Title:

A View of Thermophysics and Thermal Systems

Speaker:

Dr. Ian Bell

Affiliation:

National Institute of Standards and Technology

When:

Tuesday, February 25, 2020 at 11:00:00 AM   Add to Calendar

Where:

MRDC Building, Room 4211

Host:

Dr. Satish Kumar
satish.kumar@me.gatech.edu

Abstract

In this presentation, my previous and present research activities are summarized, describing some common themes emerging from these studies, especially the integral nature of thermophysical properties to the analysis of the next generation of energy systems. An initial research focus was on improving and maintaining the efficiency of thermal systems, both from the standpoint of understanding the effects of faults on the system, for example, air-side particulate fouling of heat exchangers as well as not-in-kind solutions to improve the efficiency of vapor compression cooling systems, most especially the liquid-flooded compression approach to approach isothermal compression. As part of that work, detailed study of scroll compressors was carried out, setting the stage for what would become the open-source PDSim library for the simulation of positive-displacement compressors and expanders. In order to design and optimize novel components and systems or investigate new theoretical phenomena, it is necessary to have a reliable understanding of the properties of the working fluids, characterized by models. These models are multivariate correlations of experimental data and are usually totally empirical in nature, or at least semi-empirical with a theoretical foundation and adjustable parameters. Global optimization of the adjustable parameters of the models can be challenging, and model parameter optimization approaches are described for a range of applications. Once a thermophysical property model has been developed, dissemination is done through a software package. The CoolProp library, of which I was the primary developer, is an open-source thermophysical property library which includes reference models and selected new models and the ability to implement many other models in a flexible framework. A key challenge is the numerical routines needed in order to carry out the non-linear rootfinding problems at the heart of the evaluations, and some recent numerical approaches for quasi-guaranteed rootfinding are explained. In recent years, a primary research direction has been an investigation of transport properties, shear viscosity, thermal conductivity, diffusivity, and their link to the residual or excess entropy. This link has been investigated for simple systems of atomic fluids, Lennard-Jones particles, and molecular fluids. The consistent behavior is that for fluids with neither strong hydrogen bonding nor relevant quantum effects, the residual entropy collapses most of the scaled transport properties over much of the phase diagram. Advances in isomoph theory explain why this behavior should be seen, but the collapse appears to hold for many systems even when the theory is not applicable, which merits further research.

Biography

Ian Bell received his B.S.M.E from Cornell University in 2006, and his Ph.D. in Mechanical Engineering from Purdue University in 2011, followed by a postdoctoral research appointment at the University of Liege, Belgium. He is presently a Mechanical Engineer at the National Institute of Standards and Technology in Boulder, Colorado. He is the author of 40 peer-reviewed publications as well as more than 40 other works, and is the primary developer of the CoolProp thermophysical property library, and a developer of the NIST REFPROP property library. He was recently recognized as an emerging investigator by the Journal of Chemical and Engineering Data. His current research interests include a fundamental interrogation of transport properties from the standpoint of entropy, global parameter optimization of property models, and the thermophysical properties of novel working fluids for thermal systems. A unifying theme is an emphasis on the development and application of novel computational codes and a focus on open-source approaches to improve reproducibility of academic and industrial research.

Notes

Refreshments will be served.