Optimizing the regeneration process parameters for forward osmosis to produce clean water at low temperature

One-fifth of the world will face sever water shortage by 2040 as climate change and a growing population pushes up demand. Recently, Qatar water resources are becoming strained and stressed as Qatar only gets seven inches of rain per year. Furthermore, World Resources Institute (WRI) ranked all the countries over the world according to the severity of water crisis and the Middle East was one of the worst regions. Nine countries were considered extremely susceptible and Qatar was ranked as a number 3, after Bahrain and Kuwait. While the country (Qatar) population is growing – as today, 2.5 million residents are forecast to multiply eightfold by 2050. Thermal processes produce more than 90% of desalinated water, where the desalination process is energy intensive, and affecting the environment. The scope of the present work is to develop a process to produce clean water at low operating conditions (temperature Please click Additional Files below to see the full abstract

Zeta Potential Optimization of Nano Chitason/SrCl2/MgO Suspension for Electrophoretic Deposition Using Taguchi Method

The stability of Electro Phoretic Deposition (EPD) suspensions containing nanoparticles relies on the impact of Zeta Potential (ZP or ). This property ensures that the nanoparticles have a consistent and stable surface charge, resulting in a uniform and stable coating. This research has been conducted as an experimental study and used the Taguchi method to design experiment optimization of the Zeta potential values, which were obtained by preparing nine suspensions. The study aimed to determine the optimal ZP value for the EPD suspension created with three materials mixed: nanochitason, Chitason/SrCl2/MgO, and a constant value of hydroxyapatite (HA) with consideration of the pH effect. After conducting an analysis, it was found that the suspension's Zeta Potential is negatively charged below a pH value of 8.22. Between 8.22 and 9.7, the ZP has a positive charge. The suspension's isoelectric point (IEP) is 8.22, with a high correlation coefficient indicating the model's reliability in predicting responses. The analysis showed that SrCl2 has the most significant impact on the suspension's ZP, followed by Chitason (CH), with MgO having the least impact. The results demonstrate the effectiveness of this analysis in determining the optimum ZP value for various solutions prepared from different biomaterial particle

Experimental and theoretical investigation of a three-phase direct contact condenser.

In the present work, for the first time, an experimental and theoretical study of the heat transfer characteristics of a bubble type three-phase direct contact condenser has been carried out. The experiments were conducted using a Perspex column of 70 cm in total height and 4 cm inner diameter, as a direct contact condenser. The active column height throughout the experiments was 48 cm. Pentane vapour at three different initial temperatures (40℃, 43.5℃ and 47.5℃), was used as the dispersed phase while tap water at a constant temperature (19℃) was used as the continuous phase. Seven different dispersed phase mass flow rates and five different continuous phase mass flow rates were tested. The experiments considered the transient temperature distribution along the direct contact condenser, the steady-state temperature distribution, the volumetric heat transfer coefficient, the heat transfer rate per unit volume and the holdup ratio. Also, the efficiency and capital cost of the direct contact condenser were estimated, and the heat transfer of the three-phase direct contact condenser during flooding was studied. Theoretical models describing the direct contact condenser were developed. These models included the transient temperature distribution, the steady-state temperature distribution and the volumetric heat transfer coefficient. These models implicitly involved new derivations for the surface heat transfer coefficient, the two-phase bubble size, the relative velocity of two-phase bubbles, the drag coefficient and the added mass of the two-phase bubble. All expressions were derived analytically except for the transient temperature distribution along the condenser which was found numerically, using MATLAB. The results showed that the mass flow rate ratio has a significant effect on the heat transfer characteristics of the condenser, while the initial temperature of the dispersed phase has only a slight effect. The models developed were fitted the experimental data well

Convective Heat Transfer Measurements in a Vapour-Liquid-Liquid Three-Phase Direct Contact Heat Exchanger

Energy usage is increasing around the world due to the continued development of technology, and population growth. Solar energy is a promising low-grade energy resource that can be harvested and utilised in different applications, such solar heater systems, which are used in both domestic and industrial settings. However, the implementation of an efficient energy conversion system or heat exchanger would enhance such low-grade energy processes. The direct contact heat exchanger could be the right choice due to its ability to efficiently transfer significant amounts of heat, simple design, and low cost. In this work, the heat transfer associated with the direct contact condensation of pentane vapour bubbles in a three-phase direct contact condenser is investigated experimentally. Such a condenser could be used in a cycle with a solar water heater and heat recovery systems. The experiments on the steady state operation of the three-phase direct contact condenser were carried out using a short Perspex tube of 70 cm in total height and an internal diameter of 4 cm. Only a height of 48 cm was active as the direct contact condenser. Pentane vapour, (the dispersed phase) with three different initial temperatures (40℃,43.5℃ and 47.5℃) was directly contacted with water (the continuous phase) at 19℃. The experimental results showed that the total heat transfer rate per unit volume along the direct contact condenser gradually decreased upon moving higher up the condenser. Additionally, the heat transfer rate increases with increasing mass flow rate ratio, but no significant effect on the heat transfer rate of varying the initial temperature of the dispersed phase was seen. Furthermore, both the outlet temperature of the continuous phase and the void fraction were positively correlated with the total heat transfer rate per unit volume, with no considerable effect of the initial temperature difference between the dispersed and continuous phases

Measuring the average volumetric heat transfer coefficient of a liquid–liquid–vapour direct contact heat exchanger

The average volumetric heat transfer coefficient in a spray column liquid–liquid–vapour direct contact evaporator has been experimentally investigated. The experiments were carried out utilising a cylindrical Perspex tube of diameter 10 cm and height and 150 cm. Saturated liquid n-pentane and warm water at 45 °C were used as the dispersed and continuous phases, respectively. Three different dispersed flow rates (10, 15 and 20 L/h) and four different continuous phase flow rates (10, 20, 30 and 40 L/h) were used in the study. The effect of different parameters, such as the initial drop size, continuous and dispersed phase flow rates and sparger configuration, on the average volumetric heat transfer coefficient in the evaporator was studied. The results showed that the average volumetric heat transfer coefficient was reduced as the initial drop size increased. Also, both the continuous phase and the dispersed phase flow rates have a significant positive impact on the average volumetric heat transfer coefficient

Heat transfer modelling of two-phase bubbles swarm condensing in three - phase direct - contact condenser

An analytical model for the convective heat transfer coefficient and the two-phase bubble size of a three-phase direct contact heat exchanger was developed. Until the present, there has only been a theoretical model available that deals with a single two-phase bubble and a bubble train condensation in an immiscible liquid. However, to understand the actual heat transfer process within the three-phase direct contact condenser, characteristic models are required. A quasi - steady energy equation in a spherical coordinate system with a potential flow assumption and a cell model configuration has been simplified and solved analytically. The convective heat transfer in terms of Nu number has been derived, and it was found to be a function to Pe number and a system void fraction. In addition, the two-phase bubble size relates to the system void fraction and has been developed by solving a simple energy balance equation and using the derived convective heat transfer coefficient expression. Furthermore, the model correlates well with previous experimental data and theoretical results

Direct contact evaporation of a single two-phase bubble in a flowing immiscible liquid medium. Part I: two-phase bubble size

The evaporation of a single n-pentane drop in another warm flowing liquid (water) medium has been studied experimentally. A Perspex column with an internal diameter of 10 cm and height of 150 cm was used throughout the experiments. N-pentane liquid at its saturation temperature and warm flowing water with flow rate of 10, 20, 30 and 40 L/h were employed as the dispersed and continuous phases, respectively. The active height of the continuous phase in the column (i.e. the level of the continuous phase in the column) covered only 100 cm of the column’s height. A Photron FASTCAM high-speed camera (~ 65,000 f/s) was used to film the evaporation of the drop, while AutoCAD was used to analyse the images from the camera. The diameter ratio (diameter of growing two-phase bubble to initial drop diameter) of the two-phase bubble formed because of the evaporation of the pentane drop in direct contact with the water was measured. Also, the vaporisation ratio (x), the open angle of vapour (β), the total height for complete evaporation and the total evaporation time were measured. The effects of the continuous phase flow rate and the temperature difference between the contacting phases, in terms of Jakob number (Ja), on the measured parameters were investigated. Furthermore, a statistical model to fit the experimental data was developed. The experimental results showed that the diameter of the two-phase bubble is strongly influenced by varying the continuous phase flow rate. The final size of the evaporated vapour bubble was unaffected by the flow rate of the continuous phase, while both the total height required for complete evaporation and hence the time required was significantly influenced. A similar impact was observed for the vaporisation ratio and the open angle of vapour

Numerical study on the effect of the location of the phase change material in a concentric double pipe latent heat thermal energy storage unit

Latent heat thermal energy storage (LHTS) represents an intriguing solution to the problem of variability of supply that exists in solar thermal power systems. One such storage system consists of a double pipe, where a phase change material (PCM) is enclosed in either the central pipe, or the annulus surrounding it. The heat transfer fluid fills the other void in the system. Whether the PCM is used in the central pipe or the annulus could, potentially, significantly alter the thermal performance of the system. Thus, a comparison between the PCM mounted in the annulus (case A) and the inner tube (case B) was conducted numerically, to investigate the advantages and disadvantages of each case with regard to the melting and solidification performance. A horizontal double pipe latent heat thermal energy storage device was considered. The numerical simulation solved the transient balance equations in a two-dimensional system. The enthalpy-porosity method was used to simulate the phase change and the Boussinesq approximation, which accounts for the small changes in density that drive natural convection, was applied. The effect of the initial temperature of the heat transfer surface (HTS) on the sensible and latent heat changes of the model PCM, RT-50, was tested for both the melting and solidification processes. Aiming to assess the differences in the storage performance, the average PCM temperature, the liquid fraction, and the average velocity of both the melting and solidification processes were examined. The results of the simulation showed that for both cases, convection was dominant after only a short period of the melting process. The melting time was significantly different in the two cases, i.e. it was shorter in case B than case A by almost 50%. Furthermore, an increase in the temperature of the HTS by 5 °C notably affected the melting time of both cases by as much as 20%. This effect was more pronounced in case B, which had a melting time which was 41% shorter than case A. Finally, the results revealed that the solidification process in case A was more rapid than case B with the total solidification time of case A being lower by 43.4%