Publication: Thermo-fluid dynamic evaluation of components in adiabatic absorption systems
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2009
Defense date
2009-07-28
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Abstract
In this PhD thesis, a facility for experimental evaluation of innovative components
forming part of a single effect H20-LiBr adiabatic absorption chiller is analyzed. The
adopted methodology has been mainly experimental. Plate heat exchangers functioning
as generator, solution heat exchanger, condenser and subcooler have been incorporated
in the design. Two adiabatic absorber configurations, droplets and liquid sheets, were
tested and evaluation parameters were experimentally determined.
Overall test facility performance is analyzed in the first stage of the research. The
preliminary analysis gives an idea about the operational features of the machine, which
allow subsequent detailed components analysis. This analysis is oriented to the
interpretation of experimental data including the particular features, in both design and
operation, of the facility here presented: study of evaporators’ efficiency, solution heat
exchanger efficiency and thermal losses. Performance parameters, cooling capacity and
COP, are expressed in terms of a diagnostic absorption model and compared with
experimental results. The differences observed between ideal and experimental results
help to validate the influence of components performances on the overall performance
of the facility.
An extension of the characteristic equation method, based on the characteristic
temperature difference to adiabatic absorption chillers, has been developed and applied
considering the facility features. Evaporator limitations have been included in the
analysis. The agreement between experimental data and the extended characteristic
equation is discussed, showing a good predictive capability, even at off-design
operating conditions.
The performances of two types of absorbers (liquid sheets and droplets as solution
spreading mechanisms in the absorber) have been characterized in terms of heat and
mass transfer. The liquid sheet configuration has shown better evaluation parameters
than droplets configuration.
Single and two phase heat transfer and pressure drop in a plate heat exchanger
operating as generator, has been analyzed. For the cases of subcooler and solution heat
exchanger, single phase heat transfer data has been obtained. The corresponding results
are analysed for each case and correlations equations have been obtained and compared
with those reported in literature.
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Keywords
Transmisión de calor, Dinámica de fluidos, Recursos energéticos