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Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Enhanced gas-liquid absorption through natural convection studied by neutron imaging
Authors: Fumey, Benjamin
Borgschulte, Andreas
Stoller, Sascha
Fricker, Reto
Knechtle, Ralf
Kaestner, Anders
Trtik, Pavel
Baldini, Luca
et. al: No
DOI: 10.1016/j.ijheatmasstransfer.2021.121967
Published in: International Journal of Heat and Mass Transfer
Volume(Issue): 182
Issue: 121967
Issue Date: Jan-2022
Publisher / Ed. Institution: Elsevier
ISSN: 0017-9310
Language: English
Subjects: Liquid absorption; Neutron imaging; Long-term heat storage; Concentration-based convection; Heat and mass exchanger design
Subject (DDC): 621.04: Energy engineering
Abstract: Heat release from absorption storage heat pump by means of absorption of water vapor into aqueous sodium hydroxide is limited by uptake kinetics affecting temperature gain, as well as power- and energy density of the method. Earlier studies pinpoint that natural diffusion alone is not sufficient to reach higher uptake rate, and that the surface to bulk exchange has to be enforced. In this paper, different technical solutions to this problem for the heat storage application are introduced and studied by neutron imaging, enabling visual observation of water vapor uptake and diffusion. The experiments brought to the fore that the buoyancy changes associated with water uptake may be utilized to markedly enhance kinetics. This concept was applied on a vertically installed spiral finned tube operating as heat and mass exchanger for the absorption storage heat pump, also referred to as sorption heat storage. By flooding the space between the spiral fin with absorbent, water absorption into the vertical surface leads to a buoyancy driven movement of the liquid, supplying unspent aqueous NaOH to the vertical surface and exchanging it with the diluted liquid. This is found to increase the rate of absorption markedly. Under realistic heat storage specific operating conditions, a temperature gain of 12.5 K, an active area specific power of 1.28 kW/m2 and an energy density of 243 kWh/m3 in respect to the volume of charged absorbent (greatest volume) is reached. It is proposed that carful design of the spiral finned tube to enhance buoyancy movement will further improve overall sorption heat storage performance.
Fulltext version: Published version
License (according to publishing contract): CC BY 4.0: Attribution 4.0 International
Departement: Architecture, Design and Civil Engineering
Organisational Unit: Centre for Building Technologies and Processes (ZBP)
Appears in collections:Publikationen Architektur, Gestaltung und Bauingenieurwesen

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