Henninger S.K.,Fraunhofer Institute for Solar Energy Systems |
Schicktanz M.,Fraunhofer Institute for Solar Energy Systems |
Hugenell P.P.C.,Fraunhofer Institute for Solar Energy Systems |
Sievers H.,Quantachrome GmbH and Co. KG |
Henning H.-M.,Fraunhofer Institute for Solar Energy Systems
International Journal of Refrigeration | Year: 2012
In this first part a comprehensive thermophysical characterisation of six activated carbons - based on coconut, peat and stone coal with focus on thermally driven chillers is reported. Pore and surface analysis are performed using N 2 and CO 2 adsorption. Furthermore the density and heat capacity of the samples is determined. Methanol adsorption measurements for evaporation between -5°C and 35°C and driving temperatures up to 130°C are realized using a thermobalance and evaluated using the Dubinin-Astakhov (DA) approach. Based on the given DA equations, the possible loading lifts for typical applications like 95°-35°-7°C are calculated. The samples show very attractive maximum loading lifts up to 0.385 g g -1. Furthermore the mass and volume specific cooling enthalpy of 244 kJ kg -1 and 126 kJ dm -3 under realistic conditions demonstrates the good performance of this working pair. © 2012 Elsevier Ltd and IIR. All rights reserved.
Reichenbach C.,University of Leipzig |
Kalies G.,University of Leipzig |
Enke D.,University of Leipzig |
Klank D.,Quantachrome GmbH and Co. KG
Langmuir | Year: 2011
In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided. © 2011 American Chemical Society.
Oetzel C.,Quantachrome GmbH and Co. KG |
Klank D.,Quantachrome GmbH and Co. KG
CFI Ceramic Forum International | Year: 2010
Comprehensive particle and pore characterization from starting powder to ceramic green body has been reported. Comprehensive characterization of the particles, the suspensions (with wet methods) and the green bodies is therefore one of the most important tasks in the development of new products, but also for the quality control of raw materials as well as of intermediate and finished products in ceramics. The cast specimens were then dried for 24 hours in air. The suspensions were analyzed with the DT-1201 acoustic spectrometer to determine their dispersive state (particle size distribution in the original slip) and zeta potential. The strong agglomeration tendency in this suspension can have several causes. The exchange of Zr02 with A1203 particles reduced the porosity somewhat and led to a new pore system with much smaller pore widths in the green body. However, the process for the preparation of the green body is not yet sufficiently optimized to completely fill the big pores of the zirconia particles with alumina.
Klank D.,Quantachrome GmbH and Co. KG |
Lohmeier S.,Quantachrome GmbH and Co. KG
Chemie-Ingenieur-Technik | Year: 2012
This article presents a comprehensive overview on the formation and investigation of porous systems and surface area characteristics of micro-, mesoporous zeolitic materials based on aluminum phosphate materials, microporous carbons, building materials in terms of cement stone and natural soil samples. The results of the gas sorption experiments performed on the different materials will be discussed in detail, especially when sorption phenomena like kinetic restricted diffusion, sorption hysteresis and materials where the pore system is undergoing a structural deformation with time can be observed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.