Abstract
This paper introduces the results of an experimental study on the adsorption and desorption kinetics of a commercially available, open-structured asymmetric plate heat exchanger adapted to act as an adsorber/desorber for the application in adsorption heat transformation processes. In addition, a volumetric large temperature jump (V-LTJ) kinetic setup was applied to measure the adsorption and desorption kinetics of a small-scale adsorbent sample prepared dedicatedly to be representative for the adsorbent domain inside the investigated adsorber plate heat exchanger (APHE). All kinetic results of the small-scale adsorbent sample and the APHE were fitted into exponential forms with a single characteristic time constant (τ) with a coefficient of determination (R2) better than 0.9531. A very good matching between the small-scale and full-scale adsorption kinetic measurements was obtained, with an average relative deviation of 12.3% in the obtained τ-values. In addition, the kinetic data of the small-scale adsorbent sample were utilized for estimating the expected specific instantaneous and moving average powers of the evaporator/condenser heat exchanger. The average relative deviation (ARD) between the moving average specific evaporator powers obtained from the small-scale and the full-scale measurements amounts between 5.4 and 15.1%.
Highlights
The adsorber/desorber heat exchanger (Ad-HEx) is the core component of an adsorption system
The adsorbent’s representative sample is designed to predict the adsorption and desorption kinetics of the adsorber plate heat exchanger (APHE) introduced in this study
The instantaneous as well as the moving average evaporator and condenser powers estimated from the adsorption and desorption kinetic results of the smallscale adsorbent sample are compared to the powers obtained from the evaporator/condenser unit, against which the introduced APHE has been experimentally tested at the previously mentioned operating conditions
Summary
The adsorber/desorber heat exchanger (Ad-HEx) is the core component of an adsorption system. The design of the test frame, in which the small-scale adsorbent grain sample has been tested, has been carried out with a special care to mimic both heat and mass transfer characteristics of the adsorbent domain inside the introduced plate heat exchanger (Mikhaeil et al, 2020). As the maximum expected differential water uptake from the utilized microporous silica gel (Siogel of Oker Chemie, Germany) under the tested operating conditions does not excess 25 g/100g, the mass of the samples that will be tested in the small-scale sorption kinetics’ setup is limited to 320 mg to guarantee the adsorption or desorption measurements to be carried out under quasi-isobaric (Δp < 2 mbar) conditions (Aristov et al, 2008) Based on this limitation of the sample mass, and its volume inside the test frame, the width of the sample has been determined to 3 mm. The accuracy of the applied individual sensors and the accumulated accuracy are introduced in Supplementary Material
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