The optimum geometries of the ejectors, which give maximum efficiency, are numerically predicted and experimentally measured. The numerical investigation is based on flow equations governing turbulent, compressible, two-dimensional, steady, time averaged, and boundary layer equations. These equations are iteratively solved using finite-difference method under the conditions of different flow regimes, which can be divided into several distinctive regions where the methods for estimating the mixing length are different for each flow region. The first region depicts the wall boundary layer, jet shear layer, and secondary and primary potential flows. The second one contains a single region of developing flow. A simple ejector with convergent-divergent primary nozzle was fabricated and experimentally tested. The present theoretical and experimental results are well compared with published data. The results obtained are used to correlate the optimum ejector geometry, pressure ratio, and ejector optimum efficiency as functions of the operation parameters and ejector area ratio. The resultant correlations help us to select the optimum ejector geometry and its corresponding maximum efficiency for particular operating conditions.

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The investment of solar energy in life applications has become mandatory to maintain a clean environment and reduce the use of fossil fuels. This work aimed to improve the performance of solar air heater (SAH) by using evacuated tube solar collectors ETSC integrated with nano-enhancer phase change material (NE-PCM). To achieve this purpose, a system consisting of 5 linked collecting panels was designed, fabricated, and experimentally investigated. Each panel included a glass-evacuated tube with two concentric aluminum pipes installed inside. NE-PCM was placed between the inlet and outlet air paths inside the evacuated tube to enhance the heat transfer rate. The performance was investigated with and without NE-PCM at five mass flow rates (0.006, 0.008, 0.01, 0.03, and 0.05 kg/s). Experimental results revealed that the highest temperature was 116, 108, 102, 95, and 93 °C, respectively, for the above mass flow rates without adding NE-PCM. The outlet temperature was decreased by 6–15 °C when using NE-PCM. The SAH efficiency was increased by 29.62% compared to the system without NE-PCM at 0.05 kg/s. The maximum thermal efficiency for the system with NE-PCM was 62.66% at 0.05 kg/s, and the pressure drop was 6.79 kPa under the same conditions. As well known, the hot air is used for a variety of purposes including space heating, food processing, drying of fruit, vegetables, dairy, and solar cooking.

The investment of solar energy in life applications has become mandatory in order to maintain a clean environment and reduce the use of fossil fuel. In this work, the performance of solar air heater is aimed to be improved with the help of evacuated tube solar collectors. To achieve this purpose, a system consisting of 5 linked collecting panels was designed, fabricated, and experimentally tested. Each panel included a glass-evacuated tube with two concentric aluminum tube installed inside. The system was reinforce by adding paraffin wax as a PCM and boosting its thermal conductivity by incorporating it with copper oxide nanoparticles CuO. The performance was investigated with and without Nano enhancer phase change material NE-PCM at five mass flow rates (0.006-0.008-0.05-0.03-0.01 kg/s). Experimental results revaluated that the highest temperature was recorded as 116°C at a mass flow rate of 0.006 kg/s. The maximum thermal efficiency with storage material was 38% at 0.05 kg/s, and the pressure drop was about 2.2kPa.

Tube bandles are widely used in heat exchangers for energy carriers and cooling product process, as a cooler for compressor in gas turbine unit and refrigeration plants. Heat transfer and pressure drop of isolated two-pass tube banks bandles with baffles at different locations are experimentally studied. In the present study, five heated test tubes are located at inlet of the first pass. The test tubes are heated at different rates (Q). The measurements are taken for the five test tubes. The length of the baffles and its location are taken into account. Also the effect of the tube banks aspect ratio is studied. From the measurements the local heat transfer coefficient and pressure drop are calculated. All the measurements are conducted at low Reynolds numbers range, (Re = 1000 to 3500).