Elastocaloric cooling is a new alternative solid-state cooling technology undergoing early stage research and development. This study presents a comprehensive review of key issues related to achieving a successful elastocaloric cooling system. Fundamentals in elastocaloric materials are reviewed. The basic and advanced thermodynamic cycles are presented based on analogy from other solid-state cooling technologies. System integration issues are discussed to characterize the next generation elastocaloric cooling prototype. Knowledge acquired from the elastocaloric heat engines is provided as the basis for the design of cooling system configuration. Commercially available drivers enabling proper compression and tension are also presented. A few performance assessment indices are proposed and discussed as guidelines for design and evaluation of future elastocaloric cooling system. A brief summary of the up-to-date elastocaloric cooling prototypes is presented as well.

To avoid global warming potential gases emission from vapor compression air-conditioners and water chillers, alternative cooling technologies have recently garnered more and more attentions. Thermoelastic cooling is among one of the alternative candidates, and have demonstrated promising performance improvement potential on the material level. However, a thermoelastic cooling system integrated with heat transfer fluid loops have not been studied yet. This paper intends to bridge such a gap by introducing the single-stage cycle design options at the beginning. An analytical coefficient of performance (COP) equation was then derived for one of the options using reverse Brayton cycle design. The equation provides physical insights on how the system performance behaves under different conditions. The performance of the same thermoelastic cooling cycle using NiTi alloy was then evaluated based on a dynamic model developed in this study. It was found that the system COP was 1.7 for a baseline case considering both driving motor and parasitic pump power consumptions, while COP ranged from 5.2 to 7.7 when estimated with future improvements.

Thermoelastic cooling is a recently proposed, novel solid-state cooling technology. It has the benefit of not using high global warming potential (GWP) refrigerants which are used in vapor compression cycles (VCCs). Performance enhancements on a thermoelastic cooling prototype were investigated. A few novel design options aiming to reduce the cyclic loss were proposed. It was found that the maximum temperature lift increased from 6.6 K to 27.8 K when applying the proposed novel designs, corresponding to 0 to 152 W cooling capacity enhancement evaluated under 10 K water-water system temperature lift. In addition, a multi-objective optimization problem was formulated and solved using the genetic algorithm to maximize the system capacityACCEPTED MANUSCRIPT 2 and coefficient of performance (COP). With all the novel designs, the optimization could further enhance 31% COP, or 21% cooling capacity, corresponding to COP of 4.1 or 184 W maximum cooling capacity. Nomenclature Symbols A area [m 2 ] COP coefficient of performance [-] c p specific heat [J·g -1 ·K -1 ] D diameter [m] GWP global warming potential HR heat recovery HTF heat transfer fluid h heat transfer coefficient [W·m -2 ·K -1 ] ID internal diameter [m] k thermal conductivity [W·m -1 ·K -1 ] L length [m] N quantity [-] OD outside diameter [m] PEEK polyether-ether-ketone ra nitinol heat transfer area to volume ratio [m -1 ] SMAs shape memory alloys sec second T temperature [K] M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 t time, or duration [sec] t* heat recovery duration coefficient [-] u fluid mean velocity [m·s -1 ] VCC vapor compression cycle α thermal diffusivity [m 2 ·s -1 ] β tubes holder contact area ratio [-] δ equivalent thickness [m] κ thermal mass factor ρ density [kg·m -3 ]

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