Abstract
In this work, the performance of a single effect absorption cooling system fed by solar thermal energy is evaluated. The absorption chiller includes a membrane-based microchannel desorber using three types of nanoparticles: Al2O3, CuO, or carbon nanotubes (CNT). Correlations available in the open literature to calculate the thermal conductivity of nanofluids are reviewed. Using experimental data for the water-lithium bromide solution (H2O-LiBr) with Al2O3 and CNT nanoparticles, the most appropriate correlation for thermal conductivity is selected. Nanofluid properties are evaluated using a concentration of nanoparticles of up to 5% in volume. The largest increase in the desorption rate (7.9%), with respect to using pure H2O-LiBr solution, is obtained using CNT nanoparticles and the maximum concentration of nanoparticles simulated. The performance of the chiller is evaluated and the daily solar coefficient of performance (SCOP) for the solar cooling facility is obtained. The best improvement with respect to the conventional system (without nanoparticles) represents an increase in the cooling effect of up to 6%. The maximum number of desorber modules recommended, always lower than 50, has been identified.
Highlights
Absorption cooling chillers can be fed by any heat source, including renewable or waste heat, for example, from solar thermal collectors
Regarding the H2 O-LiBr-carbon nanotubes (CNT) nanofluid, Figure 5 includes a comparison of the values obtained
Regarding the H2O-LiBr-CNT nanofluid, Figure 5 includes a comparison of the values obtained using the different correlations
Summary
Absorption cooling chillers can be fed by any heat source, including renewable or waste heat, for example, from solar thermal collectors. The authors of [15] evaluated an intermittent air gap membrane distillation technology and the water-Carrol and H2O-LiBr working pairs In this absorption arrangement employing a porous membrane in a desorber-condenser fed with solar thermal case, the use of this technology provides promising results. A simple model of a was developed and validated by [21], while a parametric study evaluating the effect of operating and design variables can be found in [22] Another way to reduce the volume of absorption chillers is increasing the mass and heat transfer rates by adding nanoparticles to the solution. The previous literature review shows the increased interest in improving the performance of desorbers used in absorption cooling chiller in two ways: using membrane-based components and adding nanoparticles to the base solution. The performance of a single effect solar absorption cooling system incorporating the membrane-based desorber, H2 O-LiBr nanoparticles in the absorption chiller, and a flat plate thermal collector is evaluated
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