Date on Master's Thesis/Doctoral Dissertation

5-2024

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Bhatia, Bikram

Committee Member

Kate, Kunal

Committee Member

Chen, Yanyu

Committee Member

Sumanasekera, Gamini

Author's Keywords

Barocaloric effect; solid state refrigeration; Barocaloric heat pump; thermodynamic and heat transfer; next generation refrigeration

Abstract

Solid-state refrigeration offers a promising alternative to traditional vapor compression systems that are relatively inefficient, unreliable, and have a high global warming potential. Various solid-state cooling technologies, including those based on electrocaloric, magnetocaloric, and elastocaloric effects have been investigated in the recent past. However, concerns regarding their efficiency, scalability and cost remain. Refrigeration and heat pump technologies based on the barocaloric effect (temperature/entropy change due to hydrostatic pressure) hold great promise but have received comparatively less attention. Barocaloric heating/cooling based on low cost, compressible soft materials with large barocaloric response have the potential to pave the way for efficient, scalable, and affordable solid-state heat pumps. This dissertation investigates barocaloric heat pumps based on soft materials – beginning with the introduction of high-performance barocaloric refrigerants and culminating in a prototype barocaloric solid-state heat pump. The first project identified soft barocaloric refrigerants that demonstrate high thermal conductivity while showing large barocaloric response that can be feasibly utilized in a barocaloric cooling device. The second project investigated the barocaloric properties of composite materials with the addition of reduced graphene oxide – a high thermal conductivity filler. The third project developed a numerical model that combined the thermal, mechanical and barocaloric response of materials for a prototypical barocaloric solid-state refrigeration device based on the reversed Brayton cycle. This model that combined thermodynamics and heat transfer allowed us to investigate the impact of operating conditions and material properties on the heat pump performance – demonstrating significant improvements in cooling power and coefficient of performance (COP). Finally, the last project integrated our understanding of the barocaloric response of materials and device performance to develop a first-of-its-kind barocaloric solid-state heat pump prototype. Using natural rubber as the refrigerant material, a piston-cylinder arrangement, and ethylene glycol as the heat transfer fluid, we demonstrated a COP > 4, positioning it competitively alongside vapor compression systems. This dissertation lays the groundwork for barocaloric cooling and heat pumping, which could enable next-generation refrigeration and air conditioning systems.

Available for download on Monday, November 11, 2024

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