Flow control devices and methods for a once-through horizontal evaporator

A method comprising:

• discharging a working fluid through a once-through evaporator;
• where the once-through evaporator comprises:
• an inlet manifold;
• a plurality of inlet headers in fluid communication with the inlet manifold;
• a plurality of tube stacks, where each tube stack comprises one or more substantially horizontal evaporator tubes;
• each of the tube stacks being in fluid communication with one of the plurality of inlet headers;
• a plurality of outlet headers, each outlet header being in fluid communication with one of the tube stacks;
• an outlet manifold in fluid communication with each of the plurality of the one or outlet headers;
• each of the plurality of tube stacks aligned one above another in a direction perpendicular to a length of the evaporator tubes;
• a plurality of flow control devices to dynamically control the flow of a working fluid to a respective inlet header;
• a plurality of pressure sensors, each pressure sensor coupled to one of the tube stacks near a center thereof, each pressure sensor in fluid communication with a working fluid carried within the tube stack;
• a plurality of temperature sensors, one of the temperature sensors located in each of the outlet headers for monitoring the temperature of a working fluid within the outlet header;
• a controller in operative communication with the flow control devices, the pressure sensors and the temperature sensors, the controller being configured to achieve a balanced pressure drop in a working fluid to balance flow distribution between the plurality of tube stacks;
• discharging a hot gas from a furnace or boiler through the once-through evaporator;
• where a direction of flow of hot gas is perpendicular to a direction of flow of the working fluid;
• and
• measuring a parameter of the working fluid with at least one of the temperature and pressure sensors;
• changing a rate of discharge of the working fluid through the once-through evaporator if the parameter lies outside a desired value;
• where the change in the rate of discharge is brought about by one of the flow control devices;
• and
• controlling the flow control devices to achieve a balanced pressure drop in the working fluid to balance flow distribution between the plurality of tube stacks.

A once-through horizontal evaporator for carrying a working fluid comprising:

• a horizontal duct to pass a flow of heated gas;
• an inlet manifold;
• a plurality of inlet headers in fluid communication with the inlet manifold;
• a plurality of tube stacks, where each tube stack comprises one or more substantially horizontal evaporator tubes, each of the tube stacks being vertically stacked one on top of another within the horizontal duct;
• each of the tube stacks being in fluid communication with one of the plurality of inlet headers;
• a plurality of outlet headers, each outlet header being in fluid communication with one of the tube stacks;
• an outlet manifold in fluid communication with each of the plurality of outlet headers;
• each of the plurality of tube stacks aligned one above another in a direction perpendicular to a length of the evaporator tubes;
• a plurality of flow control devices to dynamically control the flow of a working fluid to a respective inlet header;
• a plurality of pressure sensors, each pressure sensor coupled to one of the tube stacks near a center thereof, each pressure sensor in fluid communication with a working fluid carried within the tube stack;
• a plurality of temperature sensors, one of the temperature sensors located in each of the outlet headers for monitoring the temperature of a working fluid within the outlet header;
• a controller in operative communication with the flow control devices, the pressure sensors and the temperature sensors, the controller being configured to achieve a balanced pressure drop in a working fluid to balance flow distribution between the plurality of tube stacks.