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Numerical layer optimization of aluminum fibre/SAPO-34 composites for the application in adsorptive heat exchangers.

Author(s) : FÜLDNER G., SCHNABEL L., WITTSTADT U., et al.

Summary

The design of the adsorptive heat exchanger (AdHex) is a key issue in the development of adsorption heat pumps and chillers. The aim is to increase power densities without decreasing the COP of the machine. One focus has been the development of adsorbent materials with a high water loading at driving temperatures below 100°C. SAPO-34 has proved to be a very promising material for these applications. As a consequence, the design of the AdHex has to be adapted to the needs as well: more heat must be removed and supplied more quickly from and into the active material, while for high COP a good mass ratio between adsorbent and heat exchanger has to be realized. For this purpose, a new composite material has been developed. It consists of aluminum fibres realizing a high volumetric surface at high porosities, good thermal conductivity and good thermal contact to a metal lamella. These fibres then are coated with SAPO-34 by direct crystallization (Bauer et al., 2009). Results of adsorption kinetics measurements and simulations on lab scale samples of such composites show a fast uptake at a very good mass ratio. Heat and mass transport coefficients of the samples are obtained by fitting a bidisperse non-isothermal model to the transient adsorption kinetics in large pressure jump experiments. Additionally, heat conductivity, heat capacity, density, pore size and porosity are determined. With the obtained physical parameters cycle simulations are performed and the geometric dimensions of the composite layer are optimized with respect to a high volume specific power (> 250 W per liter of AdHex volume) at good cooling COP values (>0.5 without heat recovery) at moderate cycle conditions (15/40/95°C).

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Pages: 533-542

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Details

  • Original title: Numerical layer optimization of aluminum fibre/SAPO-34 composites for the application in adsorptive heat exchangers.
  • Record ID : 30001251
  • Languages: English
  • Source: Sources/sinks Alternative to the Outside Air for Heat Pump and Air-conditioning Techniques (Alternative Sources - AS), Padua, Italy, April 5-7, 2011. / International Sorption Heat Pump Conference (ISHPC11), Padua, Italy, April 6-8, 2011.
  • Publication date: 2011/04/06

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