Publication Date

12-2020

Date of Final Oral Examination (Defense)

12-1-2020

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Mechanical Engineering

Department

Mechanical and Biomechanical Engineering

Supervisory Committee Chair

Todd Otanicar, Ph.D.

Supervisory Committee Member

Eric Jankowski, Ph.D.

Supervisory Committee Member

Krishna Pakala, Ph.D.

Abstract

Concentrating solar power is an emerging renewable energy source. The technology can collect and store thermal energy from the sun over long durations, generating electricity as needed at a later time. Current CSP systems are limited to a maximum operational temperature due to constraints of the working fluid, which limits the maximum possible efficiency of the system. One proposed pathway forward is to utilize a gas phase for the working fluid in the system such as supercritical carbon dioxide.

A composite gas phase modular receiver is being developed by researchers at Boise State University and the University of Tulsa. The receiver uses supercritical carbon dioxide as the working fluid, which can operate at temperatures greater than 1000 ˚C. The unique carbon-carbon composite material has high thermal conductivity and is structurally durable at extreme temperatures.

A model has been developed in this work to simulate the thermal and hydraulic performance of a composite receiver unit cell. The model is built as a thermal resistance network that solves more quickly than traditional computational fluid dynamics simulations. The thermal and hydraulic models are compared with CFD simulations and show close agreement over a wide range of inlet velocities and path architectures.

A genetic algorithm has been developed to optimize the design of the receiver. The algorithm optimizes the fluid channel diameter, inlet velocity, and the path architecture design of a unit cell. The optimization scheme weighs the thermal performance of the receiver with the hydraulic performance, maximizing the thermal efficiency and minimizing the pressure drop. The nominal strain is also calculated and constrained. The algorithm produces an optimal design from a constrained set of architectures. The optimal design is a simple three-channel parallel path with an acceptable pressure drop, less than 17 kPa. The thermal efficiency of the design is 75.6% with a 1,000,000 W/m2 solar flux and the nominal strain is an allowable 0.03%. Future work will be done to expand the path design space and remove arbitrary constraints from the optimization process.

DOI

10.18122/td/1761/boisestate

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