Experimental Determination of Entropy Generation Rate Using Particle Image Velocimetry

Abstract

As Particle Image Velocimetry (PIV) matures, new techniques have been developed for flow analysis that exploit PIV. One such recent use is in determining the underlying mechanisms of energy losses in fluidic systems. Often times, a First Law of Thermodynamics (FLT) approach is taken to determine the energy losses in a given fluidic system. However, a Second Law of Thermodynamics (SLT) approach allows for much greater detail of the energy losses to be determined. This paper will characterize the use of experimental PIV in conjunction with the SLT at the University of Central Oklahoma. A PIV apparatus can be used to observe the flow field in a given region of interest (ROI) of a fluidic system. This paper focuses on the use of PIV in conjunction with the SLT to determine the viscous dissipation rate and entropy generation rate of specified ROIs for dividing laminar flow in square ducts. Computational Fluid Dynamics (CFD) software is employed for simulation and experimental verification. A range of Reynolds numbers in the laminar regime (1–100) are used as a basis for determining volumetric flow rates through the system that are commonly found in micro-scale applications. The ROIs investigated here cover simple flow fields, where the results are compared to known analytical solutions derived for fully-developed flow in square ducts. The ROI is then focused on areas of greater interest that are internal and adjacent to a dividing flow geometry. CFD results have been used to calculate the entropy generation rate in a given dividing flow geometry and then compared to experimental results. Experimentally-based maps of viscous dissipation rate and entropy generation rate of the system are derived for analysis of sources of entropy generation.