A Detailed Thermodynamic Study of Rayleigh-Benard Cells

Systems that are out-of-equilibrium and exhibit complex patterns are difficult to characterize. These systems are thermodynamically open, thereby constantly exchanging heat and matter with the surrounding. In order to be able to systematically and rigorously characterize such a system we present an experimental study of an out-of-equilibrium thermodynamic system, the Rayleigh-Benard convection cells. When a thin layer of liquid is evenly heated from the bottom the liquid tends to self-organize into patterns of hexagonal cells or a series of rolls. The cells or rolls are an outcome of an upward flow of the hot layer of the liquid from the bottom, and a downward flow of the cool layer of the liquid from the top along with the competing effects of viscosity and thermal gradient. The goal of this presentation is to measure the flow of energy through the system and be able to quantify it, along with steady state measurements of the temperature fluctuation, entropy and internal work calculation by infrared imaging as a function of fluid viscosity and thickness over a wide range of heat input. The resulting thermal patterns will be interpreted in terms of a balance between internal entropy and work.