Viessmann Werke Allendorf GmbH

Allendorf, Germany

Viessmann Werke Allendorf GmbH

Allendorf, Germany
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Freni A.,CNR Institute of Advanced Energy Technologies Nicola Giordano | Frazzica A.,CNR Institute of Advanced Energy Technologies Nicola Giordano | Dawoud B.,Viessmann Werke Allendorf GmbH | Chmielewski S.,Viessmann Werke Allendorf GmbH | And 2 more authors.
Applied Thermal Engineering | Year: 2013

This paper presents novel experimental methods for verification of both hydrothermal and mechanical stabilities of adsorbent coatings. Experiments have been carried out on zeolite-based coatings over aluminum substrates, prepared by a dip-coating technique developed at CNR-ITAE. Hydrothermal aging of several adsorbent coatings is ongoing. Adsorption and structural stability of some samples under test was successfully verified after 35000 aging cycles by isobars measurement and XRD analysis. Mechanical properties of coatings have been evaluated by applying different typologies of static and dynamic mechanical stresses. Results obtained have been compared with those achieved by subjecting adsorbent coatings prepared by Mitsubishi Plastic Incorporation (MPI) to the same characterization protocol. The comparison between the two types of coating returned that MPI coatings posses similar thermal stability and better mechanical strength than CNR-ITAE coatings. © 2012 Published by Elsevier Ltd.


The main objective of this work is to introduce an innovative hybrid heating appliance incorporating a gas condensing boiler and a zeolite-water adsorption heat pump. The condensing boiler is applied to drive the zeolite-water heat pump for the heating base-load and to assist the heat pump in the so called "mixed operation" mode, in which both the heat pump and the condensing boiler are working in series to cover medium heating demands. Peak heating demands are covered by the condensing boiler in the so called "direct heating" mode. The three operation modes of the hybrid heating appliance have been technically described. In addition, the laboratory test conditions for estimating the seasonal heating performance according to the German Guideline VDI 4650-2 have been introduced. For both heating systems 35/28 °C and 55/45 °C, which represent the typical operating conditions of floor and high temperature radiating heating systems in Europe, seasonal heating gas utilization efficiencies of 1.34 and 1.26 have been measured, respectively with a ground heat source. In two field test installations in one-family houses in Germany, the introduced heating appliance showed 27% more seasonal gas utilization efficiency for heating and domestic hot water production, which is equivalent to a CO2-emission reduction of 20% compared to the gas condensing boiler technology. © 2014 Elsevier Ltd. All rights reserved.


Dawoud B.,Viessmann Werke Allendorf GmbH
Applied Thermal Engineering | Year: 2013

A possibility to enhance both heat and mass transfer characteristics of an adsorber heat exchanger is to apply the adsorbent directly to its surface in form of a consolidated layer. As the majority of the available publications on the effect of both coating technology and adsorbent layer thickness on the adsorption kinetics deals with small scale adsorbent samples, the results obtained can only represent the best case design of an adsorber heat exchanger. This article presents, therefore, a comparison between the adsorption kinetics of water vapour on small as well as two different full scale coated adsorber heat exchanger types with AQSOA-Z02 layers of Mitsubishi Plastics Incorporation under quasi isobaric conditions of adsorption heat pumps. The small scale coated samples have a zeolite dry mass of 200 mg and layer thicknesses of 200, 300 and 500 μm while the full scale adsorbers have a coated zeolite mass between 1.5 and 2.5 kg and layer thicknesses of 150, 200, 300, 400 and 500 μm. In the investigated adsorption heat pump module, up to 52.7 and 57.3% of the equilibrium differential water loading measured with the small scale coated substrates have been obtained after an adsorption-evaporation times of 300 and 600 s, respectively. © 2012 Published by Elsevier Ltd.


In its endeavours to safeguard the long-term supply of natural gas, the German gas industry draws on fuel from different sources. In addition, an increasing proportion of alternative gases, such as LNG, EASEE gas and bio-enriched natural gas will be fed into the supply networks. The resulting wide range of gas qualities can only be accommodated by gas condensing boilers equipped with conventional air-gas mixers with some considerable conversion effort. Our response to this challenge is the self-calibrating Lambda Pro Control combustion controller. It makes all combustion-related adjustments of the appliance during commissioning as well as any manual alteration in the case of changes in the gas quality unnecessary. Since its launch in 2005, the Lambda Pro Control has proven its capability in more than 500.000 gas condensing boilers, with excellent results.


Dawoud B.,Viessmann Werke Allendorf GmbH | Sohel M.I.,University of Canterbury | Freni A.,CNR Institute of Neuroscience | Vasta S.,CNR Institute of Neuroscience | Restuccia G.,CNR Institute of Neuroscience
Applied Thermal Engineering | Year: 2011

This paper presents a theoretical model for predicting the effective thermal conductivity of wetted zeolite. The model comprises the thermal conductivities of the zeolite crystal as well as of the adsorbed water. The temperature dependence of both thermal conductivities is considered. Moreover, the contribution to the effective thermal conductivity due to vapor conductance is also taken into account. The effective thermal conductivity of 4A zeolite-water is measured by transient "hot wire" method under various conditions of vapor pressure, temperature and water loading. The measurement ranges are chosen according to the operating conditions of a typical adsorption cooling cycle. The experimentally measured data are fitted to the proposed theoretical model. The maximum deviation between the experimental results and the theoretical values is estimated to be ±5.8%. The validated model is used to realize a zeolite 4A conductivity chart, which represents an useful tool for thermal design of adsorption machines. © 2011 Elsevier Ltd. All rights reserved.


Modern gas condensing technology has not only proven to be one of the most effi cient ways of producing heat, but also enables appliance dimensions to be kept to an absolute minimum. In fact, wall mounted gas condensing boilers and gas condensing storage combi boilers are constantly being redesigned with more compact dimensions and a lower water content. In conjunction with the low heat loads in new builds and existing buildings in which the energy supply has been modernised, higher demands are being made of the ability of wall mounted and storage combi boilers to adapt to different operating states, especially to partial load operation. New control strategies not only enable low cycling, but also increase appliance effi ciency and comfort levels.

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