A. Rysanek1* and S. J. Harrison1
1 Solar Calorimetry Lab, Department of Mechanical and Materials Engineering, Queen’s University,

Kingston, Ontario, Canada K7L 3N6

Corresponding Author, rysanek@me. queensu. ca

Abstract

A prior study has validated the Short-Term Thermal Stores (STTSs) in use at the Drake Landing Solar Community in Okotoks, Alberta, Canada against various CFD modelling schemes. In this work, a set of alternative designs to the STTSs is developed in CAD, and further evaluated using CFD. The alternatives designs incorporate the use of large baffles to direct flow and encourage stratification. The designs are simulated under three charging modes: constant inlet temperature and flow rate, constant inlet temperature and variable flow rate, and variable inlet temperature and flow rate based on an energy profile. A proposed characterization index, deemed in this paper as the Exergy Charge Ratio (^Cr), has been mathematically derived and also applied to this work. Initial results indicate that the tj^Cr may improve the assessment of mixing within a thermal energy store at the early stages of charging. The research may be of significant interest for future applications requiring large thermal energy stores, such as solar district heating networks, or industrial heating processes. Keywords: Thermal storage, exergy (available energy), solar district heating, CFD

1. Introduction

1.1. Background

Prior studies have highlighted the applicability of Computational Fluid Dynamics (CFD) to model the transient behaviour of thermal energy stores [1][2].Among the benefits of flow visualization, the finite volume discretization inherent to CFD allows for the effective analysis of a thermal energy store (TES) using the Second Law of Thermodynamics, whereby quantifiable variables, such as the internal entropy within a TES, can be more easily assessed than in a laboratory setting. This study will provide another practical application of CFD as a design tool for thermal energy stores, using the Drake Landing Solar Community in Okotoks, Alberta, Canada, as a case example.