BMCT 2123 THERMODYNAMICS ITUTORIAL 05

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FACULTY OF MECHANICAL ENGINEERINGBMCT 2123 THERMODYNAMICS I

TUTORIAL 05

1. A steam power plant receives heat from a furnace at a rate of 280 GJ/hour. Heat losses tothe surrounding air from steam as it passes through the pipes and other components areestimated to be 8 GJ/hour. If the waste heat is transferred to the cooling water at a rate of145 GJ/hour, determine:

a) The net power outputb) The thermal efficiency of this power plant.

2. A household refrigerator with a COP of 1.8 removes heat from refrigerated space at a rateof 90 kJ/min. Determine:

a) The electric power consumed by the refrigeratorb) The rate of heat transfer to the kitchen air.

3. An air conditioner removes heat steadily from a house at a rate of 750 kJ/min whiledrawing electric power at a rate of 6 kW. Determine:

a) The COP of this air conditionerb) The rate of heat discharge to the outside air.

4. Determine the COP of a refrigerator, which removes heat from the food compartment at arate of 8000 kJ/hour for each kW of power it consumes. Also determine the rate of heatrejection to the surrounding air.

5. A heat pump with a COP of 1.8 supplies energy to a house at a rate of 75000 kJ/hour.Determine:

a) The electric power drawn by the heat pumpb) The rate of heat removal from the outside air.

6. A Carnot heat engine operates between a source at 1000 K and a sink at 300 K. If the heatengine is supplied with heat at a rate of 800 kJ/min, determine:

a) The thermal efficiencyb) The power output of this heat engine.

7. A heat engine is operating on Carnot cycle and has a thermal efficiency of 55%. The wasteheat from this engine is rejected to a nearby lake at 15oC at a rate of 800 kJ/min.Determine:

a) The power output of the engineb) The temperature of the source.

UNIVERSITI TEKNIKAL MALAYSIA MELAKAKARUNG BERKUNCI 1200

AYER KEROH75450 MELAKA

BMCT 2123 THERMODYNAMICS ITUTORIAL 05

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8. A Carnot refrigerator operates in a room in which the temperature is 25oC. The refrigeratorconsumes 500 W of power when operating, and has a COP of 4.5. Determine:

a) The rate of heat removal from the refrigerated spaceb) The temperature of the refrigerated space.

9. A Carnot heat pump is used for heating a house and maintaining it at 20oC during thewinter. On a day when the average temperature remains at about 2oC, the house isestimated to lose heat at a steady rate of 82000 kJ/hour. If the heat pump consumes 8 kWof power while operating, determine:

a) How long the heat pump ran on that dayb) The total heating costs, assuming an average price of $0.085/kW.hour for

electricityc) The heating cost for the same day if resistance heating is used instead of heat

pump.

10. A Carnot heat engine receives heat from a reservoir at 900oC at a rate of 800 kJ/min andrejects the waste heat to the ambient air at 27oC. The entire work output of the heatengine is used to drive a refrigerator that removes heat from the refrigerated space at –5oC and transfers it to the same ambient air at 27oC. Determine:

a) The maximum rate of heat removal from the refrigerated spaceb) The total rate of heat rejection to the ambient air.