Rankine Power System With Working Fluid Tank And Control System

A power pack for converting waste heat from exhaust gases of an internal combustion engine to electrical energy, the power pack comprising:

• a working fluid loop fluidly connecting an evaporator, an expander, a condenser and a pump, the working fluid loop containing a volume of working fluid, wherein the evaporator is operable to place the working fluid in thermal communication with the exhaust gases of the internal combustion engine and the condenser is operable to place the working fluid in thermal communication with a coolant flowing through the condenser;
• a working fluid tank, the working fluid tank fluidly connected to the working fluid loop between an outlet of the condenser and an inlet of the pump, the working fluid tank having a single working fluid port, the working fluid port operable to receive working fluid from the outlet of the condenser and to supply working fluid to the inlet of the pump;
• and
• a power pack control unit in communication with the working fluid tank, the power pack control unit operable to change a pressure of the working fluid in the working fluid loop at the inlet of the pump by changing the pressure of the working fluid in the working fluid tank based on a temperature of the coolant at a coolant inlet of the condenser.

A method of maintaining a minimum desirable pressure in a working fluid tank of a waste heat recovery power pack, the method comprising:

• operating a pump to circulate a working fluid through a working fluid loop fluidly connecting the working fluid tank, the pump, an evaporator, an expander and a condenser;
• receiving a signal indicative of a temperature of a coolant at a coolant inlet of the condenser of the waste heat recovery power pack, wherein the condenser places the coolant in thermal communication with the working fluid;
• comparing a pressure in the working fluid tank to a minimum desirable tank pressure, wherein the minimum desirable tank pressure is based on the temperature of the coolant at the coolant inlet;
• and
• adjusting the pressure in the tank to the minimum desirable tank pressure if the pressure in the working fluid tank is different from the minimum desirable tank pressure.