Simply put, a shell and tube heat exchanger is used to cool fluids on a large scale, such as in an oil refinery. The device consists of a pressure shell that contains tubes. Fluid is directed around the tubes using baffles.
To function, two fluids of different temperatures are fed into the exchanger. One flows through the tubes and the other flows outside the pressure shell. As the second fluid passes over the tubes the heat of the two liquids are exchanged. Tubes come in one-pass and two-pass forms.