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Abstract: A mathematical model for ammonia–water bubble absorbers was developed and compared with experimental data using a plate heat exchanger. The analysis was performed carrying out a sensitive study of selected operation parameters on the absorber thermal load and mass absorption flux. Regarding the experimental data, the values obtained for the solution heat transfer were in the range 0.51–1.21kWm−2 K−1 and those of the mass absorption flux in the range 2.5–5.0×10−3 kgm−2 s−1. The comparison between experimental and simulation results was acceptable being the maximum difference of 11.1% and 28.4% for the absorber thermal load and the mass absorption flux, respectively. [Copyright &y& Elsevier]

Automatic proportional integral derivative control techniques are applied in a single-stage solar absorption cooling system, showing 3.8 kW (~1 ton) cooling capacity, with a coefficient of performance of 0.6 and −4.1 °C evaporator cooling temperature. It is built with plate heat exchangers as main components, using ammonia–water as the working mixture fluid and solar collectors as the main source of hot water. Control tuning was verified with a dynamical simulation model for a solution regarding mass flow stability and temperature control in the solar absorption cooling system. The controller improved steady thermodynamic state and time response. According to experimental cooling temperatures, the system could work in ranges of refrigeration or air-conditioning end-uses, whose operation makes this control technique an attractive option to be implemented in the solar absorption cooling system. [ABSTRACT FROM AUTHOR]

The studies of ejector refrigeration systems employing refrigerant R134a for air conditioning are scarce and nonexistent for ice making when its potential application in developing countries will lessen their refrigeration needs. So, a parametric study for an ice making solar booster assisted ejector refrigeration system operating with R134a is carried out System energy and exergy efficiencies as well as ejector efficiency are presented as a function of generator and condenser temperatures and booster discharge pressure. A discussion on maximum ejector efficiency and its effect in system behavior is also carried out With results indicating that for an evaporator temperature of -1O° C, the system can operate at a generator temperature of 85°C with average energy efficiencies between 0.21 and 0.58, depending on the condenser temperature. Consequently, these systems could be a solution for solar refrigeration using off-the-shelf components. [ABSTRACT FROM AUTHOR]

Absorption systems are a sustainable solution as solar driven air conditioning devices in places with warm climatic conditions, however, the reliability of these systems must be improved. The absorbing component has a significant effect on the cycle performance, as this process is complex and needs efficient heat exchangers. This paper presents an experimental study of a bubble mode absorption in a plate heat exchanger (PHE)-type absorber with NH3-LiNO3 using a vapor distributor in order to increase the mass transfer at solar cooling operating conditions. The vapor distributor had a diameter of 0.005 m with five perforations distributed uniformly along the tube. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where the ammonia vapor was injected in a bubble mode into the solution in the central channel. The range of solution concentrations and mass flow rates of the dilute solution were from 35 to 50% weight and 11.69 to 35.46 × 10−3 kg·s−1, respectively. The mass flow rate of ammonia vapor was from 0.79 to 4.92 × 10−3 kg·s−1 and the mass flow rate of cooling water was fixed at 0.31 kg·s−1. The results achieved for the absorbed flux was 0.015 to 0.024 kg m−2·s−1 and the values obtained for the mass transfer coefficient were in the order of 0.036 to 0.059 m·s−1. The solution heat transfer coefficient values were obtained from 0.9 to 1.8 kW·m−2·K−1 under transition conditions and from 0.96 to 3.16 kW·m−2·K−1 at turbulent conditions. Nusselt number correlations were obtained based on experimental data during the absorption process with the NH3-LiNO3 working pair. [ABSTRACT FROM AUTHOR]

We have developed a simple model of a micro gas turbine system operating at high ambient temperatures and characterized its performance with a view to integrating this system with thermally activated cooling technologies. To develop and validate this model, we used experimental data from the micro gas turbine test facility of the CREVER research centre. The microturbine components were modelled and the thermodynamic properties of air and combustion gases were estimated using a commercial process simulator. Important information such as net output power, microturbine fuel consumption and exhaust gas mass flow rate can be obtained with the empirical correlations we have developed in this study. This information can be useful for design exhaust gas fired absorption chillers. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents the design criteria, methodology. and results of the basic and detailed engineering for a descending film ammonia absorber using air cooled finned tubes, which is part of an advanced absorption cooling system (solar generator absorber heat exchange cycle). The design consists in determining all the construction parameters for the air cooled ammonia absorption unit, starting with the operating conditions defined by a thermodynamical simulation of the process considering both physical and operational design restrictions. The chosen option was based on a comparison between the advantages and disadvantages of each possible array, type, and geometry. After performing the operational simulation, thermal and mechanical designs, and the consistency analysis, it was found that an absorption unit using 29 5/8 NPT 14 (BWG) steel carbon ASTM A-179 tubes, with pure SB-234 aluminum fins was the best option. The tubes are arranged in an equilateral triangle fashion, with crossed air flow cooling. [ABSTRACT FROM AUTHOR]