Waste heat recovery system and method of operating the same

A method of operating a Rankine cycle, comprising:

• operating a pump to circulate a flow of working fluid through a fluid circuit of the system, wherein the flow working fluid is delivered to the pump as a low-pressure liquid and exits the pump as a high-pressure liquid, the flow of working fluid comprising a first and a second portion;
• passing the flow of working fluid through a first heat exchange section arranged along the fluid circuit;
• passing a hot gas stream through the first heat exchange section to transfer heat from the hot gas stream to the flow of working fluid within the first heat exchange section;
• passing the first portion of the flow of working fluid through a second heat exchange section arranged along the fluid circuit after having passed the flow of working fluid through the first heat exchange section;
• passing the hot gas stream through the second heat exchange section prior to passing the hot gas stream through the first heat exchange section, to transfer heat from the hot gas stream to the first portion of the flow of working fluid within the second heat exchange section;
• non-adiabatically expanding the first portion in an expander arranged along the fluid circuit to recover work therefrom;
• and
• passing the second portion along a branch of the fluid circuit in order to bypass both the second heat exchange section and the expander.

A method of cooling a recirculated exhaust gas flow for an engine, comprising:

• receiving the recirculated exhaust gas flow from the engine into a first heat exchange section;
• transferring heat within the first heat exchange section from the recirculated exhaust gas flow to a first flow of working fluid in order to convert the first flow of working fluid from a liquid state to a superheated vapor state;
• receiving the recirculated exhaust gas flow from the first heat exchange section into a second heat exchange section;
• transferring heat within the second heat exchange section from the recirculated exhaust gas flow to a second flow of working fluid, the second flow of working fluid comprising the first flow of working fluid, wherein a flow rate of the second flow of working fluid is greater than a flow rate of the first flow of working fluid;
• returning the cooled recirculated exhaust gas flow to the engine,
• measuring a temperature of the recirculated exhaust gas flow between the second heat exchange section and the engine via at least one temperature sensor;
• and
• modulating the flow rate of the second flow of working fluid in response to the measured temperature via operating a pump.