Please help solve both for homework. Problem 5It is well established that the thermal efficiency of a heat engine increases as the temperature TL at which heatis rejected from the heat engine decreases. In a effort to increase the efficiency of a power plant, somebodysuggests refrigerating the cooling water before it enters the condenser, where heat rejection takes place.Would you be in favor of this idea? Why?Problem 6A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated spaceat -35°C by rejecting waste heat to cooling water that enters the condenser at 19°C at a rate of 0.3 kg/s andleaves at 25°C. The refrigerant enters the condenser at 1.4 MPa and 60°C and leaves at the same pressuresubcooled by 10°C. If the compressor consumes 3.2 kW of power, determine (a) the mass flow rate of therefrigerant, (b) the refrigeration load, (c) the COP, and (d) the minimum power input to the compressor forthe same refrigeration load.

Problem 6 : since no given table:Step 1: draw the schematic diagram and P-H & T-S DiagramStep 2:…

Answered: Problem 5 It is well established that…

Sustainable Energy

2nd Edition

ISBN:9781337551663

Author:DUNLAP, Richard A.

Publisher:DUNLAP, Richard A.

Chapter17: Energy Conservation

Section: Chapter Questions

Problem 1P

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Consider a 400-MW, 32 percent efficient coal-fired power plant that uses cooling water withdrawn from a nearby river (with an upstream flow of 10-m3/s and temperature 20 °C) to take care of waste heat. The heat content of the coal is 8,000 Btu/lb, the carbon content is 60% by mass, and the sulfur content is 2% by mass. How much electricity (in kWh/yr) would the plant produce each year? How many pounds per hour of coal would need to be burned at the plant? Estimate the annual carbon emissions from the plant (in metric tons C/year). If the cooling water is only allowed to rise in temperature by 10 °C, what flow rate (in m3/s) from the stream would be required? What would be the river temperature if all the waste heat was transferred to the river water assuming no heat losses during transfer? Estimate the hourly SO2 emissions (in kg/h) from the plant assuming that all the sulfur is oxidized to SO2 during combustion.
Civil engineering: Energy Please solve the problem clearly , don't use previously solved solutions. I am asking this for a second time. Hope you understand Question: The atmosphere is stable with a lapse rate of -0.2 degree C/100 m. The surfaces air temperature is 15 degree C. A parcel of air is released at the ground with a temperature of 25 degree C. Calculate the maximum mixing height, in m.
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.
By how much could the flow rate of fuel gas of Example 11.2 be reduced if a recuperator were used to preheat the waste gas by recovering the enthalpy released when reducing the exhaust gas temperature from 1350 oF to 650 oF? Determine the preheated waste gas temperature as it enters the afterburner.
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?
A refrigerator absorbs 5 kJ of energy from a cold reservoir and rejects 8 kJ to a hot reservoir. (a) Find the coefficient of performance of the refrigerator. (b) The refrigerator is reversible and is run backward as a heat engine between the same two reservoirs. What is its efficiency?
A vendor takes an ice cream cup out of a freezer, kept at -18 degree-Celcius. Outside, the room temperature is 32 degree-Celcius. After 60seconds, the ice cream has warmed to -8 degrees Celcius. What is the temperature of the ice cream after 300 seconds?
The enthalpy of combustion of benzoic acid (C6 H5 COOH) is commonly used as the standard for calibrating constant-volume bomb calorimeters; its value has been accurately determined to be −3226.7 kJ/mol. When 1.9862 g of benzoic acid are burned in a calorimeter, the temperature rises from 21.84°C to 25.67°C. What is the heat capacity of the bomb? (Assume that the quantity of water surrounding the bomb is exactly 2000 g.)
We have exposed 1 kg of water, 1 kg of brick, and 1 kg of concrete each to a heat source that puts out 100 J every second. Assuming that all of the supplied energy goes to each material and they were all initially at the same temperature, which one of these materials will have a greater temperature rise after 10 s? We can answer this question using Equation as shown . We will first look up the values of the specific heat for water, brick, and concrete, which are cwater = 4180 J⁄kg K, cbrick = 960 J⁄kg K and cconcrete = 880 J⁄kg K . Now applying as shown , Ethermal = mc(Tfinal Tinitial) to each situation, it should be clear that although each material has the same amount of mass and is exposed to the same amount of thermal energy, the concrete will experience a higher temperature rise because it has the lowest heat capacity value among the three given materials.
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.
Choose the correct answer 200 g CO2 approximately takes up ____ L volume in air at 1 atm and 0oC? 4480; 100; C. 200; D. Undetermined Which of the following gases has the greatest contribution to the greenhouse effect on the Earth? A. Water vapor; B. CO2; C. CH4; D. O3 Based on what you have learned, which of the following can contribute(s) greenhouse gases? A. landfills; B. a deep lake with organic rich sediments; C. septic tanks; D. all of the above Which of the following gases is NOT a greenhouse gas? A. methane; B. carbon monoxide; C. hydrofluorocarbons; D. water vapor
A 75 gal. electric hot water heater provides 9000 Watts of power to heat water. If the heater is filled with water at an initial temperature of 50ºF, how long will it take for the water to reach 140ºF? Assume that there are no heat losses.

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