## BecomeMyFan=D Group Title 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. 3 years ago 3 years ago

1. BecomeMyFan=D Group Title

i dont even know where to start

2. BecomeMyFan=D Group Title

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

3. BecomeMyFan=D Group Title

i just know efficiency = input/output

4. lokisan Group Title

Yep, calm down.,,

5. BecomeMyFan=D Group Title

oh, sorry, it is output/input

6. BecomeMyFan=D Group Title

ok,.... i am calm

7. lokisan Group Title

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 Group Title

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 Group Title

so, can i say that efficiancy is 20.9%?

10. lokisan Group Title

Yes

11. BecomeMyFan=D Group Title

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

12. lokisan Group Title

Yeah I know - no worries :)

13. lokisan Group Title

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

14. BecomeMyFan=D Group Title

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

15. BecomeMyFan=D Group Title

hey anwar

16. AnwarA Group Title

hi :)

17. BecomeMyFan=D Group Title

want a fan?

18. AnwarA Group Title

would you be one if I say yes?

19. BecomeMyFan=D Group Title

...

20. AnwarA Group Title

lol

21. BecomeMyFan=D Group Title

you got it

22. AnwarA Group Title

thanks!!

23. BecomeMyFan=D Group Title

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

24. AnwarA Group Title

25. AnwarA Group Title

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

26. BecomeMyFan=D Group Title

nah, would have faned you anyway

27. sstarica Group Title

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