Solar Thermal Technology

Our group is working on multiple, collaborative projects related to concentrated and unconcentrated solar thermal technology for electricity production, chemical processing, and water and space heating. Examples include development of a micro-pin based solar receiver for heating supercritical carbon dioxide and exploiting advanced manufacturing techniques to develop components for modular chemical processing systems powered by concentrated sunlight. Our interest is in addressing the coupled thermal hydraulic/materials/design/manufacturing problems to make solar thermal more economically viable. Work in this area is being sponsored by the US DOE Solar Technology Office and the RAPID Institute.

Energy Storage

Low cost, grid-scale energy storage is critical for the increased deployment of renewable electricity generation. We are investigating different thermal and thermochemical storage technologies and how they will interact with different generation sources (solar and nuclear) and different end uses such as supercritical CO2 power cycles, high temperature industrial processes, and lower temperature processes for space and water heating. Shown above is a chemical heat pump for thermochemical energy storage and upgrade.

Work in this area has been sponsored by the US DOE Nuclear Energy, Solar Energy Technology, and Building Technology offices.

High Temperature Heat Exchangers

High temperature heat exchanger development is an inherently multi-disciplinary problem. We are working on several projects investigating new materials, manufacturing methods and thermal/hydraulic designs to enable low cost, reliable, high temperature heat transfer in various systems. Ultimately, this work will lead to more efficient production of electricity, heating, cooling, and chemical products.

Work in this area is being sponsored by the US DOE Solar Technology Office and the RAPID Institute.

Building Energy Systems

Buildings consume nearly 40% of global energy, mostly for space heating, cooling, and water heating. Our group is interested in near-term technology development through investigations of new working fluids and heat exchangers for vapor compression systems, and continued investigation on longer term non-vapor compression technology for producing heating, cooling and power. Examples include membrane based systems (above), which can drastically reduce energy consumption and eliminate he need for environmentally harmful working fluids.

Work in this area has been sponsored by the US DOE Building Technology Office, ASHRAE, and industrial partners.

Multiphase Heat and Mass Transfer

Multiphase flow and in-tube condensation heat transfer is critical to many industries including power generation, HVAC&R, transportation, and chemical processing. As concern over energy consumption and the environmental impact of certain synthetic fluids intensify, there has been an increased adoption of mini- microchannel heat exchangers and new working fluids (e.g., hydrocarbons, carbon dioxide, ammonia, zeotropic mixtures). Microscale devices offer the potential for reduced component size and working fluid inventory. However, the two-phase flow and condensation mechanisms for these different fluids and geometries are not well understood. This work seeks to develop an improved understanding of the underlying flow mechanisms and leverage the insights into the design of compact, efficient heat transfer equipment by:

  • Understanding flow morphology and transitions at very small diameters and low mass flux, representative of actual operating conditions

  • Validate design tools for novel working fluids and mixtures to mitigate environmental impact while maintaining good thermal performance

  • Develop versatile models capable of predicting condensation heat transfer and pressure drop for a wide range of fluids and conditions

  • Demonstrate the reduction in cost, size and energy consumption of microchannel based components in energy systems

Supercritical Heat Transfer

Supercritical fluids operate above the critical temperature and pressure, where there is no distinct liquid or gas phase. Unlike the familiar phase change process in conventional energy systems, supercritical fluids undergo a continuous, non-isothermal transition from “gas-like” to “liquid-like” properties during cooling. In a region near the critical point, significant spikes in specific heat and other thermophysical properties can enhance heat transfer. Supercritical Brayton cycles have emerged as a national strategic focus for highly efficient solar thermal, geothermal, nuclear, and clean fossil energy systems. Key advantages of these cycles include improved thermal efficiency, smaller components, and a reduction of fresh water consumption in electricity production, which presently accounts for 45% of U.S. fresh water withdrawals. Realizing these gains requires optimized thermal fluid design of supercritical heat transfer devices. Supercritical heat exchanger design has primarily relied on purely empirical correlations that have been specifically tailored for supercritical carbon dioxide (sCO2) in round tubes. Without a physical basis, the existing design methods cannot be generalized to systems with new geometries or working fluids. Examples include microgap pin fin structures, organic fluids, and multi-constituent mixtures, which have shown potential for producing even higher system efficiencies for systems in power generation, HVAC&R, waste heat recovery, aersopace, carbon sequestration, electronics cooling, and other industrial processes.

Our work in the HEATER Lab is focused on experimentally isolating of the different mechanisms that govern supercritical heat transfer, including the effects of buoyancy, fluid properties, and geometry. The end goal of this work is to develop mechanistic based engineering design tools for predicting supercritical heat transfer during heating and cooling in advanced micro geometries for a wide range of working fluids and condition