PRESSURE COMPENSATED FLOW RATE CONTROLLER WITH BTU METER

Apparatus, systems, and methods related to a constant-flow control valve and BTU meter assembly that has a pressure independent, constant-flow control valve assembly connectable to the fluid-based heating or cooling system. A valve stem is connected to a valve member and is rotatable as a unit relative to a valve body to change the position of valve member to change a fluid flow rate through the valve. The valve member's position relative to the fluid path is directly related to the fluid flow rate. Pressure sensors measure the pressure of fluid entering and exiting the valve body. A BTU meter assembly is connected to the valve stem, which is rotatable relative to the BTU meter assembly. A position sensor of the BTU meter assembly detects a rotational position of the valve stem relative to the BTU body. A controller of the BTU meter assembly is coupleable to the position sensor, the pressure sensors, and the temperature sensors, and the controller determines the fluid flow rate based upon the pressure drop across the valve assembly and the rotational position of the valve stem. The controller also determines energy usage of the heating or cooling device based upon the flow rate and the temperature change across the heating or cooling device.