In a cyclical process, such as a heat engine, the net work done by the system equals the net heat transfer into the system, or \(W=Q_{\mathrm{h}}-Q_{\mathrm{c}}\), where \(Q_{\mathrm{h}}\) is the heat...In a cyclical process, such as a heat engine, the net work done by the system equals the net heat transfer into the system, or \(W=Q_{\mathrm{h}}-Q_{\mathrm{c}}\), where \(Q_{\mathrm{h}}\) is the heat transfer from the hot object (hot reservoir), and \(Q_{c}\) is the heat transfer into the cold object (cold reservoir).
Figure \(\PageIndex{3}\): (a) Heat transfer from a hot object to a cold one is an irreversible process that produces an overall increase in entropy. (b) The same final state and, thus, the same change...Figure \(\PageIndex{3}\): (a) Heat transfer from a hot object to a cold one is an irreversible process that produces an overall increase in entropy. (b) The same final state and, thus, the same change in entropy is achieved for the objects if reversible heat transfer processes occur between the two objects whose temperatures are the same as the temperatures of the corresponding objects in the irreversible process.
Just as discussed for the Otto cycle in the previous section, this means that efficiency is greatest for the highest possible temperature of the hot reservoir and lowest possible temperature of the co...Just as discussed for the Otto cycle in the previous section, this means that efficiency is greatest for the highest possible temperature of the hot reservoir and lowest possible temperature of the cold reservoir. (This setup increases the area inside the closed loop on the \(PV\) diagram; also, it seems reasonable that the greater the temperature difference, the easier it is to divert the heat transfer to work.) The actual reservoir temperatures of a heat engine are usually related to the type…
