) What mass of helium would be required to fill a balloon to 6.8 L at 100 kPa and 25°C?