Enhanced infrared-large-temperature-jump method for multi-layer adsorption kinetics estimation

Applied Thermal Engineering, vol. 289, pp. 129619

Abstract

Adsorption chillers can recover industrial low-temperature waste heat to provide sustainable cooling. To improve power density and economic viability, numerous studies optimized the adsorption chiller design based on dynamic process models. Dynamic process models require sound kinetic models for heat and mass transfer. Adsorption kinetics can be assessed with the infrared-large-temperature-jump method (IR-LTJ). The effective heat and mass transfer coefficients are typically estimated from monolayer sorbent experiments, limiting their applicability to multi-layer adsorber heat exchangers, which are used in practice. Hence, this work presents an enhanced IR-LTJ method to analyze multi-layer adsorption kinetics. Based on the existing inert IR-LTJ approach, this work proposes an additional step to improve the extrapolation of the kinetic coefficients: Conducting inert IR-LTJ experiments across multiple sorbent layers to ascertain an effective heat transfer coefficient between them. The method was validated with the working pair silica gel 123 and water. Two-, four- and eight-layer IR-LTJ experiments were conducted for validation. By adding an effective heat transfer coefficient between the layers, the root-mean-square-error (RMSE) between model and experiment could be reduced by at least 28 % for eight-layer IR-LTJ experiments compared to the existing method. For two- and four-layer IR-LTJ experiments the RMSE could be reduced by at least 34 % and 42 %, respectively. Therefore, a better extrapolation of adsorption kinetics was achieved for a variable number of sorbent layers. The estimated coefficients provide a more detailed representation of the impact of heat exchanger design on the adsorption kinetics.

Authors 7

1. Taiba Aziz corresponding Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

2. Mirko Engelpracht Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Adsorbus GmbH, 13509, Berlin, Germany

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

3. Patrik Postweiler Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

4. Caspar Schwarz Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

5. Daniel Rezo Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

6. Carsten Wedler Aachen Institute of Technical Thermodynamics

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany

7. Niklas V. von der Assen corresponding