Development of a photovoltaic-thermal solar humidifier for the humidification-dehumidification desalination system coupled with heat pump (original) (raw)
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International Journal of Environmental Science and Technology, 2019
Global water scarcity is one of the biggest human concerns in recent decades. Seawater desalination becomes the dominant way to access the new drinkable waters. The present study developed a heat pump-assisted humidification-dehumidification water desalination system. The designed system is equipped with a novel solar humidifier that works based on the free-flow solar water collectors. The effect of air flow rate and mode of the air circulation system on the performance of the designed system was experimentally investigated. The results reveal that raising the air flow rate improved water evaporation rate and the solar humidifier efficiency, while closing the air circuit led to a reduction in the evaporation rate. The maximum evaporation amount and water productivity were around 1.38 and 1 kg/h/m 2 in the average solar irradiance of 877 W/m 2. The closed-loop air circulation system resulted in a significantly higher effectiveness of dehumidification and produced higher desalinated water compared with the open-circuit mode. The lowest specific electrical energy consumption and the highest gained output ratio values of, respectively, 0.15 kWh/kg and 2.36 were observed at the air flow rate of 0.019 m 3 /s/m 2 of solar humidifier when closing the air circulation system.
Experimental investigation of a solar powered humidification-dehumidification desalination unit
DESALINATION AND WATER TREATMENT, 2017
The present work deals with an experimental study of a solar desalination unit using the humidification-dehumidification (HDH) process. A bench-scale desalination unit was designed and tested in Bizerte, Tunisia. Humidification is achieved through a humidifier with saline water falling on its absorber plate, and dehumidification is realized by means of a tubular heat-exchanger condenser. The desalination unit operates with open-water and open-air cycles. Thermal performances as well as fresh water production of the HDH desalination unit were evaluated via measurements of air and water temperatures and flow rates. Measurements were conducted in free and forced convection. Special attention was focused on the influence of air velocity on the fresh water production of the desalination unit. The optimal air velocity, corresponding to the maximum of fresh water production, was found to be 3.34 m/s.
Solar assisted modified variable pressure humidification-dehumidification desalination system
Energy Conversion and Management
Variable pressure humidification technology is proposed for seawater desalination through evaporation at pressure(s) less than atmospheric and subsequent condensation. Two sub-atmospheric humidification processes (process-I and II) utilizing solar heat are proposed and assessed theoretically. The desalinated water production rate, gained output ratio and an economical comparison between processes are made subject to similar operating conditions. It is deduced that, under similar conditions, pressure reduction from 0.9 bara to 0.1 bara leads to approximately 50% increase in the desalinated water production rate in each of the proposed processes. For humidifier pressures less than atmospheric pressure, the maximum gained output ratio for process-II is higher by 139.13% than that of process-I while the distilled water production rate is lower by 5.71%. Unlike other variable pressure desalination processes, there is no need to use compressor when the vacuum pump is present. To have a comprehensive study of the proposed systems and determine their feasibilities, a cost analysis is conducted. The result of cost analysis indicates that the total cost per liter of distilled water in two proposed process are 0.
Performance Evaluation of a Solar Humidification-Dehumidification Desalination Unit
2015
This paper is to investigate the use of solar energy in desalination by humidification and dehumid-ification process (HD). Here, a proposal for the desalination unit has been come out with cylindrical shape containing the evaporator in the middle and surrounded by the condenser. The hot feed water coming from the solar thermal system is sprayed at the top of the evaporator where the air flows from the bottom. In the evaporator the air is humidified until it gets out saturated, then introduced to the condenser, where it is dehumidified to obtain the fresh water and circulated back to the evaporator. Practically there are many parameters influence on the performance of this desalination unit, which are environmental, design and operational. In the current study these parameters are taken in consideration to formulate mathematical models which govern the performance of the main components of this unit, which are the evaporator, the condenser and the solar thermal system. The deduced ma...
International Journal of Energy Research, 2020
In previous investigations, humidification-dehumidification (HDH) solarassisted desalination systems were designed produce the daily fresh water during sun hours which lead to big sizes and unsteady systems. In the present study, integration of solar-assisted HDH desalination system with heat recovery and thermal energy storage unit is developed to enhance system productivity, reduces auxiliary power consumptions and system size and assure system continuous operation. The mathematical modelling based on energy and mass conservation equations is presented and solved using iterative techniques by C ++ and engineering equation solver software. Detailed parametric study of the developed system is conducted for wide ranges of operating conditions and design parameters to study the effects of integrating the HDH system with solar collectors, heat recovery and thermal energy storage units on the system performance. The results revealed that (i) this integration improves system productivity and reduces operating cost, (ii) increasing air to water mass ratio and sea water temperature and decreasing ambient humidity decrease water productivity and gained output ratio (GOR) and increase operating cost parameter (OCP) and (iii) increasing air inlet temperature and sea water flow rates increase GOR and decrease OCP. Comparison with previous systems showed that the proposed system reduces the electric heating power of the system at solar noon by 37% at MR = 0.5 and gives daily fresh water productivity (123.7 kg/h) two times more than previous systems with comparable OCP
New solar desalination system using humidification/ dehumidification process
2013
An innovative solar desalination system is successfully designed, manufactured and experimentally tested at Makkah, 21.4 oN. The system consists of 1.15 m flat-plate collector as a heat source and a desalination unit. The unit is about 400 liter vertical cylindrical insulated tank. It includes storage, evaporator and condenser of hot salt-water that is fed from the collector. The heated water in the collector is raised naturally to the unit bottom at which it is used as storage. A high pressure pump is used to inject the water vertically up through 1-mm three nozzles inside the unit. The hot salt-water is atomized inside the unit where the produced vapor is condensed on the inner surfaces of the unit outer walls to outside. The system was experimentally tested under different weather conditions. It is obtained that the system can produce about 9 liter a day per quadratic meter of collector surface area. By that it can produce about 1.6 liters per kWh of solar energy. Moreover the wa...
Desalination, 2004
This paper presents the characteristics of a solar desalination system based on the humidification-dehumidification principle. The system which, can be used in an open or closed cycle for air, is a modular one. It has the following independent components: two solar collectors, an evaporator and a condenser. The first part of the study deals with the presentation of the designed and constructed components. Some experimental results are analysed. They present a general picture of the evolution of the temperature and the humidity between the entry and the exit of the solar collector, the evaporator and the condenser. In the second part, a general mathematical model including the mechanism of heat and mass transfer in the various components of the present desalination system was developed. The theoretical results show that there exists an optimum mass flow rate ratio corresponding to a maximum fresh water product.
Solar Desalination by Humidification-Dehumidification of Air
MATEC Web of Conferences, 2018
The importance of supplying potable water can hardly be overstressed. In many arid zones, coastal or inlands, seawater or brackish water desalination may be the only solution to the shortage of fresh water. The process based on humidification-dehumidification of air (HDH) principle mimic the natural water cycle. HDH technique has been subjected to many studies in recent years due to the low temperature, renewable energy use, simplicity, low cost installation and operation. An experimental test setup has been fabricated and assembled. The prototype equipped with appropriate measuring and controlling devices. Detailed experiments have been carried out at various operating conditions. The heat and mass transfer coefficients have been obtained experimentally. The results of the investigation have shown that the system productivity increases with the increase in the mass flow rate of water through the unit. Water temperature at condenser exit increases linearly with water temperature at humidifier inlet and it decreases as water flow rate increases. HDH desalination systems realised on also work at atmospheric pressure; hence they do not need mechanical energy except for circulation pumps and fans. These kinds of systems are suitable for developing countries. The system is modular, it is possible to increase productivity with additional solar collectors and additional HDH cycles.
Air humidification–dehumidification for a water desalination system using solar energy
Desalination, 2007
This paper presents a theoretical study of a solar desalination system with humidification-dehumidification which is a promising technique of production of fresh water at small scale (few m 3 /d). A general model based on heat and mass transfer balances in each component of the system was developed and used to optimize the system's nondimensional characteristics. The daily production of fresh water depends on the ratio between the salt water and the air mass flow rates. It was shown that, if this ratio is continuously adjusted for optimum performance, it is possible to produce more than 40 L of fresh water daily per square meter of solar collector surface on a typical July day in Tunisia. Annual performances for open and closed air loop systems are also presented.