Purpose The purpose of this paper is to investigate the heat transfer of laminar and turbulent pulsating Al203/water nanofluid flow in a two-dimensional channel. In the laminar flow range, with increasing Reynolds number (Re), the velocity gradient is increased. Also, the Nusselt number (Nu) is increased, which causes increase in the overall heat transfer rate. Additionally, in the change of flow regime from laminar to turbulent, average thermal flux and pulsation range are increased. Also, the effect of different percentage of Al2O3/water nanofluid is investigated. The results show that the addition of nanofluids improve thermal performance in channel, but the using of nanofluid causes a pressure drop in the channel. Design/methodology/approach The pulsatile flow and heat transfer in a two-dimensional channel were investigated. Findings The numerical results show that the Al2O3/Water nanofluid has a significant effect on the thermal properties of the different flows (laminar and turbulent) and the average thermal flux and pulsation ranges are increased in the change of flow regime from laminar to turbulent. Also, the addition of nanofluid improves thermal performance in channels. Originality/value The originality of this work lies in proposing a numerical analysis of heat transfer of pulsating Al2O3/Water nanofluid flow -with different percentages- in the two-dimensional channel while the flow regime change from laminar to turbulent.

Nowadays, the freshwater is one of the most critical issues for humans. In this regard, desalination systems can be beneficial. In this research, at first different types of desalination systems and their governing equations is studied. Then the energy consumption of evaporative vacuum easy desalination system with brine tank is modeled. This modeling and the equations governing the energy consumption of new subsets such as the evaporator, condenser, vacuum pump, and other pumps are presented. In the end, the economic modeling of the system is investigated. The feasibility of using the system is reported in three cities (Abu Dhabi, Las Palmas, and Perth). The results shown that the annual operating cost of the pumps is estimated to be 0.19 M€ yr −1 , 0.51 M€ yr −1 and 0.14 M€ yr −1 for Abu Dhabi and Las Palmas and Perth respectively. Also, the annual cost of fresh water production is compared with other reaches in these cities. The results are shown that Perth has the lowest cost of the fresh water output at 0.67 M€ yr −1 and Las Palmas has the highest cost of fresh water production with 0.104 M€ yr −1 . The reason is the difference in the electricity prices in these cities.

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In this research, the integrated carbon dioxide power cycle with a geothermal energy source to supply the required reverse osmosis desalination power for freshwater production is defined. It is also a carbon dioxide power cycle, coupled with thermal energy recovery of infrared energy of liquid natural gas (LNG) to generate more power. A sodium hypochlorite generator is considered to prevent the brine water discharging. The brine water portion of the desalination outlet was the input to this generator. The cycling power is consumed by the desalination system and sodium hypochlorite generator. After modeling, the advanced exergy analyses are studied. By exergy analysis, it is observed that in this model the condenser has the highest exergy destruction rate, equal to 952 kW. Additionally, the unavoidable part of the exergy destruction of carbon dioxide turbine constitutes 88% of its exergy destruction that is equal to 301 kW. So this component is the best option to improve exergy destruction.

In this research, the integrated carbon dioxide power cycle with the geothermal energy source to supply the required reverse osmosis desalination power for freshwater production is defined. The cycling power is consumed by the desalination system and sodium hypochlorite generator. Exergoeconomic analysis, and optimization are studied. Exergoeconomic analysis is shown that the desalination system, sodium hypochlorite generator, carbon dioxide turbine, and natural gas turbine have the highest rate for the sum of capital gain and exergy destruction cost. For the first case of optimization, the total cost rate is considered as the objective function. The optimal inlet discharge rate of sodium hypochlorite generator was 62% of the brine water outlet discharge rate of the desalination system. Plus, the total cost rate is reduced by 10% compared to the general case when 100% of brine water discharge rate of the desalination system enters into the sodium hypochlorite generator. The second case is multiobjective optimization to reduce costs and increase productivity.