Another passive mechanism of process intensification is surface modification

Heat transfer intensifications, therefore, are in two categories. The passive category focuses on the external powers of systems while the active category emphasizes rotational effects. Passive techniques incorporate the host equipment enhancement techniques. These techniques include coating surfaces, surface catalysis, and porous structures, among others (Kearney, 1999).

Passive enactments are characterized by the coatings that are applied to surfaces to promote transformations of fluids to liquid or steam. In addition to that, it has been demonstrated that dropwise condensation of fluids comes with positive benefits overall. It sustains endothermic processes within these systems and leads to optimum heat intensifications. In addition to that, coating surfaces also intensify the heat and mass transfer and make them act as catalysts.

By integrating these techniques into the process, heat and mass transfer are intensified. Despite these advantages, catalytic surfaces suffer from the disadvantage of a short lifespan. Another passive mechanism of process intensification is surface modification. Surfaces can either be fully or partially penetrated in the welding and drilling process. These processes allow the formation of protruding features that impact heat transfer in the process. This approach optimizes heat transfer on surfaces by using protruding microns that form on the surface of the material.

Extended surfaces intensify heat transfer by making use of the passive heat transfer technique. Extended surfaces include motor vehicle rotors and radiator fans. Other examples are rotary absorption heat pumps. Heat transfer can be intensified in this process by designing and redesigning the surface that comes into contact with the fluid or mass in the transfer process.