Imaging Velocimetry Measurements for Entropy Production in a Rotational Magnetic Stirring Tank and Parallel Channel Flow

Greg Naterer,Olusola Adeyinka

doi:10.3390/e11030334

Abstract

An experimental design is presented for an optical method of measuring spatial variations of flow irreversibilities in laminar viscous fluid motion. Pulsed laser measurements of fluid velocity with PIV (Particle Image Velocimetry) are post-processed to determine the local flow irreversibilities. The experimental technique yields whole-field measurements of instantaneous entropy production with a non-intrusive, optical method. Unlike point-wise methods that give measured velocities at single points in space, the PIV method is used to measure spatial velocity gradients over the entire problem domain. When combined with local temperatures and thermal irreversibilities, these velocity gradients can be used to find local losses of energy availability and exergy destruction. This article focuses on the frictional portion of entropy production, which leads to irreversible dissipation of mechanical energy to internal energy through friction. Such effects are significant in various technological applications, ranging from power turbines to internal duct flows and turbomachinery. Specific problems of a rotational stirring tank and channel flow are examined in this paper. By tracking the local flow irreversibilities, designers can focus on problem areas of highest entropy production to make local component modifications, thereby improving the overall energy efficiency of the system.

Highlights

IntroductionTo information/coding theory, economics and biology, the many applications of entropy are widespread
From engineering fluid mechanics, to information/coding theory, economics and biology, the many applications of entropy are widespread
The conversion algorithm for measured entropy production and flow irreversibilities was validated against analytical entropy production results for water flow in a parallel channel

Summary

Introduction

To information/coding theory, economics and biology, the many applications of entropy are widespread. Entropy serves as a key parameter in reaching the upper limits of performance and quality in many engineering technologies It can shed new light on various flow processes, ranging from optimized flow configurations in an aircraft engine, to highly ordered crystal structures (low entropy) in a turbine blade, and other applications [1,2]. Exergy and entropy calculations can identify the loss of work potential within each sub-system and fluid flow process during an aircraft’s operation. This would provide the designer with a systematic way of identifying and targeting those areas incurring the most significant losses. In this way, economic decisions could be directly linked to work potential and flow irreversibilities. Moorhouse and Suchomel [5] reported that flow exergy provides a unifying framework and a set of metrics to more effectively analyze aircraft sub-systems

Methods

Results

Conclusion