Film and Dropwise Condensation

Product Description

Description of Film and Dropwise Condensation:

Vapour may condense onto a cooled surface in two distinct modes known as Filmwise and Dropwise. For the same temperature difference between the vapour and the surface, Dropwise Condensation is several more times effective than filmwise. However it involves special surface finishes or treatment in order to maintain Dropwise Condensation and for this reason, though desirable, it seldom occurs in real plant operation.

The process of Dropwise Condensation is enhanced by the special water cooled condenser surface finish that prevents wetting of the surface. Condensation then occurs in droplets which grow and fall under gravity. These falling droplets wipe the surface clean ready for more droplets to form. This continuous cleaning puts the water cooled surface in direct contact with the vapour.

The duplicate Filmwise Condenser is not specially treated and allows condensation to form as a film. This effectively grows and runs down the condenser gaining thickness as it falls. The film effectively acts as a resistance to heat transfer, as heat must be conducted through this film to the internal cooling water.

Experimental Capability of Film and Dropwise Condensation:

• Visual observation of Filmwise And Dropwise Condensation and .nucleate boiling.
• Measurement of heat flux and surface heat transfer coefficient in both Filmwise And Dropwise Condensation at pressures up to atmospheric.
• Investigation of the saturation pressure/temperature relationship for water between ambient temperature (20-30°C) and 100°C.
• Demonstration and investigation of the effect of air in condensers.
• Demonstration of Daltons law.

Specification of Film and Dropwise Condensation:

The process of Dropwise Condensation is enhanced by the special water cooled condenser surface finish that prevents wetting of the surface. Condensation then occurs in droplets which grow and fall under gravity. These falling droplets wipe the surface clean ready for more droplets to form. This continuous cleaning puts the water cooled surface in direct contact with the vapour. The duplicate filmwise condenser is not specially treated and allows condensation to form as a film. This effectively grows and runs down the condenser gaining thickness as it falls. The film effectively acts as a resistance to heat transfer, as heat must be conducted through this film to the internal cooling water. Thermocouples are fitted to the surfaces of both condensers allowing the direct comparison of surface temperatures in both Filmwise And Dropwise Condensation.