No description available.

No description available.

No description available.

Solar thermal driven or assisted absorption cooling machines are gaining increasing importance due to the continually growing demand for airconditioning in domestic housing as well as office and hotel buildings. Presently there are no thermally driven absorption cooling machines available on the market that can provide a smaller cooling capacity than 10kW for cooling buildings. For this reason, two single-effect solar heated ammonia/water (NHJlH20) Diffusion-Absorption Cooling Machines (DACM) with a design cooling capacity of 2.SkW at evaporator temperatures between -10°C and +soC were designed, built and operated. The indirectly heated, solar powered generator (bubble pump) is the main new feature of this cooling machine. Data acquisition was conducted under laboratory conditions as well as under simulated field conditions for vacuum-tube collectors. The first pilot plant showed that coefficient of performance values (COP) range from 0.1 to 0.2 and the evaporator cooling capacity of the pilot plant could reach 1.SkW, but that the operation stability was insufficient. The second optimised and compacted pilot plant showed stable and continuous temperature and pressure levels. The reached COPs were between 0.2 and O.S and the continuous cooling performance between 1.0kW and 1.6kW. A maximum cooling performance of 2.0kW could be reached if the evaporator temperature was set to the relatively high value of 2SoC. The Diffusion-Absorption Cycle has been modelled using the constant characteristic equation of sorption chillers. An expanded, steady-state model which includes additional specific components of the DACM was developed based on the exact solution of the internal mass and energy balances of each component as well as the heat transfer between external and internal temperature levels. The internal enthalpies are calculated at each time interval using the simulation environment INSEL. The compared experimental and simulated data showed a good accordance.

Louvered-fin heat exchangers are used in the refrigeration systems of internal combustion engines (radiators) to dissipate the waste energy produced. Nevertheless, several authors state that this type of geometry can be applied with success to HVAC systems, since they are lightweight, compact, and capable of high heat fluxes without disproportional increase of the flow resistance. In this study, it is intended to extend the range of flow velocities and fluid temperatures generally studied in order to achieve results that could be applied in the design of louvered-fin heat exchangers applicable to HVAC systems. Louver-fin heat exchangers can exhibit several geometrical configurations. They can have round or flat tubes, splitter plates, triangular channels, rectangular channels, etc. Some of them can be considered as approximately two-dimensional as the louver plate fin and the corrugated louver-fin with rectangular channels (with or without splitter plate). The present study was directed towards the two-dimensional situation and heat transfer and pressure drop were quantified. In the first step performed, the parameters with possible influence were identified and ranges of use were chosen. Influence of the mesh size on the values of numerical results was quantified using the Richardson extrapolation methodology and the viability of its application to extrapolation in the case of unstructured grids was verified. Results of the mesh size study were applied to all subsequent numerical models in order to have grid independent results. A Parametric study using the Plackett-Burman design to identify the parameters of influence in the heat transfer and pressure drop was performed and correlations were determined having for base a Box- Behnken design. Finally a comparison with experimental results to validate numerical models was conducted. An attempt to construct a three-dimensional model was made and the results were presented and discussed.

No description available.

No description available.

No description available.