I calculating the heat exhausted from an engine.

In summary, a 112 hp car engine operating at 11% efficiency has a cold-temperature reservoir of 85°C and a thermal intake temperature of 445°C. The ratio of its efficiency to its maximum possible efficiency (Carnot efficiency) is 0.22. The power going into moving the car is 83552 watts. To calculate the amount of heat exhausted to the air in 1.0 hour, you can use the given power and efficiency to find the heat going into the cold sink, and then multiply by 1.0 hour to get the required energy. This is because the waste heat from the engine ultimately ends up in the atmosphere through the car radiator.
  • #1
yoyo12121
1
0

Homework Statement


A 112 hp car engine operates at 11% efficiency. Assume the engine's water temperature of 85°C is its cold-temperature (exhaust) reservoir and 445°C is its thermal "intake" temperature (the temperature of the exploding gas-air mixture).
(a) What is the ratio of its efficiency relative to its maximum possible (Carnot) efficiency?
eactual / eCarnot =
(b) Calculate how much power (in watts) goes into moving the car.
(c) Calculate how much heat, in joules and in kcal, is exhausted to the air in 1.0 h

Homework Equations


For a) eideal=1-(TL/TH)
For b) (hp)(W)
For c) I need help

The Attempt at a Solution


I got the answers for a and b.
a).22
b)83552

I have no clue how to do c. I need some guidance.

Thanks!
 
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  • #2
Show your working and units for a) & b).

As for c), do you understand how a car radiator works? The hot engine water is cooled by atmospheric air, thus, waste heat ultimately ends up in the atmosphere.

you are given "W" and the efficiency and that's all you need to find the power going to the cold sink "Qc". If you don't know where to start, draw a diagram and apply conservation of energy.
Then multiply by the appropriate time to get the required energy.
 

FAQ: I calculating the heat exhausted from an engine.

1. How is heat exhausted from an engine calculated?

The amount of heat exhausted from an engine can be calculated using the formula Q = mcΔT, where Q is the heat energy, m is the mass of the exhaust gas, c is the specific heat capacity of the exhaust gas, and ΔT is the change in temperature of the exhaust gas.

2. What factors affect the amount of heat exhausted from an engine?

The amount of heat exhausted from an engine can be affected by various factors such as the type of fuel used, the engine design, the load on the engine, and the engine speed. These factors can impact the temperature and mass of the exhaust gas, which in turn affects the amount of heat exhausted.

3. How does the efficiency of the engine impact the heat exhausted?

The efficiency of an engine refers to how much of the energy from the fuel is converted into useful work. A more efficient engine will produce less waste heat and therefore less heat will be exhausted. On the other hand, a less efficient engine will produce more waste heat and therefore more heat will be exhausted.

4. Can the heat exhausted from an engine be reduced?

Yes, the heat exhausted from an engine can be reduced through various methods such as improving the engine's efficiency, using alternative fuels, and implementing exhaust gas recirculation systems. These measures can help decrease the amount of heat exhausted and improve the overall efficiency of the engine.

5. Why is calculating the heat exhausted from an engine important?

Calculating the heat exhausted from an engine is important for several reasons. It can help engineers and scientists understand the performance and efficiency of an engine, identify areas for improvement, and develop more efficient and environmentally-friendly engines. It can also aid in the design and optimization of exhaust systems and contribute to our overall understanding of energy usage and conservation.

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