Effect of micro groove on condensation behavior of vertical copper plate

Abstract

Condensation is one of the most effective and efficient methods for transferring large amounts of heat, resulting in its widespread use in power generation, air-conditioning and refrigeration system, water desalination system, electronics thermal management, petroleum industry, chemical plant, and other applications. Condensation heat transfer is an efficient but complex phenomenon influenced by a number of factors including surface material properties, surface morphology, fluid properties, degree of sub-cooling, presence of impurities, and so on. Condensation heat transfer can be controlled or enhanced by controlling these factors and among those, surface modification is an easy and effective technique to enhance condensation heat transfer behavior. Condensation behavior on coated surfaces, hydrophilic surfaces, hydrophobic surfaces, and triangular grooved surfaces, etc. has already been widely studied, but the effect of rectangular, wedge and sinusoidal shaped micro groove on condensation behavior is yet to be investigated. Contact angle and droplet parameters such as droplet size, droplet frequency, droplet growth rate, droplet coalescence rate, droplet drainage rate, and others are affected by introducing various micro grooves on copper surfaces, and all these parameters, as well as heat transfer behavior, have been studied in this experimental study for both flat and micro-grooved vertical copper surfaces. In the case of micro-grooved copper surfaces, droplet density dropped, and droplet coalescence was reduced, indicating that smaller diameter droplets increased dropwise condensation. This smaller diameter droplets slide faster through the micro-grooved copper surfaces compared to the flat copper plate. As a result, the condensate drainage in modified copper plates is expedited, which improves the condensation behavior of the micro-grooved copper plates. Heat transfer behavior is also studied in terms of heat transfer coefficient. Heat transfer Co-efficient of wedge, sinusoidal and rectangular shaped micro-grooved surfaces are 15-18%, 15-50% and 20-60% higher than flat copper surface at same Sub-cooling temperature. This is due to the decrement of wettability and droplet density in case of modified copper surfaces. Plausible reason for this enhancement has been broadly discussed in this article.