Abstract

Analysis of condensation of vapor on metal surfaces has been in the center of enormous attention due to its omnipotent application in numerous industrial processes. So far condensation on smooth, coated, hydrophobic, hydrophilic, grooved surfaces has been researched comprehensively but the effect of porous surface specially the combined effect of porosity and micro grooved has not been fully explored. In this study, condensation heat transfer performance is analyzed for vertical porous micro grooved copper surface and the change of performance due to varying numbers of pores on the modified micro grooved surface are compared with micro grooved surface with no pores. During condensation vapor releases latent heat and forms condensate droplets throughout the suitable nucleation sites on the surface. To enhance the condensation heat transfer it is preferred to come up with a modified condensation surface which can effectively hamper the film layer generation on the different regions of the surface as a result paves the way for new nucleation sites to develop. And increased nucleation site brings higher condensation rates. In our study, a unique experimental setup is constructed consisting of a cooling chamber and a vapor chamber separated by the porous micro grooved copper surface. Steam is generated by a mini boiler and fed into the vapor chamber. Porous opening on the test surface provided continuous liquid flow from cooling to condensation chamber in a controlled way. Liquids through the opening breaks the layer developed at very early stages and prolongs the drop wise condensation (DWC) time span and helps effectively to reduce the chance for droplet to stay on the surface and coalescence. Wedge pattern micro grooves are inscribed on the test surface providing the additional aid for the drainage of the droplets. As the number of porous opening changes various droplet parameters like droplet sweeping frequency, droplet diameter are subjected to change over time. It also affected the condensation heat transfer parameters to a great extent. A comparative analysis of condensation heat transfer parameters and droplet parameters due to the change of number of pores compared to no pores are carried out and shown with pictures of test surfaces captured real time during the experiment. Performance of the proposed surface is compared with that of the other surfaces based on the condensation rate and condensation heat transfer coefficient. Experimental results indicate heat transfer performance can be enhanced by 30–35% due to introducing the porous opening on the modified surface. The experiments are conducted under low steam pressure conditions.

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