Abstract
Purely heat-driven refrigeration has the potential for high primary-energy efficiency, especially when powered by waste heat or solar thermal sources. This paper presents a novel expression for the ideal adsorption step location as a function of operating conditions. This methodology is then applied to a hypothetical stepwise material to evaluate its intrinsic efficiency. This analysis technique is then extended to allow facile efficiency comparisons for any adsorbent-refrigerant pair using an adsorbent's isotherm and heat of adsorption properties. This work focuses on limitations to efficiency due to the equilibrium thermodynamics. It is found that a stepwise adsorbent can have a single-effect intrinsic efficiency of as high as about 85% of Carnot, assuming typical adsorbent specific heats and uptake capacity. Using these tools, we analyze the maximum ratio of cooling to heat input (coefficient of performance) for two adsorption pairs, zeolite 13X-water and UiO-66-water, which are found to have maximum coefficients of performance of 0.52 and 0.88 for a cold-side temperature of 10 °C and an ambient temperature of 30 °C, respectively. Meanwhile, the maximum fraction of Carnot cooling is 37% for zeolite 13X-water and 67% for UiO-66-water. Moreover, these peak fractions of Carnot occur at much higher regeneration temperatures for 13X (196 °C) than for UiO-66 (60 °C). These two materials could be coupled in a two-stage cascading triple-effect adsorption cycle that operates with a combined coefficient of performance of 1.50 at a regeneration temperature of 196 °C, a cold-side temperature of 10 °C, and an ambient temperature of 30 °C.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Langmuir : the ACS journal of surfaces and colloids
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.