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Influence of microstructured surface modifications on the wettability of absorber tubes.

Number: pap. n. 96

Author(s) : TOMFORDE C., LUKE A.

Summary

The permanently proceeding climate change and the scarcity of natural resources require increasing energy efficiency in all technical processes. This aim may be achieved by the intensified utilization of waste heat on a low temperature level which occurs in many different applications. Up to now, this waste heat is emitted unused to the environment in most cases. This waste heat may be used as operating energy for absorption chillers substituting cooling supply with compression cycles. This leads to a lower consumption of primary energy and the overall energy efficiency is increased. Unfortunately, reliability and efficiency of absorption chillers is not competitive with compression chillers. The absorber has been identified as the limiting component of those cycles and the influence of many parameters on the transport processes is not understood so far. The wettability of absorber tubes with different structured surfaces is investigated. Different treatments are used for the surface modification and the roughness of the tubes is varied in a wide range. In a first step, the tube surfaces are characterized by three dimensional topographies, a detailed roughness analysis and the measurement of the surface energy. The dynamic sessile drop method is applied to describe the local wetting behavior of all tube surfaces and the overall wetting of the different structured tube banks is evaluated by high-speed video recordings. Distilled water and aqueous lithium-bromide solution are used as working fluids. The obtained results are discussed and compared with those published in literature and a relation between the micro-structured surface modification, local wetting and overall wetting is established.

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Pages: 10 p.

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Details

  • Original title: Influence of microstructured surface modifications on the wettability of absorber tubes.
  • Record ID : 30013902
  • Languages: English
  • Source: International sorption heat pump conference (ISHPC2014), College Park, United States, March 31-April 2, 2014.
  • Publication date: 2014/03/02

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