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Ignition within gas burner ejectors can lead to off design conditions and has significant influence on the burner behavior. Thus ignition in the ejector should be prevented. In the present study the influence of combustion reactions on the performance of gas burner injectors is investigated. To investigate if ignition is possible, simulated ignition delay times, using a detailed reaction mechanism, are compared to predicted mean residence times of the gas in the ejector. Gas burner ejectors are designed using one dimensional analytic equations, based on energy and momentum conservation equations and conventional isentropic equations. 1D results are compared to 2D computational fluid dynamics (CFD) simulations, to take into account non-ideal mixing effects along the ejector. Results are validated with experiments with air at room temperature. 1D results show very good agreement not only with CFD simulations for the case of non-reactive flows, but also with performed experiments. It is shown that the assumption of ideal mixing along the ejector and thus the comparison of the ignition delay time to the gas mean residence time, to predict ignition in the ejector, is not valid. Ignition in the ejector is possible, even if the ignition delay time is more than thirty times higher than the mean residence time. In addition to that, it is shown, that ignition and the choice of reaction mechanism have significant influence on the predicted gas burner ejector performance. Thus, the accurate prediction of ignition delay time and the use of a detailed reaction kinetic are mandatory to correctly predict the burner ejector behavior.

The Constant Rate of Momentum Change (CRMC) criterion attempts to improve the design of supersonic ejectors, that can be used in heat-powered chillers for industrial or air-conditioning use. Moving from its original formulation, the CRMC design method can be advanced accounting for friction irreversibilities and real gas behaviour, as done in a previous work by our research group. Here we present an upgraded version of this analysis, supported by experimental data from a prototype chiller using R245fa as working fluid. The analysis is extended to other fluids (water, isobutane, 5 HFCs and 3 HFOs) whose performance is calculated on a wide range of heat source/sink temperatures. The existing literature, based generally on ideal gas simulations, suggests that water yields poor results in terms of COP. This paper shows that this result may be argued. Low GWP fluid HFO1233zd also gives good results.

Reaction crystallization of struvite from water solutions containing 1.0 mass % of phosphate(V) ions by means of magnesium and ammonium ions action was investigated experimentally. The process was carried out in a DTM type crystallizer with liquid type jet pump in temperature 298K assuming stoichiometric conditions. Struvite crystals of mean size Lm from 4 to 22.4μm were produced depending on pH (pH from 9 to 11) and mean residence time of suspension in a crystallizer vessel (τ from 900 to 3600 s). In such process conditions linear growth rate of struvite crystals, calculated with SIG MSMPR kinetic model, decreases 2-time with the increase in pH level and 3-time with the elongation of mean residence time of suspension in a crystallizer, namely from 7.15 x 10–9 m/s (pH 9, τ 900 s) to 1.16 x 10–9 m/s (pH 11, τ 3600 s). Nucleation rate changed within the 9.3 x 108 – 9.0 x 109 1/(sm3) range. Crystal product of the best formed crystals, which maximal sizes reached 90μm while content of crystals of sizes below 3μm was ca. 12%, corresponded to pH 9 and mean residence time of suspension in a crystallizer 3600 s.

With ever-increasing population and rapid growth of industrialization, there is a great demand for fresh water, especially for drinking, as natural resources are becoming limited. In view of the above, different desalination technologies are evolving with a thrust for utilization of renewable energy sources like solar energy, ocean thermal energy, geothermal energy and waste heat. Vacuum desalination is one such technology in which fresh water is produced from brackish water by evaporation and subsequent condensation. This desalination technique involves different processes like pressurization of brackish water by a pump, creation and maintenance of a vacuum using jet pumps, and evaporation of brackish water at reduced pressure using waste heat from a power plant such as water from condenser. In this paper an analysis of a vacuum desalination system is presented. By applying the mass, momentum and energy balances across the various components, the governing equations are obtained for the analysis. These equations are solved using simulation. Validation of the simulated performance is made with the experimental data available in the literature. The study was carried out by varying operational parameters such as evaporator temperature, condenser temperature, evaporator flow rate, condenser flow rate and chamber pressure. Yield of fresh water obtained from the system increased as condenser temperature decreased and the evaporator temperature increased. Further, the yield increased as chamber pressure decreased. ? 2005 Elsevier B.V. All rights reserved.