Rotating-drum solar still with enhanced evaporation and condensation techniques: Comprehensive study

Rotating-drum solar still with enhanced evaporation and condensation techniques: Comprehensive study
In this study, the thermal performance of the solar still was aimed to be improved in successive stages. This improvement was achieved via using a rotating drum inside the basin still to be nominated as drum distiller. The drum helps to increase the evaporative surface area and decrease the thickness of the saline water film. In the next stage of experimentations, a solar water heater was integrated into the drum distiller. After that, an external condenser was incorporated with drum still. Then, in the last stage of experiments, the effect of copper oxide nanoparticles on the performance of drum distiller was investigated. Different rotational speeds such as 0.02, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 rpm were investigated. A theoretical model was built to predict the performance of the distillers under different conditions. An acceptable agreement was noticed between the experimental and theoretical values (7–13%). Results revealed that the maximum productivity was obtained at 0.1 rpm and using the condenser, heater, and nanofluid. Under these conditions, the freshwater productivity was 9220 L/m2 for the drum still compared to 2050 L/m2 for the conventional still with an enhancement percentage of 350%. Additionally, the estimated cost of 1 L of distillate for traditional and drum stills are about 0.05 and 0.039 $, respectively. ...

published in: 2020-06-09 00:30:12

Numerical modelling of hydrogen-natural gas mixtures flows in looped networks

Numerical modelling of hydrogen-natural gas mixtures flows in looped networks

This article concerns the numerical analysis of high pressure hydrogen-natural gas mixtures flows in pipeline networks during steady and transient states. The considered fluid is an homogeneous mixture of hydrogen and natural gas. An isentropic process is admitted for both components and under such assumption the density of the binary gas mixture is defined. The steady state was studied by the use of Hardy Cross method. The numerical simulation of the transient regime was performed by solving the conservation equations, for one-dimensional isentropic compressible flow, using the characteristics method of specified time intervals. The obtained results have proved the efficiency of the characteristics method compared to other numerical techniques. The numerical obtained results have shown that, during transients, pressure oscillations for hydrogen and hydrogen-natural gas mixtures are higher compared to those for natural gas.

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published in: 2020-03-08 11:41:25

Water-Hammer Control in an Actual Branched Cast Iron Network by Means of Polymeric Pipes

Water-Hammer Control in an Actual Branched Cast Iron Network by Means of Polymeric Pipes
The purpose of this paper is to numerically investigate the impact of replacing existing cast iron pipes of an actual branched network with High- Density Polyethylene HDPE pipes on damping and dispersing pressure waves created by water hammer phenomenon. A transient solver based on the Kelvin- Voigt formulations was developed. The numerical model takes into consideration the pipe wall viscoelastic behavior of polymeric pipes. The numerical resolution method of characteristics MOC with specified time intervals was adopted to solve the nonlinear, hyperbolic, partial differential equations that govern the unsteady flow generated in the network. The reliability of the numerical model was validated with experimental results from the literature. Flow disturbances in the branched network were generated due to the simultaneous fast closure of both downstream valves. Three different configurations of control strategies were suggested. The proposed strategies were based on implementing one or two high-density polyethylene (HDPE) pipes in the sensitive regions where the highest pressure perturbations took place. A comparison between the performances of the different control strategies was performed. Obtained results showed that even with one HDPE pipe implemented in the network, the positive and negative pressure peaks were reduced remarkable. Furthermore, the results have also shown that the risk of cavitation has been completely avoided using the control strategies. ...

published in: 2020-03-08 11:40:52

Investigation of viscoelastic effects on transient flow in a relatively long PE100 pipe.

Investigation of viscoelastic effects on transient flow in a relatively long PE100 pipe.
In this paper, the dynamic effect of the viscoelastic behavior of PE100 material, on the transient flow in a relatively long pipe, has been studied. At first, to study the transient flow in pipes with fluid structure interaction (FSI), two mathematical models, i.e., fully coupled four equation model and simplified two equation model, have been developed. The method of characteristics has been used to solve the model. Then, we have demonstrated that the viscoelastic behavior of PE100 plays a primordial role in the damping of the water hammer phenomenon. It has a dynamic effect to cause the decrease of pressure wave velocity with increase of pressure along the wave front. At the end of the paper, It has been shown that the coupled model with FSI does not introduce many changes from the simplified viscoelastic model. ...

published in: 2020-03-08 11:40:05