Systems and methods for controlling the pressure of a working fluid at an inlet of a pressurization device of a heat engine system

A heat engine system, comprising:

• a working fluid circuit configured to flow a working fluid therethrough comprising carbon dioxide in a subcritical state and a supercritical state in different locations of the working fluid circuit, the working fluid circuit comprising:
• a waste heat exchanger configured to be in fluid communication and in thermal communication with a heat source stream, and to transfer thermal energy from the heat source stream to the working fluid;
• an expansion device disposed downstream from and in fluid communication with the waste heat exchanger and configured to convert a pressure drop in the working fluid to mechanical energy;
• a recuperator disposed upstream of and in fluid communication with the waste heat exchanger and disposed downstream from and in fluid communication with the expansion device;
• a main pressurization device disposed upstream of and in fluid communication with the recuperator and configured to pressurize and circulate the working fluid within the working fluid circuit;
• and
• a heat exchanger assembly disposed upstream of and in fluid communication with the main pressurization device and disposed downstream from and in fluid communication with the recuperator, the heat exchanger assembly comprising:
• an inlet manifold in fluid communication with the recuperator;
• an outlet manifold in fluid communication with the main pressurization device;
• a plurality of air-cooled heat exchangers fluidly connected to the inlet manifold and the outlet manifold and arranged in parallel with one another, the plurality of air-cooled heat exchangers configured to transfer thermal energy from the working fluid to a cooling medium including air;
• a plurality of fans configured to direct the cooling medium into contact with the plurality of air-cooled heat exchangers;
• a plurality of drivers, each driver configured to drive a respective fan of the plurality of fans;
• and
• a plurality of driver controllers, each driver controller operatively coupled to a respective driver and configured to modulate a rotational speed of the respective fan;
• and
• a main controller communicatively coupled to the plurality of drive controllers and at least one sensor configured to detect a pressure of the working fluid at an inlet of the main pressurization device, the main controller configured to modulate the rotational speed of one or more of the fans to control the pressure of the working fluid at an inlet of the main pressurization device in response to the detected pressure.

A method for controlling a pressure of a working fluid at an inlet of a main pressurization device of a heat engine system, the method comprising:

• circulating the working fluid in a working fluid circuit of a heat engine system via the main pressurization device;
• transferring thermal energy from a heat source stream to the working fluid in a waste heat exchanger of the working fluid circuit;
• expanding the working fluid in an expansion device in fluid communication with the waste heat exchanger;
• detecting the pressure of the working fluid at the inlet of the main pressurization device of the working fluid circuit via one or more sensors;
• modulating a rotational speed of at least one fan configured to direct a cooling medium in contact with a respective gas-cooled heat exchanger of a plurality of gas-cooled heat exchangers of a heat exchanger assembly of the working fluid circuit, wherein modulating the rotational speed of the at least one fan comprises adjusting a thermodynamic quality or density of the working fluid flowing through the heat exchanger assembly based on the detected pressure;
• and
• feeding the working fluid having the adjusted thermodynamic quality or density to the inlet of the main pressurization device, thereby adjusting and controlling the pressure of the working fluid at the inlet of the main pressurization device.