Heat engine, how much power does it use in watts?

[Windseaker]

1.A heat engine is rejecting 200btu/h and 30% efficient, how much power does it use in watts?

2. _QH=w+_QC and power=energy/time (1kwh=3412btu)
and a power diagram: QC= wasted heat, w=work

QH
l
30%l---->W
l
QC

3. 200btu/h(1kwh/3412btu)(1000w/1kw)=58.6watts (30%)=17.6watts
This value just seems too small??

 

[ideasrule]

It is too small, but not by much. You're multiplying 58.6% watts, which is the waste heat produced by the heat engine, by efficiency. You need to multiply total energy output (work+waste heat) by efficiency to get the answer.

 

[Windseaker]

Your saying:

Work=17.6watts +waste heat=58.6watts---=76.2watts total

then 76.2watts (x) eff.=30%----=17.9watts used power??

Is this right??