In recent years, water stress has become a global crisis due to climate and demographic changes and lifestyle changes. Freshwater production from the sea using various processes is known as the most important solution to deal with this crisis. Among these processes, the humidification-dehumidification process has been considered by the scientific community as a flexible and low-cost method. The present work has investigated the performance of vortex-humidification-dehumidification water desalination cycle. The existing system is a dehumidifier-dehumidifier type, in which a vortex tube has been added. According to the structure of the vortex tube, its hot air outlet has been used to increase the possibility of moisture absorption in the humidifier and its cold air outlet has been used to increase the amount of condensed water in the humidifier. According to the second law of thermodynamics, the performance of the cycle has been studied. In the analysis of multi-flow cycles with heat and mass transfer, the commercial software EES has been used to solve the equations. The fresh water output for specific conditions (sea level, air temperature 35 degrees Celsius and relative humidity 30 percent) is equal to 7.85 kg/h and the research results show that the Gained-Output-Ratio is equal to 1.189. It is shown that the use of the vortex tube and the consequent increase in air temperature at the inlet of the humidifier and the use of the second dehumidifier in the cycle increase the production of fresh water.

Solar humidification-dehumidification desalination is one of the most practical methods for water desalination in small scale for regions far from cities and with low population. The aim of this study is manufacturing and simulation of a solar humidification-dehumidification desalination system with capacity of 20 lit/day. This system consists of humidification and dehumidification units, solar air and water heaters. To this end, first this system is explained and modeled. Then, manufacturing process of solar air heaters and different parts of desalination system is investigated. After the manufacturing process of the desalination system, this system is experimentally tested and the effect of pertinent parameters, such as the temperature of inlet water and air to humidifier; inlet water temperature and flow rate to dehumidifier on the performance of the system and distillate product are investigated. The results show that the effect of water temperature on the fresh water produced is more than air temperature. Moreover, using the chilled water, which has a temperature in the range of water well temperature, in the dehumidifier inlet leads to an increase of 31 % in the fresh water produced. Also, the best water flow rate to the dehumidifier inlet is 0.12 kg/s. Finally, experimental and simulation results are compared with each other and good consistency is seen.

The humidification-dehumidification system is one of the desalination technologies that can utilize non-fossil thermal sources and requires insignificant input energy. This system is usually suitable for rural areas and places far from the main sources of energy. The purpose of this study is to obtain the most suitable working conditions and dimensions of this system. In this research, thermodynamic modeling was first performed for a simple type of the system (water-heated); then, the effect of parameters on the system performance was investigated. Modeling was conducted through a numerical simulation; furthermore, the assumption of the saturation of exhaust air from the humidifier was also considered in the mentioned code. Afterward, a comparison was made between two different forms of the system, and the proper form was chosen for the rest of the research. Moreover, through heat transfer equations, the dimensions of the two main parts of the system, i. e., humidifier and dehumidifier, were calculated. Besides, multi-objective optimization was carried out for two objective functions, i. e., gained output ratio (GOR) and the system volume, to reduce the space occupied by the system and reach the desired efficiency simultaneously. The optimization was performed using a simulation program, and results were obtained for different weights in order to optimize each objective function. For instance, 379 liters of freshwater can be produced in a day with a total volume of 48 liters for the humidifier and the dehumidifier in the optimized system.

In this research and for the first time, the performance of hybrid solar-gas turbine power plants modified with humidification-dehumidification (HD) desalination process was simulated with TRNSYS. The system included a 4. 6 MW gas turbine, solar tower and HD process with air heater and open cycle for water and air. The results showed that in the hybrid solar-gas turbine power plants, the solar power supplied about the 35-45% of required energy and the amount of fossil fuel consumption was reduced. Also, the emission of CO2 was declined for about 40%. The electric power and efficiency of hybrid system was slightly lower than gas turbine only due to the pressure losses in piping and receiver of solar system. The results of HD desalination indicated that the increase in the temperature and relative humidity of the inlet air increased the amount of fresh water production and increase in the temperature of inlet saline water declined its production. Moreover, the amount of fresh water production had an optimum value respect to the mass flow rate of air and with increasing the air flow, the amount of fresh water production increased and then decreased. In addition, if the mass flow rate ratio of saline water to dry air was equal to 1. 8, the gain output ratio (GOR) had a maximum value of 2. Variation of GOR in terms of returned air at different inlet air temperatures was explained.

Oil and gas drilling produce saline brine, posing a threat and great risk to the environment. Desalination is a pathway to freshwater production and brine removal, however, the energy required for processing and highly concentrated brines curtail the approach. Solar desalination humidification dehumidification (SDHDH) systems are a low energy and economical response that solves the problems. The current study aims to demonstrate saltwater solar-desalination, an innovative SDHDH design, used to process the waste materials. The method was successfully tested at full scale as follows: In a 400 m2 application containing 600 m3 saline-water, the total dissolved solids (TDS) were equal to 141 g l-1, requiring an input of 196. 2 kW electrical energy. As a result of SDHDH 266 m3 of freshwater was obtained, with TDS equal to 210 mg l-1. The water-recovery percentage achieved was 44%. The salt removal efficiency was near 100%. Surface-time efficiency varied, between 8 to 30 l m-2day-1. SDHDH use is an effective mechanism to elute freshwater from concentrated brines, maximizing productivity, and lowering hazardous impact to the environment providing benefits to ecosystem and human services alike.

The air humidification-dehumidification method is a good option for decentralized freshwater production because of no need for high temperature operation. The main disadvantage of these systems is their dependence on direct sunlight. to solve this problem, using the sun's thermal energy storage during the day and using this energy during the night can be a very good option that can be achieved using phase change materials. In the present work, it is also possible to continue the desalination process after sunset, by equipping the solar collector with phase change material from two different types of paraffin wax. MATLAB software has been used to solve the equations governing the components of the desalination system. According to the results, the temperature of the output water from the solar collector plays a significant role in the amount of fresh water produced. The results also confirm that the use of phase change material leads to more than 9% increase in fresh water production. Another important result is that in the phase change materials the melting process speed is substantially higher than the freezing process speed.

In this study, a novel solar water desalination system was proposed. The designed system worked based on the humidification – dehumidification (HD) method. It was comprised of a photovoltaic-thermal (PVT) evaporator, a condenser, fresh and saline water tanks, an air blower, and a water pump. The performance evaluation tests were conducted at three velocities of air leaving the exhaust pipe (1, 1. 5 and 2m/s) and three levels of saline water passing over the photovoltaic module (94, 189 and 283kg. h-1 per m2 collector surface). The results showed that the highest evaporator efficiency was about 80% and the maximum daily evaporated water was about 7. 4kg, which were observed at the water flow rate of 189kg. h-1m-2 and the air velocity of 2m/s. Whereas, a maximum condenser effectiveness of 61% and fresh water production of about 4. 8kg per day were found at the water flow rate of 189kg. h-1m-2 and the air velocity of 1m/s. Although operating temperature of the conventional photovoltaic module was considerably higher than the PVT collector at the different working conditions, its electrical efficiency was also higher due to the more absorption of solar energy.

Humidification-dehumidification (HD) desalination has been identified as a sustainable, reliable, and energy-efficient technology for producing freshwater on a small scale. VP-HD systems operated at one-stage, multi-stage, and multi-feeding vacuum humidification-over atmospheric pressure dehumidification arrangements can be the recent modifications of an HD system. The present study offers a theoretical investigation and experimental verification of two VP-HD systems, encompassing both sub-atmospheric pressure humidification and over-atmospheric dehumidification. Two designs are evaluated, one comprising a three-stage humidification setup and the other featuring a three-feeding one-stage humidification apparatus. The results show which design has better performance than previous conventional and variable pressure HD systems. The parametric analysis reveals that an upsurge in freshwater generation is observed with an increase in air temperature, feed salinity, and a decrease in humidifier pressure. Additionally, an optimal water-to-air ratio is identified. The study further highlights that multi-stage humidification yields better results concerning freshwater productivity and specific power consumption. Three-stage humidification is found to be the most efficient in terms of freshwater production and specific power consumption, achieving the highest values of 1.93 L h-1 m-2 and 0.21 kWh L-1, respectively. The agreement between theoretical and experimental outcomes is deemed satisfactory.

In this paper, the performance of a hybrid humidification-dehumidification (HDH) desalination system is experimentally studied. The system operates as an Open-Air Closed-Water cycle and utilizes a solar air heater to heat the input air to the humidifier. An Ammonia absorption refrigeration cooling cycle is used to condense the humid air, producing fresh water. Parameters such as temperature and relative humidity were measured in different stages of the system by using humidity and temperature sensors, and the thermodynamic analysis was carried out using EES software. The effects of the mass flow rate and temperature of the inlet air flow on the rate of desalination, COP, GOR, and the efficiency of the humidifier and the dehumidifier were studied. The analysis proved that the highest rate of water production and GOR were 150 g/h and 1.2, respectively. It was also perceived that with an increase in the air mass flow rate, the rate of water production and COP increased, while GOR and the efficiency of the dehumidifier diminished. This is while the efficiency of the humidifier remains nearly constant. It was also concluded that an increase in the temperature of the input air, leads to a fall in the GOR, while the other parameters show an increasing trend. Following the economic analysis of the system, the CPL was found to be $0.16 /L.

In this study, the performance of solar desalination by humidification-dehumidification of closed air and water in Ahvaz city was investigated. This desalination includes a collector, condenser, salty water, freshwater tanks, air blower, and water pump. The evaluation of the system was done at three levels of air velocity (3, 4, and 5 m/s) and at three pump discharge levels (2, 4, and 6 liters/min). The results showed that the lowest daily average of evaporative efficiency was about 56%, which obtained at air velocity of 3 m/s and water discharge of 2 liters/min, and the highest value of that was about 79%, which obtained at air velocity of 5 m/s and water discharge of 6 liters/min. Also, the highest daily average of condenser efficiency was 21. 52%, which was obtained at the air velocity of 3 m/s and discharge water of 6 liters/min. The lowest freshwater was obtained at air velocity of 5 m/s and 2 liters/min, and the highest value was obtained at air velocity of 3 m/s and 6 liters/min.