**8. Conclusions**

Nowadays, heat exchangers play a vital role in the operational efficiency and effectiveness at every processing facility in which heat is essential, whether it is an oil refinery, combined heat and power plants, solar and biomass power plant, etc. As energy efficiency importance grows, the role of heat exchangers will become even greater and their technologies more advanced. Fouling on heat transfer surfaces of power plants are a major economic and environmental problem worldwide. Estimates have been made of fouling costs due primarily to wasted energy through excess fuel burn that are as high as 0.25% of the gross national product (GNP) of the industrialized countries. Many millions of tons of carbon emissions are the result of antifouling inefficiency.

After this study of the state of the art of fouling in heat exchanger, the main conclusion is that fouling problem is latent and unresolved. For this reason, new research projects must be developed to investigate and resolve this old problem without environmental effect.
