Investigation and Improvement of the Humidification–Dehumidification Solar Water Desalination System Implemented Wick as Packing Material

Theoretical and experimental study of a seawater desalination system based on humidification-dehumidification technique

Desalination by humidification dehumidification processes is a promising simple, cost effective and low maintenance concept. It works on the principle of air humidification at high temperature and dehumidification at relatively low temperatures. The present study is for evaluating the performance of the humidifier with coconut coir as packing material used for air humidification in the solar humidification dehumidification (HDH) desalination plant. Experiments were carried out on the humidifier packing for different flow rates of water and its temperature. Humidifier range, effectiveness and efficiency, evaporation rate of water, heat and mass transfer rates are studied by experimentally for different flow rates of hot water and its temperature. The hot water flow rate is varied from 125 to 225 LPH with an increment of 25 LPH and water temperature from 38 to 54°C. It is found that at water flow rate of 200 LPH and at 0.55 m3/s volume flow rate of air, effectiveness of humidifier found to be maximum of 0.74.

Boosting stepped solar still system efficiency with affordable natural energy absorbers

In this paper, built the water desalination unit based on the humidification dehumidification (HDH) process powered by solar energy was examined. The unit uses a humidifier of the packing type (HPT) and the dehumidifier (condenser) made a concentric helically tube and shell heat exchanger was investigated. The dehumidifier was used to condensate water vapor from humid air. The Nusselt number (Nu) inside the helical tube was discussed in many studies before, although it is not mentioned before the Nusselt number outside the helical tube for a mixture fluid. In the current study cold water in passing inside a concentric helical tube, while a hot humid air passing over the external surface of the concentric helical tube. The concentric helical tube is positioned inside an insulated shell. Different air flowrates were used, and the experimental results were used to induce a new empirical equation for the shell’s Nusselt number. The water desalination unit was examined by using the solar collectors as a heating source for the saline feed water and the introduced air to the humidifier, and it is found that the freshwater productivity was 8.60 kg/day and to reduce the carbon dioxide released by 4600 g/day.

Solar humidification-dehumidification desalination technology has been reviewed in detail in this paper. This review would also throw light on the scope for further research and recommendations in active distillation system by humidification and dehumidification (HDH). Also in this article, a review has been done on different types of (HDH) systems. Thermal modeling was done for various types of humidification and dehumidification(HDH) distillation system. From the present review, it is found that the humidification-dehumidification desalination process HDH will be a suitable choice for fresh water production when the demand is decentralized. HDH is a low temperature process where total required thermal energy can be obtained from solar energy. Capacity of HDH units is between that produced by conventional methods and solar stills. Moreover, HDH is distinguished by simple operation and maintenance. Also from the present condensed review, it was observed that an increase in evaporator and condenser surface areas significantly improves system productivity. But prior to implementing any techniques in design improvement, it is necessary to optimize the MEH unit by optimizing its component size to understand the effect of feed water and air flow rates. Although a fair amount of simulation studies have been conducted in the past, further design simulation is required to fully understand the complicated effects of air and water flow rates, the optimum size of individual components or modules of the unit and to generate a comprehensive model for the system.

Experimental evaluation of a two-stage indirect solar dryer with reheating coupled with HDH desalination system for remote areas

Sweeping gas membrane distillation: Numerical simulation of mass and heat transfer in a hollow fiber membrane module

Theoretical study on a cross-flow direct evaporative cooler using honeycomb paper as packing material

The lack of freshwater resources has prompted researchers to find other water desalination processes. In this article, a new experimental set up for humidification–dehumidification operating on the principle of an airlift pump was experimented. Experimental work investigates the main operating parameters of a proposed desalination process working with an air humidification—dehumidification method. The principal objective of this investigation was the determination of the humid air behavior through single stage of an airlift humidification–dehumidification system. The experimental work studied the influence of the operating conditions such as the water temperature and the initial level of water in the riser and the airflow rate on the performance of the setup. The experimental results show that the production rate of the system increases with the both increase of the sea water temperature and the airflow rate. The productivity of the system is strongly affected by the sea water temperature, airflow rate and slightly affected by the initial level of water in the riser. Within the studied ranges, the maximum productivity of the system reached to 4 kg/h, at Tw = 85°C and m a = 5 kg/h.KeywordsAirlift pumpAir humidification– dehumidification processDesalination system

The main problem with existing desalination technologies is that they consume high input energy to generate fresh water. Secondly, this energy demand is usually met by conventional sources of energy such as fossil fuels. With limited conventional energy reserves predicted for the future, the focus is on the utilization of renewable sources of energy such as solar, wind, and geothermal energy for powering desalination systems. Such a transformation would make the desalination systems more energy efficient, sustainable, and economical. In this paper, a novel concentrated solar powered (CSP) flash desalination system with direct heating and pressure modulation is presented. A lab-scale prototype was designed, manufactured, and tested for feed water collected from the Arabian Sea and in climatic conditions of Al-Khobar city in Saudi Arabia. The effect of three process parameters, namely, feed water temperature (30–40 °C), feed water flow rate (0.003–0.006 kg/s), and vacuum pressure (0.1–0.3 bar) on distillate production, was investigated. System modelling and optimization were done using Design Expert software and Response Surface Methodology (RSM). The central composite design technique was employed for the optimization of process parameters. The adequacy of the developed distillate production model was verified by ANOVA. The optimum values of feed water temperature, flow rate, and vacuum pressure are reported to be 40 °C, 0.005 kg/s, and 0.1 bar, respectively, resulting in distillate production of 0.001 kg/s.

In this study, a small-scale two-stage multi-stage flash (MSF) desalination unit equipped with a vacuum pump and a solar parabolic collector (PDC) with a conical cavity receiver were integrated. To eliminate the need for heat exchangers, a water circulation circuit was designed in a way that the saline feedwater could directly flow through the receiver of the PDC. The system’s performance was examined during six days in July 2020, from 10:00 a.m. to 3:00 p.m., under two distinct scenarios of the MSF desalination operation under the vacuum (−10 kPa) and atmospheric pressure by considering three saline feedwater water flow rates of 0.7, 1 and 1.3 L/min. Furthermore, the performance of the solar PDC-MSF desalination plant was evaluated by conducting energy and exergy analyses. The results indicated that the intensity of solar radiation, which directly affects the top brine temperature (TBT), and the values of the saline feedwater flow rate have the most impact on productivity. The maximum productivity of 3.22 L per 5 h in a day was obtained when the temperature and saline feedwater flow rate were 94.25 °C (at the maximum solar radiation of 1015.3 W/m2) and 0.7 L/min, respectively, and the MSF was under vacuum pressure. Additionally, it was found that increasing the feedwater flow rate from 0.7 to 1.3 L/min reduces distillate production by 76.4% while applying the vacuum improves the productivity by about 34% at feedwater flow rate of 0.7 L/min. The exergy efficiency of the MSF unit was obtained as 0.07% with the highest share of exergy destruction in stages. The quality parameters of the produced distillate including pH, TDS, EC and DO were measured, ensuring they lie within the standard range for drinking water. Moreover, the cost of freshwater produced by the MSF plant varied from 37 US$/m3 to 1.5 US$/m3 when the treatment capacity increased to 8000 L/day.

Water desalination presents a need to address the growing water-energy nexus. In this work, a literature survey is carried out, along an application of a mathematical model is presented to enhance the freshwater productivity rate of a solar-assisted humidification-dehumidification (HDH) type of desalination system. The prime novelty of this work is to recover the waste heat by reusing the feedwater at the exit of the condenser in the brackish water storage tank and to carry out the analysis of its effectiveness in terms of the system’s yearly thermoeconomics. The developed mathematical model for each of the components of the plant is solved through an iterative procedure. In a parametric study, the influence of mass flow rates (MFRs) of inlet air, saline water, feedwater, and air temperature on the freshwater productivity is shown with and without the waste heat recovery from the condensing coil. It is reported that the production rate of water is increased to a maximum of 15% by recovering the waste heat. Furthermore, yearly analysis has shown that the production rate of water is increased to a maximum of 16% for June in the location of Taxila, Pakistan. An analysis is also carried out on the economics of the proposed modification, which shows that the cost per litre of the desalinated water is reduced by ~13%. It is concluded that the water productivity of an HDH solar desalination plant can be significantly increased by recovering the waste heat from the condensing coil.

Study of heat and mass transfer through a porous carbon tube as a humidification media for evaporative cooling system with swirl flow

This study presents an energy-exergy analysis of a Humidification-Dehumidification (HD) solar water desalination system. The extensive application of the HD system lies in its low energy consumption and ability to exploit solar energy to supply all the heat energy demands. The unsteady governing equations were solved until the system reached a steady state. The simulations were done with the Euler approach to solving the system of energy balance equations numerically. This study's main goal was to investigate the effect of different configurations of the hybrid system and various operating conditions on the performance of the solar HD water desalination system. The optimum configuration was selected based on thermodynamic and exergy analyses. The effects of important parameters such as inlet water and air mass flow rate in the humidifier and dehumidifier water temperature and mass flow rate on the system's operation were studied. This paper also explored the feasibility of the extra heat as a domestic water heater under various conditions. Based on exergy analysis, it is shown that the solar desalination system with air-water preheater with the power of 1057.9 W had the most exergy destruction in comparison with the two other systems (i.e., water preheater system and air preheater system with the respective exergy destructions of 901.3 W and 75.3 W). Comparing the values of freshwater production, exergy destruction, and exergy efficiency, the solar system with a water preheater was selected as the optimum one.

On the dimensional analysis for solar desalination using humidification-dehumidification processes