A furnace supplies 28kW of thermal power at 300C to an engine and exhausts waste energy at 20C. At the very best, how much work could we expect to get out of the system per second

The amount of work we could expect to get out of the system per second = 28,000J/s

Explanation:

Given the power supplied to the system as  28kW;

Energy = power / time

At very best, the amount of work we could expect to get out of the system per second = 28,000 W / 1 second =  28,000J/s

Therefore, for a a furnace which supplies 28kW of thermal power at 300C to an engine and exhausts waste energy at 20C.

At the very best, the amount of work we could expect to get out of the system per second = 28,000J/s