What is the working principle of the heat exchanger?

The heat exchanger is made of multiple layers of materials with good thermal conductivity. The working principle is similar to that of a water heater. A water heater generates heat when gas is burned. The heat exchanger is a heating medium, not an open flame. There are two pipeline loops inside the heat exchanger. One is the heat source and the other is the heated source. The heat source is like the flame when the water heater is burning, such as hot water or steam. The heated source is like the heated water in the water heater. There is also a regulating valve in front of the heat source inlet of the heat exchanger in the heat source loop. By changing the opening of this valve, the temperature of the heated source can be adjusted.