A thermoelectric generator (TEG) is a solid-state semiconductor device that can convert temperature differences and heat flow into electrical energy. Nowadays, industries with high-temperature production processes tend to experience unavoidable heat loss. Heat exchangers are therefore the most widely used equipment to recover these waste heat. The researcher therefore saw the benefits of bringing TEG devices to be installed in heat exchangers. It is thought that in addition to the heat exchanger being a device that helps the heat transfer of one fluid to another fluid. Can also generate electricity back to use as well. This will be of great benefit in increasing the efficiency of waste heat recovery and reducing production costs. In this research, 36 plates of Bismuth Telluride (Bi2Te3) TEG devices were installed in plate and fin heat exchangers and studied the effect of changes in the inlet flow rate of cold water at 20 °C on the effect of heat exchange and the electrical power produced by TEG. The hot water inlet flow rate was constant at 1 l/min and the temperature was constant at 85 °C. Then mathematical model was created to predict the results of the outlet hot water temperature, outlet cold water temperature, current and voltage produced. The model can predict accurately the least squares value (R2) with values of 0.949, 0.859, 0.707 and 0.749, respectively. In addition, a multiple input, multiple output (MIMO) using model predictive controller (MPC) was designed to control the output current, and temperature can control into the setpoint effectively.