Abstract

Condensation is one of the most effective ways of transferring heat and it is widely used in power generation units, refrigeration and air-conditioning system, water desalination systems, petroleum industry, chemical production plant, electronics thermal management, etc. Condensation heat transfer depends on many factors including surface material, surface morphology, degree of sub-cooling, characteristics of the fluid used, presence of impurities, etc. Among different properties, surface modification is an easy and effective way to enhance the condensation heat transfer behavior. Condensation behavior on coated, hydrophilic, hydrophobic, sine shaped groove, etc. has already been researched comprehensively but the effect of wedge shaped groove (mimic to leaf vein structure) on copper plate is yet to be explored. Surfaces of some plants and animals have natural ability to harvest water from the environment in an effective and efficient way. In this research, it is tried to mimic the leaf vein structure (wedge shaped groove) on copper plate and then carried out condensation heat transfer experiment. Due to fabrication of wedge shaped groove on copper plate, contact angle and droplet parameters like droplet size, droplet frequency, droplet growth rate, droplet coalescence rate, droplet drainage rate, etc. are affected. Condensation heat transfer behavior like condensation heat transfer co-efficient, contact angle, droplet diameter, droplet growth rate, droplet frequency, sliding velocity of condensate, etc. have been studied for both flat and wedge shaped micro grooved copper plate in this article. Due to the fabrication of leaf vein structure on copper plate it is observed that contact angle has increased significantly and active nucleation site of droplets has decreased which enhanced dropwise condensation. Falling droplet diameter and surface rejuvenation time has increased for modified copper plate. This larger diameter droplets slided faster in wedge shaped copper plate compared to flat copper plate due to gravity. But the condensate drainage rate is less for modified copper plate due to the increment of falling droplet diameter and surface rejuvenation time. A comparative study of droplet parameters and condensation heat transfer parameters have also been shown in this article. It is observed from the droplet nucleation process, coalescence rate and droplet drainage process that dropwise condensation is more stable in case of wedge shaped groove copper plate compared to flat copper plate thus the surface modification is effective in condensation process of copper plate like nature. Results obtained from this condensation heat transfer experiment shows that heat transfer co-efficient of wedge shaped groove copper plate is 20–50% greater compared to flat copper plate. Plausible reason of this enhancement has been broadly discussed in this paper.

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