A three phase mathematical model of simultaneous heat and mass transfer of a batch operation for a fluidized bed is presented. The three phases are a solid free bubble, emulsion and solid phases. The model employs an elaborate five equations porosity model. Various correlations for the minimum fluidization parameters are surveyed and compared with the adequate one is being adopted in the model. The governing equations together with the boundary and initial conditions are presented for a cyclic operation of the bed. These are numerically solved for a test case where the bed is charged with silica gel particles to dehumidify a process air stream. Thus the bed works in an air dehumidification mode/bed regeneration mode cyclic operation with matching conditions.Results for the bed operation are presented as the temperature and humidity ratio variations for the test case. The results indicate the ability of the developed model to provide the␣required data for the concerned batch operated fluidized bed.

A thermodynamic analysis based on the first and second laws is conducted to evaluate the performance of a thermal vapor compression (TVC) desalination system. The performance of the analytical model is compared with operational data obtained from tests performed on a four-effect, low temperature TVC desalination system with performance ratios of 6.5–6.8, located in the U.A.E. The effect of the process variables on the plant's performance ratios is investigated. The exergy losses due to irreversibilities in different subsystems of the TVC system are evaluated and compared with those of the conventional multi-effect boiling (MEB) and mechanical vapor compression (MVC) desalination systems. The TVC system yields the least exergy destruction among the three systems. Subsystem exergy analysis shows that most of the exergy destruction in the TVC system occurs in the first effect and in the thermo-compressor. Overall exergy losses can be significantly reduced by increasing the number of effects and the thermo-compressor entrainment ratio, and by decreasing the top brine and heating steam temperatures.

This work presents a diesel engine total energy scheme where waste energy in the exhaust and block cooling water is recovered. The engine drives a RO plant, VC-A/C plant and supplies the neighbouring region electric power demands. The recovered energy fires an A/C system comprises a LiBr-H2O absorption machine and a silica gel air dehumidifying unit. The RO reject provides about one third of the cooling water required for various components in the scheme. Governing equations for the hot water regenerated air dehumidifying bed are presented, and the system is applied to a case study of 44/31 °C DBT/WBT. Results show the characteristics variations for the handled air as well as for the desiccant bed in both DH and RG mode in a coupled fashion with purging allowance. The hot cooling water regenerated desiccant bed showed a COPd of 0.62 and the exhaust gas driven absorption machine acquires a COPab of 0.8. The waste energy fired system could satisfy 40% of the A/C load at COPov of 1.15. The analysis showed an annual potential savings of 0.5×106 $ with an equivalent fuel savings of 11 000 barrel per year. The scheme saves 15.5% of the diesel capital plus a comparable percentage of the annual running expenses.

An experimental investigation is carried out to study the effect of a slot (t) jet injection onto the main stream parallel to a flate surface. Test runs covered a blowing ratio (M) of 1.5 to 4.2 for injection angle (α) of 30° and 60° to the downstream direction (x). Mean velocity (u) profiles are obtained forx/t up to 113 andy/t up to 40. Measurements are realized using a traversed fine double total head probe in a low speed wind tunnel.

In this paper, the differential equations governing the ionic flux, current intensity and potential drop for an electrodialysis (ED) unit are derived in terms of ionic concentration, ionic diffusion coefficient in both water and membranes, ionic electric transfer numbers and membrane properties. These equations are solved to obtain the unit potential difference together with the ionic flux of counter and co-ions through the membranes. The power required for the unit is obtained by multiplying the potential drop by the integral of the current intensity along the flow passage. The minimum power required is calculated and compared with an approximate analysis for the ED unit at different working conditions. The ratio between minimum power and approximate power ranges from 62-46 percent at Cfof2000 ppm to 26-19 percent at Cfof 10000 ppm by using compartment thickness of 0.5-1 mm, respectively.

This article presents a combined absorption-desiccant high performance airconditioning system suitable for hot humid areas. A LiBr-H2O absorption machine is powered by medium concentrators with a collection temperature of 140°C. The heat released in the absorption system condenser at 75°C is used for firing a silica gel (desiccant) dehumidifier. This consists of 2 silica gel beds of the cross flow type working alternatively in series with the absorption machine one bed at a time.

A numerical study of steam condensation over horizontal fluted tubes is presented. Condensate is driven by surface tension to the groove valley where it is drained by gravity.

This article demonstrates, through a thermodynamic analysis, the advantages of applying the Brayton cycle instead of the widely used Rankine cycle in a solar power generating unit. This is coupled to a vapour compression water chiller with a total cooling capacity of 65 ton refrigeration. Present work shows the benefits of combining solar, desalination, power and cooling disciplines to obtain a reasonably cheap solar cooling system. Hot water leaves a flat plate collector/storage loop at 95°C and is introduced into a flashing chamber. In the Brayton cycle, the generated vapour from the chamber is compressed, heated in a regenerator using turbine exhaust steam and passes to a fuel-fired superheater. The superheated steam at 120 kPa, 400°C expands in a steam turbine coupled directly to the vapour compressor. The net shaft power output drives a separate vapour compression cooling unit. In this theoretical cycle the nonsolar input energy represents 16% of the system total energy requirements with a basic power cycle efficiency of 15.7%. The overall coefficient of performance of this system is comparable to that of a sophisticated, pressurized solar cooling system with suntracking parabolic troughs. Comparison with the fuel-assisted solar steam Rankine power cycle shows that the present cycle requires 21% less fuel per unit power produced, with a 30% reduction in the superheater volume required, and requires 16% instead of 22% nonsolar energy.

An analysis of a combined reverse osmosis (RO) and a mechanical vapour compression (VC) desalination system suitable for remote areas or small communities is presented. This system consists of an RO unit with a recovery ratio of 25% and is driven by a diesel engine which is also coupled to the VC, and has a total output of 705 m2/d. Vapour discharged from the VC is superheated using a portion of the waste heat from the exhaust of the diesel engine. The degree of superheating is converted, in a desuperheater, into a 12% mass increase of saturated vapour at 112°C. This is introduced to a 3-effect VTE unit with the third effect working at atmospheric pressure and is connected to the suction side of the VC. Eleven flashing chambers are used for feed heating with a bottom temperature of 56°C. The pretreated RO brine, at high pressure, is used to cool the diesel engine. Then it is heated further, using both distillate and blowdown effluent from the bottom stage of the VTE feed heaters.

This article presents a thermodynamic analysis for a proposed hybrid system suitable for producing power or fresh water for small communities. The system includes a power generation loop and a desalination loop. These loops can work separately to produce power or combined to produce fresh water. The power loop comprises a solar pond, flashing chamber, vapour compressor VCI, steam superheater, steam turbine and a steam condenser. The desalination loop includes a vapour compressor VCII, vertical tube evaporator unit, multi stag flash feed heater and a heat rejection steam condenser. Hot water from the pond (97°C) is introduced into the flashing chamber and the generated steam is compressed to 125 kPa. Then the steam is superheated (using fuel) to a temperature of 315°C and is allowed to expand in a low pressure steam turbine exhausting into a condenser at 10 kPa. The turbine & VCI are mounted on the same shaft and the balance in the power generated can be used either as shaft power available or specifically for driving a desalination loop. This could be either a reverse osmosis RO or a vapour compression system. However, the analysis showed that the second one is more efficient than the RO. The VCII, driven by the turbine, is working across a 3-VTE multi effect unit associated with a 13-stage MSF feed heater coupled with an end condenser at 10kPa. Calculations showed that the power loop of a 100 m × 100 m solar pond assisted by 13 percent of its heat requirements, using fossil fuel, can generate 70 kW shaft power with a basic efficiency of 15%. When this loop is combined with a VC/VTE-MED unit a 200 t/day of fresh water can be produced at a PR of 9.4 and a thermal energy consumption (fuel) of 31 kJ/kg water produced which is less than any other system including the RO.