An instrument for evaluation of performance of heat dissipative coatings.

An instrument is developed to evaluate the performance of heat dissipative coatings. The instrument has features to measure the apparent emissivity of a given surface under different input power settings. The emissivity of aluminum (Al Q-panel) and copper, as measured from 60-135 degrees C, showed a value of 0.15+/-0.03 and 0.42+/-0.05, respectively, consistent with reported values in literature. The relative emissivity of a heat dissipative coating, called as molecular fan carbon nanotube "MF-CNT," was found to be approximately 0.97. A simple mathematical model is built to evaluate the role of different heat transfer mechanisms (convection and radiation) on cooling performance, and it was observed that convection plays a dominant role in cooling, with more than 90% of heat transferred by convection. In presence of MF-CNT coating, radiation heat transfer increases to approximately 30% and lowers the steady state temperature by 10 degrees C. It is illustrated that radiative cooling could be a significant factor in thermal management.