Calorimetric Control Of Downhole Tools

Systems and methods are disclosed for controlling a downhole tool by encoding a tool control signal in a fluid flow and obtaining a temperature response downhole. In an example, a system for controlling a downhole tool includes a signal transmitter, a signal receiver, and a controller. The signal transmitter is uphole of the tool to be controlled (e.g., at surface) and encodes the tool control signal by varying one or more fluid flow parameters of a fluid flow down a well. The signal receiver is positionable in the well in fluid communication with the fluid flow. The signal receiver detects a temperature response in the fluid flow resulting from varying the one or more fluid flow parameters. A controller controls the downhole tool according to the temperature response.