Zeolite NaY-Copper Composites Produced by Sintering Processes for Adsorption Heat Transformation—Technology, Structure and Performance

Abstract

In adsorption heat pumps, the adsorbent is typically combined with heat conducting structures in order to ensure high power output. A new approach for the direct integration of zeolite granules into a copper structure made of short copper fibers is presented here. Zeolite NaY granules with two different grain sizes are coated with copper fibers and powder and sintered to larger structures. The sorption dynamics of these structures were measured and evaluated in terms of heat and mass transfer resistances and compared to the loose grain configuration of the same material. We found that the thermal conductivity of such a composite structure is approximately 10 times higher than the thermal conductivity of an adsorbent bed with NaY granules. Sorption equilibrium measurements with a volumetric method indicate that the maximum uptake is not altered by the manufacturing process. Furthermore, the impact of the adsorbent–metal structure on the total thermal mass of an adsorption heat exchanger is evaluated. The price of the superior thermal conductivity is a 40% higher thermal mass of the adsorption heat exchanger compared to the loose grain configuration.

Adsorption Dynamics and Hydrothermal Stability of Mofs Aluminium Fumarate, Mil-160 (Al), and Cau-10-H, and Zeotype Tiapso for Heat Transformation Applications

“…Quantitative characterization of the samples before and after hydrothermal stress test was carried out on the kinetic measurement set-up of Fraunhofer ISE [25,28,39]. In contrast to the cycle test rig, volumetric measurement of the adsorbed or desorbed water vapour quantity is possible.…”

“…Subsequently, small pressure jumps are performed until the sample is nearly completely saturated. During LTJ and SPJ measurements the surface temperature is measured contactless by an accurate infrared sensor [25,39].…”

“…Further details of the measurement set-up and methods used can be found in previous publications [25,28,39].…”

“…To overcome this limitation, a method to evaluate heat and mass transfer resistances was developed in the last years [29,[37][38][39] and used to calculate these resistances for small-scale samples [18,21,29,[37][38][39], adsorption heat exchangers [40], and adsorption modules [41,42]. The obtained results indicate that with a given overall heat and mass transfer resistance the adsorption dynamics will depend only on the driving temperature difference.…”

“…Thus, evaluating the heat and mass transfer resistances is a more independent measure than the characteristic times. As the literature review of the relevant sources on heat and mass transfer resistances of small-scale samples [18,21,29,[37][38][39] shows, no data has been published on the impact of hydrothermal stress on the heat and mass transfer resistance of shaped adsorbents. Furthermore, the precise evaluation of the heat and mass transfer resistances requires a detailed and properly fitted adsorption equilibrium model based on several isotherms or isobars from adsorption equilibrium measurements.…”