Condition monitoring of heat exchanger tubes may be carried out using eddy current inspection. This is often simulated through computation fluid dynamics (CFD). Infrared photography (see Section 2.10.1) may also be used on the exterior of heat exchanges, to reveal significant temperature variations or hot spots.
Fouling can be a serious problem. Often, cooling waters from rivers, estuaries or a sea is used, and biological debris can enter and build layers. Another problem is scale, which is chemical deposit layers, such as calcium carbonate or magnesium carbonate (see Section 3.2.6). The process being cooled can also deposit scale, such as silica scale in alumina refineries. See Examples, below).