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From 2010 to 2015, three similarly design based absorption chillers have been developed, manufactured and characterized on test benches. The chillers are all ammonia-water thermally driven single effect chiller. They are intended to operate using directly solar thermal energy or using waste heat from Concentrated Solar Plant (CSP). The first one is a laboratory prototype, fully instrumented with a cooling capacity of 5 kW. The second one is a pre-industrial version of the first prototype with the same cooling capacity but less instrumented and with a compact design. The last development is a 100 kW cooling capacity chiller, with technical choices between the two first prototypes, but design to provide cooling effect at temperatures suitable from air-conditioning to ice making. In this paper, the design principles and the technological choices made for each chiller are described and a comparison of the experimental results is done.

International audience; 7 HIGHLIGHTS 8 • A commercial absorption chiller has been tested in dynamic operating conditions on a semi-virtual test bench. 9 • The absorption chiller was modelled in a dynamic way using artificial neural networks. 10 • The model is validated using experimental data. 11 • The neural model predictions are very satisfactory, absolute relative errors of the transferred energy are in 0.1-12 6.6%. 13 ABSTRACT 14 Thermally driven chillers powered by waste-heat or solar energy such as absorption chillers could be more 15 appropriate than commercial air-conditioners that use electricity-powered compression cycles. The more the latter 16 are installed in cities the more heat is released and thus the outdoor temperature increases. As a consequence, 17 performance efficiency of the systems based on compression cycles will reduce. In this case those systems will 18 consume a big deal of electricity. However, absorption chillers still face a big impediment to their commercial 19 development for small capacity installations in buildings. The aim of this paper is to present a methodology to model 20 and evaluate the energy performance of such systems so that users could have reliable information about the long-21 term performance of their systems in the wanted boundary conditions before the installation of the product. 22 Absorption chillers behavior could be very complex and unpredictable especially when the boundary conditions are 23 variable. The system dynamic must be then included in the model. Artificial neural networks (ANNs) have proved to 24 be suitable to tackle such complex problems, particularly when the physical phenomena inside the system are 25 difficult to be modelled. Reliable "black box" ANN modelling is able to identify global models of the system without 26 any advanced knowledge of its internal operating principles. The knowledge of the system's global inputs and 27 outputs is sufficient. The proposed methodology was applied to evaluate a commercial absorption chiller. Predictions 28 of the ANN model developed were compared, with a satisfactory degree of precision, to two days of experimental 29 measures. The neural model predictions are very satisfactory, absolute relative errors of the transferred energy are in 30 0.1-6.6%. 31 KEYWORDS 32

International audience; In this paper,experimental and numerical studies of heat and mass transfer in a falling film absorber are presented. The investigated absorber is a plate heat exchanger used ina falling film configuration. The ammonia-water solution flows in a falling film mode along the plates. The vapour flows co-current with the falling film and the coolant fluid is in a counter-current flow with the falling film. A prototype of ammonia-water absorption chiller isused to experimentally study the absorber behaviour in real operating conditions. Amacro study of the absorber and a local analysis deduced from local temperatures measurements along the falling film are presented. A numerical model and a simulation tool aredeveloped in order to complete the experimental investigations.The associatednumerical parametric studyaims to separatethe coolant mass flow rate impact.The model is validated with experimental dataand a maximal relative error of 15 % is observedbetween experimental and numerical results. The results of this study suggest that during the absorption process,mass transfers are controlled by the falling film mass transfer resistance and that the liquid-side heat transfer resistance is negligible.

This paper presents a numerical and experimental study of absorption phenomenon in ammonia-water absorption chiller which is a very promising technology in the solar cooling field. The purpose of the research is to analyse the coupled heat and mass transfers that take place in a plate heat exchanger used as absorber in order to identify limiting transfers. For this purpose, a numerical modeling of a falling film absorber has been performed. Then, an experimental study has been carried out on a test bench in order to experiment the absorber in real operating conditions and to validate the numerical model. So, experimental and numerical results are compared to discuss hypothesis of the model and analyse the global behaviour of the absorber. Moreover, local phenomena are discussed thanks to the numerical study.

The development of a small capacity absorption chiller and the numerical and experimental results are presented in this paper. The prototype is a thermally driven ammonia-water absorption chiller of 5 kW cooling capacity for solar cooling applications. The chiller was developed in an industrial perspective with a goal of overall compactness and using commercially available components. In order to characterize various component technologies and different optimization components, the prototype is monitored with temperature, pressure and mass flow rate accurate sensors. The resulting chiller, characterized by a reduced load in ammonia-water solution and the use of brazed plate heat exchanger, has shown good performance during the preliminary tests. A comparison with the expected numerical results is given.

In this paper, a general mathematical model for the dynamic simulation of a single-effect LiBr/water absorption chiller is presented. The model is based on mass and energy balances applied to the internal components of the machine, and it accounts for the non-steady behaviour due to thermal and mass storage in the components. The validation of the mathematical model is performed through experimental data collected on a commercial small-capacity water-cooled unit. Due to the peculiar technology adopted in the real chiller, a special effort was made to identify the appropriate values of the main physical parameters. The validation of the model is based on the values of the water temperature at the outlet of the machine, as no measurement inside the machine was possible; anyway, a consistency analysis applied to the internal parameters is also presented. The agreement between experimental and simulated results is very good, both on a daily and on a seasonal basis.

International audience; Six solar-powered air-conditioners, based on four principles (LiBr + H2O liquid sorption, silicagel + water solid sorption, BaCl2 + NH3 thermochemical reaction, and desiccant + humid air open cycles) have been operated in five places (from the low-altitude Alps to a tropical island including Mediterranean Sea shore). A common experimentation procedure was applied over months, except for some cases, and during several years. Data were recorded, gathered, and analyzed similarly for the six units. Is established a sound framework based on relevant quantities, some non-dimensional and others dimensional but referred to relevant scales, with the purpose that direct comparison of results is sensible. Similarly, are defined the sub-units to be considered for further analysis. This framework is applied to (i) data averaged over long periods, and (ii) data obtained on one single day with given insolation. Comprehension obtained from comparison in that framework gives access to notions as different as (i) fundamental differences between systems, (ii) aging of components, and (iii) non-linearity of the basic operation of such solar-powered units. The theoretical analysis of this non-linearity is developed. The framework established in this article could thus be used for comparing other solar-powered processes.

6 p.; International audience; This work was done in the SOLERA project (http://www.solera-project.eu), Sixth EU Framework Program (FP6), co-funded by EC and coordinated by Fraunhofer ISE. It started in November 2007 and will stop in November 2011. The goal of the project SOLERA is to install, operate and evaluate three different solar cooling systems of different sizes.