LO 11-9 Explain the application of heavy-duty on-board diagnostics and the use of electrical actuators and electronic controls in hybridized diesel engine cooling systems

1.2. Rankine Cycle Waste Heat Recovery Systems

Rankine Cycle Waste Heat Recovery Systems

Repurposing normally wasted exhaust and coolant heat to drive electrically or hydraulically operated devices is another example of a hybridized cooling system. Alternators and accessory drive components can literally be driven by steam power Figure 75. These devices operate on the principle of the Rankine cycle, where an intermediate heat exchanger is added to a loop in the hot cooling system. The heat exchanger contains a fluid with low boiling temperatures. The vapor pressure of this liquid, when heated and boiled in an expander, can be used like steam to drive mechanical devices. Wasted heat from the exhaust or cooling system is sent to a Rankine cycle expander where the liquid is evaporated. Following its use, a condenser converts the Rankine cycle vapor back into a liquid to start the cycle over again Figure 76.

FIGURE 11-75: A Rankine cycle device mounted to the frame rail can extract heat from the exhaust or cooling system to power mechanical accessories, such as alternators, power steering pumps, A/C compressors, or other accessory drive devices.

FIGURE 11-76: A schematic of a Cummins-Rankine waste heat recovery system. Coolant heat is repurposed to drive a device by converting heat energy to power a mechanical drive gear connected to the geartrain.