## BecomeMyFan=D 4 years ago An engine burns 1.4 kg of gasoline per hour and yields 3.5 kW of power. Calculate the efficiency of the engine when the heating value of gasoline is 43 MJ/kg.

1. BecomeMyFan=D

i dont even know where to start

2. BecomeMyFan=D

ANY help, even a formula or a rule or a hint, anything will help

3. BecomeMyFan=D

i just know efficiency = input/output

4. lokisan

Yep, calm down.,,

5. BecomeMyFan=D

oh, sorry, it is output/input

6. BecomeMyFan=D

ok,.... i am calm

7. lokisan

The heating value is the amount of heat energy produced by complete combustion in a given quantity. Take a basis of 1 hour. Then your engine burns 1.4kg of gasoline, which yields a maximal amount of thermal energy to use for work as$43MJ/kg \times 1.4 kg=60.2MJ$In one hour, your engine produces from this energy, $\frac{3500J}{s}\times \frac{3600s}{h}=12.6MJ$The efficiency is the amount of work per unit energy input, which is $\eta = \frac{12.6MJ}{60.2MJ}=0.209$to 3 significant figures.

8. lokisan

This is the first time I've used 'heating value' for anything like this, so if the answer's wrong, I couldn't find an appropriate definition.

9. BecomeMyFan=D

so, can i say that efficiancy is 20.9%?

10. lokisan

Yes

11. BecomeMyFan=D

ok, thank you, i already faned you long time ago, so cant fan again :(

12. lokisan

Yeah I know - no worries :)

13. lokisan

The answer makes sense - I've seen values between 10 and 50% for internal combustion engines.

14. BecomeMyFan=D

then it is probably correct, i also know that cobustion engines are very unefficient

15. BecomeMyFan=D

hey anwar

16. AnwarA

hi :)

17. BecomeMyFan=D

want a fan?

18. AnwarA

would you be one if I say yes?

19. BecomeMyFan=D

...

20. AnwarA

lol

21. BecomeMyFan=D

you got it

22. AnwarA

thanks!!

23. BecomeMyFan=D

anwar, can you please fan lokisan, because he helped me alot and i can only fan him once

24. AnwarA

25. AnwarA

so you faned me just as an exchange for me to fan the guy huh? :(

26. BecomeMyFan=D

nah, would have faned you anyway

27. sstarica

lol andy, you and your fanning job~ ^_^