Mass management system for a supercritical working fluid circuit

A heat engine system, comprising:

• a working fluid circuit having a high pressure side and a low pressure side and being configured to flow a working fluid therethrough, wherein at least a portion of the working fluid circuit contains the working fluid in a supercritical state, and the working fluid comprises carbon dioxide;
• a heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit, configured to be fluidly coupled to and in thermal communication with a heat source, and configured to transfer thermal energy from the heat source to the working fluid within the high pressure side;
• an expander fluidly coupled to the working fluid circuit and disposed between the high pressure side and the low pressure side and configured to convert a pressure drop in the working fluid to mechanical energy;
• a driveshaft coupled to the expander and configured to drive a device with the mechanical energy;
• a system pump fluidly coupled to the working fluid circuit between the low pressure side and the high pressure side of the working fluid circuit and configured to circulate or pressurize the working fluid within the working fluid circuit;
• a recuperator fluidly coupled to the working fluid circuit and operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit;
• a cooler in thermal communication with the working fluid in the low pressure side of the working fluid circuit and configured to remove thermal energy from the working fluid in the low pressure side of the working fluid circuit;
• and
• a mass management system fluidly coupled to the low pressure side of the working fluid circuit and comprising:
• an inventory transfer line fluidly coupled to the low pressure side of the working fluid circuit and configured to transfer the working fluid from and to the working fluid circuit on the low pressure side;
• a mass control tank fluidly coupled to the inventory transfer line and configured to receive, store, and dispense the working fluid;
• a system transfer valve coupled to the inventory transfer line and configured to control the transfer of the working fluid from and to the working fluid circuit;
• a tank transfer valve coupled to the inventory transfer line and configured to control the transfer of the working fluid from and to the mass control tank;
• and
• a transfer pump in fluid communication with the mass control tank and the inventory transfer line and configured to control the pressure of a section of the inventory transfer line disposed between the system and tank transfer valves.