The present paper discusses gas turbine operating ranges of values of controlling cycle parameters for maximum first law efficiency , second law efficiency II, and work output wnet. Three cycles have been studied: simple cycle, recuperative cycle and general open cycle. Correlation equations relating maximum values of I, II and wnet to controlling parameters (compressor and turbine efficiencies, maximum cycle temperature, isentropic temperature ratio, fuel/air ratio, heat exchanger effectiveness and pressure drops in combustion chamber and heat exchanger) have been determined and discussed. The present paper reveals that cycle performance parameters I , II and wnet…. drastically depend on cycle controlling parameters. There is no narrow region of values of controlling parameters that produce concurrent maximum values of I , II and wnet . The maximum cycle temperature for the three cycles considered has a linear effect on I. , while other controlling parameters have nonlinear effects on I , II and wnet. For the general open cycle, the pressure drops Pcc and Pex have equal decreasing effects on I , II and wnet., while, both the fuel/air ratio f and heat exchanger effectiveness X have equal increasing effect on these performance parameters. The present correlation equations, augmented with other experimental and detailed design studies for each of the cycle units could provide good basis for the realistic design process of actual turbines.

The present work deals with one of the new techniques of saline water desalination. It is based on the humidification of ambient air and then dehumidification of this humid air to produce fresh water. Solar ponds as a source of hot saline water are well adapted for coupling with the unit. A computer programs were designed to investigate the performance characteristics at different operating conditions. The important design descriptions and the operating parameters of such units are identified. The effects of the operating parameters on the unit performance characteristics are studied. The productivities obtained from simple and modified models are qualitatively compared with the experimental values. Due to the simplicity of this technique, it may be a good candidate and is recommended if one looks for a solution for fresh water needs of small communities living in rural areas.

Analysis of heat transfer and fluid flow thermodynamic irreversibilities is realized on an example of a counter flow double pipe heat exchanger utilizing turbulent air flow as a working fluid. During the process of mathematical model creation and for different working and constructing limitations, total thermodynamic irreversibility is studied. The present work proves that the irreversibility is occurred due to unequal capacity flow rates (flow imbalance irreversibility). It is concluded that the heat exchanger should be operated at effectiveness greater than 0.5 and the best design will be achieved when  approach from one where low irreversibility is expected. A new equation is adopted to express the entropy generation numbers for imbalanced heat exchangers of similar design with smallest deviation from the exact value. The results obtained from the new equation are compared with the exact values and with that obtained by another author

The present paper studies the general characteristics and evaluates the optimum performance of a simple two-stage compression partial oxidation gas turbine (POGT) cycle that has been combined with a Rankine cycle. The controlling parameters of the combined cycle hat give optimum performance are determined and fitted into functional correlation equations. The values of the first-law efficiency and the second-law efficiency (èI and èII, respectively) for the mbined cycle are compared with those obtained for single POGT cycles. The effects of irreversibilities of the different units of the cycles are considered in the study. The combination of a POGT cycle with the Rankine cycle has achieved a maximum enhancement in net work output of 28.76% and optimum values of èI  58% and èII  80%. The present findings can form a very important basis for a complete phenomenological design of a combined POGT/Rankine cycle to achieve optimum performance