Hybrid nanofluid is the new generation of heat transfer fluid for various heat transfer applications where transport characteristics are substantially higher than the base liquid. The study presents an experimental investigation of rheological and thermophysical properties of Al2O3/ CuO hybrid nanoparticles suspended in 25:75 (by weight) ethylene glycol and water mixture. This manuscript presents experimental work of thermophysical properties of Al2O3/CuO/water/ethylene glycol hybrid nanofluids and its effect on thermal efficiency of flat plate solar collector. Nanofluids of particle volume percentage of 0.5%, 1%, 1.5% and 2% were tested. Results show that thermal conductivity, viscosity and density increases with nanoparticles concentration. The efficiency of the collector was improved by 45% by increasing the nanoparticle weight fraction.

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This study examines the possibility for enhancing the use of stone cutting sludge waste in the production of building bricks and terrazzo tiles, which would reduce both the environmental impact and the production costs. Stone cutting wastes in the form of sludge is currently generated at several factories in Jordan. At the Samara factory, incorporation of the sludge in the batch formulations of bricks and terrazzo tiles was examined. The physicochemical and mineralogical characteristics of the sludge were analyzed to identify the major components. Results indicated that the sludge generated from stone cutting could be used in producing concrete bricks. Mixtures of aggregates with added amounts of sludge were used successfully to produce non-load bearing bricks. Sludge was also used to produce terrazzo tiles and the results indicate that the transverse strength, water absorption and tile measurements, for all the taken samples, comply with Jordanian standards. The transverse strength decreased while water absorption increased as the sludge ratio increased.

The validity of the local thermal equilibrium assumption in the periodic free convection channel flow is investigated analytically. Two cases are considered where in the first case transverse conduction in the solid domain is included while in the second case transverse conduction in the fluid domain is included. The periodic disturbance in the free convection flow is due to a periodic thermal disturbance imposed on the channel walls. The DarcyBrinkman model is used to model the flow inside the porous domain. It is found that four dimensionless parameters control the local thermal equilibrium assumption in the first case and five parameters control the local equilibrium assumption in the second case. The criteria that secure the validity of the local thermal equilibrium assumption are derived.

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