what are the common causes of fouling in heat exchanger?How does fouling affect it and pressure drop?
yeap as above,.... thats why every few years a heat exchanger, shell and tube or plate, should be opened and manually cleaned, large automated system will even have a cleaning cycle.
In heat exchangers, there is a 'medium' to exchange the heat and transfer it out.....this medium is generally water. Water contains several minerals in it...(if you were to boil water in a very clean pot, until ALL the water is evaporated(gone), you will observe a residue which is the minerals that did not fly off with the vapor. In a confined situation, even though the water is flowing, mineral and silt will deposit unto the exhangers tubings. This eventually restrict the flow of water(increase the pressure drop), but the worst effect is that is reduces the ability to transfer heat. The resistance to transfer heat across the tubing material and the mineral deposits or 'scale' increases, thereby reducing the efficiency of the exchanger. In a closed loop heat exchanger the medium(water) is constantly treated with chemical additives to prevent scaling and bio-degredation.
