Performance evaluation of humidification-dehumidification (HDH) desalination systems with and without heat recovery options: An experimental and theoretical investigation

Desalination 436 (2018) 161–175

Contents lists available at ScienceDirect

Desalination journal homepage: www.elsevier.com/locate/desal

Performance evaluation of humidification-dehumidification (HDH) desalination systems with and without heat recovery options: An experimental and theoretical investigation

T

⁎

Syed M. Zubair , Mohamed A. Antar, Samih M. Elmutasim, Dahiru U. Lawal Mechanical Engineering Department, KFUPM Box # 1474, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

A R T I C L E I N F O

A B S T R A C T

Keywords: Humidification-dehumidification (HDH) Thermal desalination technology The gained-output ratio (GOR) Experimental Analytical Effectiveness

Humidification dehumidification (HDH) desalination system is a thermal-based desalination technology that is suitable for small-scale water desalination applications. In this paper, we present an experimental and thermodynamic analysis of the energetic performance of two HDH cycles. The HDH cycles considered are the basic open-air open-water (OAOW) cycle and the modified closed-water open-air (CWOA) cycle with the options of brine recirculation. An experimental investigation is performed on the modified cycle to validate the theoretical model that is used to assess the energetic performance of both the basic and modified cycles. The theoretical model is found to be in a good agreement with the experimental data with a maximum percentage deviation of 5% from the experimental data. Furthermore, limiting cases of the system are explored. Within the limiting cases, the modified cycle recorded about 100% improvement in the energy performance over the basic cycle due to heat recovery process associated with the modified cycle. Additionally, a cost analysis was performed to determine the cost of freshwater production by the presented desalination cycles. Results show that the freshwater price varied from 4.10 to 6.55 $/m3 and 0.79 to 2.25 $/m3 for the basic OAOW HDH cycle and the modified CWOA HDH cycle, respectively.

1. Introduction Over the last century, the demand for potable water has substantially increased due to the increase in human population, activities, and development such as agricultural, industrial and socio-economic development. In an attempt to address the problem of freshwater shortage, several desalination techniques have been developed to desalinate saline water. Humidification-dehumidification (HDH) desalination system is one of the most promising desalination technologies for a decentralized small-scale desalination process [1]. HDH desalination process has been used, investigated and improved over the years. These systems are suitable for small-scale freshwater production, and offer numerous advantages over other desalination technologies; however, the main drawback remains. That is, it requires a relatively highenergy compared to other desalination technologies [2]. HDH systems have an advantage over some other technologies, such as reverse osmosis, in that they involve a relatively simple, inexpensive components. It can operate over a wide range of raw water quality without the need for complex maintenance operations [2]. These systems are also reported to have a higher GOR over solar still. Other benefits of HDH

⁎

systems include the ability to operate at low temperature, and the feasibility of being powered by sustainable energy resources such as solar and geothermal [3]. These systems may be classified according to whether air or water is heated and to the nature of air or water stream [4]. This work has been focused on open-air open-water (OAOW) and closed-water open-air (CWOA) HDH cycles. Many studies on HDH system have been directed on optimizing and improving the performance of its components with the aim of improving the overall system performance. An innovative design that can reduce the dehumidifier size through direct contact HDH process has been studied by Niroomand et al. [5]. In the proposed system, air is dehumidified by spraying cold water to the hot and humid air stream, instead of using the conventional indirect condensers for the dehumidification process. Their results showed that the water production increases with decreasing initial velocity and diameter of water droplets. It was also found that the freshwater production and efficiency of the system increases with increasing hot water flow rate and temperature as well as by decreasing the cold water flow rate and temperature. Klausner et al. [6] used a direct-contact dehumidifier in combination with a shell-and-tube heat exchanger to provide enhanced condensation

Corresponding author. E-mail address: [email protected] (S.M. Zubair).

https://doi.org/10.1016/j.desal.2018.02.018 Received 23 October 2017; Received in revised form 12 February 2018; Accepted 12 February 2018 0011-9164/ © 2018 Elsevier B.V. All rights reserved.

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Nomenclature

n P Q̇ T X x y

Acronyms CAOW COE CWOA EPC GOR HCR HDH MR OAOW RR SEC

closed-air open-water the unit cost of electricity closed-water open-air annual electric power cost the gained output ratio heat capacity rate ratio humidification-dehumidification the water-to-air mass flow rate ratio open-air open-water recovery ratio (%) specific energy consumption

Greek Symbols ε ω L

effectiveness absolute humidity (kgw kga−1) the specific cost of operating a labor ($ m−3)

Subscripts a b cw deh fluid fw hum in intake p 0,1,…

Symbols CF CP CT cP f h hfg i LC ṁ

amortization years (life of the system) Pressure (kPa) heat transfer rate (kW) temperature (°C) salinity (ppm) the fraction of saline water mass flow rate (kg/s) the fraction of brine mass flow rate (kg/s)

annual capital cost ($ yr−1) unit product cost ($ m−3) total annual cost ($ yr−1) specific heat capacity at constant pressure (kJ kg−1 K−1) plant availability specific enthalpy (kJ kg−1) specific enthalpy of vaporization (kJ kg−1) interest rate annual labor cost ($ yr−1) mass flow rate (kg/s)

air brine cooling water dehumidifier working fluid freshwater humidifier entering entering the stream pump state points

injected to the dehumidifier and vice versa has been investigated extensively by several researchers [15–21], all in an attempt to improve the performance of HDH system. From the above-cited work, we found that there is a need to systematically improve the cycle performance of HDH system by modifying the cycle. Therefore, the objective of this paper is to experimentally and analytically analyze the performance of a basic open-water open-air (OWOA) cycle and improve the cycle performance through a modified closed-water open-air cycle (CWOA). The modified closed-water open-air is achieved by incorporating heat recovery options.

and improved heat recovery for the cycle. Dawoud et al. [7] theoretically investigated different possible cooling techniques for the condenser of a seawater greenhouse desalination system. The possible cooling techniques include; evaporative cooling for surface seawater, a cooling machine to cool the condenser coolant in a closed loop, or to utilize deep seawater as a condenser coolant. They suggested that evaporative cooling with surface seawater seems to be the most suitable cooling technology for the greenhouse condenser. Ettouney [8] assessed different configurations of the HDH tower. The layouts included the conventional humidification system combined with each of the following units; lithium bromide absorption-desorption system, water condenser, vapor compressor, and water condenser, to condense the water vapor from the air. He showed the need to determine the most efficient design and operating conditions that result in a minimum product cost. In another study, Narayan et al. [9] assessed the thermodynamic performance of various HDH cycles through a theoretical cycle analysis. They also proposed different novel highperformance cycles including multi-extraction, multi-pressure systems. It is shown that the proposed high-performance cycle can attain a GOR > 5, which is expected to outperform many existing HDH systems. Sharqawy et al. [10] numerically investigated the design, performance, and optimization of two HDH cycles. They presented first-law based thermal analysis model, as well as performance charts, which can be used to determine the size of HDH systems under different design conditions. Aburub et al. [11,12] experimentally assessed the performance of another configuration of HDH system, which is described as a packed-bed cross-flow humidification-dehumidification desalination system. The system is a closed water (brine recirculation), and open-air configuration. To enhance the performance of HDH desalination system, many modifications have been made. A novel HDH system driven by forced convection was invented by Brendel [13,14]. In this configuration, a forced convection was used to extract water from the dehumidifier and injected to the dehumidifier under balanced temperature profiles. Thermal balancing by extracting air or water from the humidifier and

2. System description and mathematical modeling 2.1. The basic cycle: open water open air (OWOA) HDH system The basic cycle is an open-air and open-water loop as shown in Fig. 1. The seawater is passed through the dehumidifier and then heated in the heater before it is sprayed in the humidifier. A portion of sprayed hot saline water evaporates into the air stream, while the rest is rejected through the bottom of the humidifier, as a rejected brine. Air flows in a counter-flow direction through the packing material placed in the humidifier, where the air is heated and humidified through the direct contact with the sprayed hot water. The hot and humid air then flows to the dehumidifier where water vapor present in the humidified air condenses to produce fresh water, and the cold air is ducted out of the dehumidifier. 2.2. The modified closed-water open-air (CWOA) HDH system The modified closed water open-air HDH System, as illustrated in Fig. 2, is similar to the basic cycle of open water open-air loop, except that the modification is made in the water loop. In Fig. 2, the saline water enters the dehumidifier and absorbs heat from the hot and humid air. A portion of the preheated saline water is admitted into a tank as a make-up water, while the rest is discharged. The saline water in the 162

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Fig. 1. Open-air open-water HDH system.

2.3. Mathematical modeling

tank is then heated and sprayed in the humidifier where part of it evaporates and the unevaporated seawater is collected, ducted and recirculated back to the tank, to close the water loop. The comparison of various basic and modified basic cycles of HDH system in terms of gained output ratio, as reported in the literature [9], is presented in Table 1. In both of these figures, T, Twb and Tdb are the water temperature, wet bulb temperature and dry-bulb temperature of the air, respectively.

In order to achieve objectives of the present study, a thermodynamic cycle analysis has been performed to assess the performance of two HDH cycles. In performing the analysis, the following assumptions have been made [10]:

• The system involved operates under steady-state conditions.

Fig. 2. Modified closed-water open-air HDH system.

163

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Table 1 Comparison of HDH cycles [9]. Cycle CAOW CAOW CAOW CAOW CWOA CWOA

GOR -

air heated cycle multi-stage air heated cycle (4-stages) modified air heating water heated cycle water heated cycle modified air heating

MR =

ṁ w (h w, out − h w, in ) = ṁ a (ha, in − ha, out ) − ṁ fw hfw

(2)

To achieve objectives of the current study, experimental investigation of the performance of a modified CWOA HDH system was conducted. An experimental set-up equipped with a data acquisition system to record readings from thermocouples on a real-time basis was assembled. The data obtained from the experimental program are analyzed and compared with the model results. 3.1. Set-up description The system under consideration is a modified water heated closedwater open-air (CWOA) system. The humidifier and dehumidifier units are made of a plexiglas material, which is in the form of vertical rectangular ducts. The dehumidifier has cross-sectional dimensions of 30.5 cm × 30 cm and a height of 122 cm. Three condensers made from copper tubes and aluminum fins are installed inside the dehumidifier for an effective condensation of water vapor. The make-up tank (62×36×43 cm3) equipped with four electrical heaters (1.2 kW, 1.2 kW, 1.2 kW and 2 kW) is filled with raw water having a salinity of 2500 ppm. Glass wool blanket batts insulation is used to cover the tank from all sides to minimize heat loss to the ambient. The humidifier has cross-sectional dimensions of (122 × 30.5 × 30 cm3). Three structuredtype packing-material (cellulose pads) having a total height of 65 cm is installed inside the humidifier. To eliminate the problem of carrying over of water droplets with air, a drift eliminator followed by a loofah packing was used. Also, to avoid the growth of biological fouling, the fill material was periodically cleaned after every two weeks and replaced with the new ones, after continuously operating the experiments for about two months. A photograph of the actual setup showing the main components of the system, is shown in Fig. 3. The system is operated at an atmospheric pressure, which is assumed to be 101.325 kPa. The hot water tank is insulated to reduce heat loss and ensure steady and constant water temperature. The feed water is pumped through the dehumidifier using a small centrifugal pump, and ball valves are used to regulate the water flow rate. K-type thermocouples are installed at the inlet and outlet of the air and water streams to measure the dry- and wet-bulb temperatures, and water temperatures in the system. The thermocouple junction for wet-bulb temperature measurements is wrapped by a wet wick supplied by water from a gravity feeding syringe. All the measuring sensors are connected to the National Instrument (NI) data acquisition system (IN cDAQ-9174 module). While all measured values are monitored and stored on a computer using a Lab View code. Water flow rates are measured using in-line flow meters, a glass tube rotameter (Omega FL50000) of ± 5% accuracy having a range of 4–36 LPM. Air at room temperature is blown through the humidifier and packing material by an axial flow air fan installed at the humidifier entrance. The fan provides three different air flowrate of 0.055, 0.066 and 0.08 kg/s. The measured quantities (distillate mass flowrate, dry bulb, wet bulb, and water temperatures) were used in Eqs. (8)–(12) to calculate the humidifier and dehumidifier

Heater energy balance equation (for the basic cycle) can be written as: (3)

The heater mass and energy balance equations (for the modified cycle) gives,

ṁ w − yṁ b ṁ w

(4)

where x presents the fraction of mass flowrate, which is used as a makeup, and y is the fraction of rejected brine mass flow rate that is recirculated to the tank (heater).

̇ + yṁ b hb + xṁ w h w, in ṁ w h w, out = Qin

(5)

The humidifier mass and energy balance equations are:

ṁ b = ṁ w − ṁ fw

(6)

ṁ w h w, in − ṁ b hb = ṁ a (ha, out − ha, in)

(7)

The effectiveness of the dehumidifier is given as [10,20]:

εdeh = max

ha, in − ha, out h w, out − h w, in , ha, in − ha, out , ideal h w, out , ideal − h w, in

(8)

Similarly, the effectiveness of the humidifier is expressed as [10,20]:

εhum = max

ha, out − ha, in h w, in − h w, out , ha, out , ideal − ha, in h w, in − h w, out , ideal

(12)

3. Experimental work

The presented model is based on a thermodynamic analysis where mass and energy balances are applied on each cycle components that are illustrated in Figs. 1 and 2. Dehumidifier mass and energy balance equations are: (1)

ΔHmax, cold ΔHmax, hot

(11)

The above set of equations were solved using Engineering Equation Solver (EES) software, which solves the equations simultaneously through an iterative process.

balance equations.

x=

ṁ w ṁ a

HCR =

ṁ fw = ṁ a (ωin − ωout )

(10)

Another metric used in this study is water-to-air mass-flow rate ratio (MR), and the modified heat capacity ratio, which are defined as [16]:

0.78 0.85 3.5 2.5 2.6 3.5

• Heat losses to the surroundings are neglected • Pumping and fan powers are negligible compared to thermal energy input. • Properties are evaluated at atmospheric pressure, while the properties of sea water are based on work of Sharqawy et al. [21]. • Moist air leaves both the humidifier and dehumidifier at 90% relative humidity. • The feed water salinity is 35 g/kg. • Kinetic and potential energy terms are neglected in the energy

̇ = ṁ w (h w, out − h w, in) Qin

ṁ fw hfg ̇ Qin

GOR =

(9)

The ideal enthalpy of outlet air is taken at the temperature of inlet water, while the ideal enthalpy of outlet water is measured at the inlet air temperature [20]. The most important performance indicator of HDH system is the gain-output ratio (GOR), which is defined as the energy performance index of a HDH system. It is defined as the ratio of latent heat of vaporization of fresh water to the amount of heat utilized to produce it, which is expressed as: 164

Desalination 436 (2018) 161–175

S.M. Zubair et al.

the system performance parameter, GOR. EES provides tools to perform the sensitivity analysis on the measured values. It is important to note that K-type thermocouples and flowmeters (FL50000) have an uncertainty of values of ± 0.1 °C and ± 5%, respectively. An uncertainty of ± 0.5% was calculated for air mass flow rate. The graduated cylinder used to measure the amount of produced freshwater has an accuracy of ± 12 ml. The uncertainty for the experimental GOR is then calculated. The results of uncertainty analysis for the component effectiveness, and the experimental GOR are presented in appendix A.

4. Results and discussion The first step in any reliable model development is the model validation. An experiment was performed to validate the mathematical model developed in this study. The experimental performance of the modified CWOA HDH system is evaluated by calculating the gain output ratio of the system. Also, the variation of system performance with the operating conditions is investigated by changing the operating parameters, which includes the mass flow rate ratio (MR) of water-toair and total heat input to the system. The mass flow rate ratio is obtained by varying the water flow rate only, while the volumetric flow rate of air is kept constant by fixing the fan speed. Fig. 4 illustrates the validation results obtained for the system GOR at different mass ratio and total heat input. As observed in this figure, the gain output ratio increases with the mass flow rate ratio, which has a direct relationship with water flow rate. Increasing the feed water flow rate generates more vapor in the humidifier, and consequently more condensate from the dehumidifier, resulting in higher system GOR, which has a direct relationship to fresh water flow rate. The system GOR is also found to decrease with increasing total heat input. This is because the energy input to the system has an inverse relationship with GOR, as presented in Eq. (10). The presented model is observed to be in a good agreement with the experimental data as the maximum model deviation is calculated to be within ± 5% of the experimental values. Results also showed that the system has an experimental and theoretical maximum GOR of 0.4 and 0.42, respectively, at the mass flow rate ratio of 1.81. The low experimental GOR value is due to the poor humidifier effectiveness (25 to 54%), as shown in Fig. 5, which directly translates to low evaporation rates, and consequently low system GOR values. Next, we defined the limits for components effectiveness, where the system performance will be explored within

Fig. 3. A photograph showing main components of the experimental set-up.

effectiveness values, gained output ratio, mass flowrate ratio, and the modified heat capacity ratio of the system. In order to calculate the distillate mass flowrates; 900 cm3 of condensate is collected and measured using a graduated measuring cylinder. The sample collection time is recorded for each data set. The condensate mass flowrates are then calculated by dividing the mass of collected distillate by the respective time duration.

3.2. Uncertainty analysis The uncertainty is usually evaluated in the calculated results obtained from experimental investigations. Since we used temperature sensors and flowmeters to measure the conditions of operating parameters, it is essential to evaluate the effect of these measured values on

Fig. 4. Impact of mass ratio on gain output ratio at a different total heat input.

165

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Fig. 5. Variation of humidifier effectiveness with MR at a heat input of 5.6 kW.

rate ratio for the basic cycle. This figure is based on the upper and lower limits of components effectiveness, The GOR of the system is observed to increase with MR until it reaches a peak and then decreases with a further increase in MR. This is because the sprayed feed water was flooding the circulating air which results in a reduction in water vapor carried by air, and thus a reduction in system GOR. Another reason for this behavior may be attributed to the fact that the maximum effectiveness of the humidifier changes from the effectiveness of water to the effectiveness of air, which indicates lower water temperatures at the inlet of the humidifier, therefore lowers the evaporation rate and GOR of the system. Another observation can be seen from this figure, the GOR increases with an increasing effectiveness of both the humidifier and dehumidifier. This is due to the fact that higher effectiveness implies high evaporation and condensation rate, and consequently higher GOR. Fig. 7 shows the influence of mass ratio on GOR at different components effectiveness values for zero brine recirculation (basic cycle) and different percentages of brine recirculation (modified cycle). The GOR of the system is noticed to jump from a maximum of 0.35 (zero recirculation) to a value of approximately 0.7 (100% brine recirculation), representing about 100% improvement in the system energy performance. The effect of percentage brine recirculation is also presented in the figure, where we noticed an increase in system GOR due to

Table 2 Components effectiveness valid for recirculation system. Dehumidifier effectiveness (%)

Ranges of humidifier effectiveness (%)

50 60 and 70 80 and 85

40–60 40–53 40–47

and outside the defined limits of the component effectiveness values. After model validation against the experimental results, the limits for components effectiveness values were defined. These limits are defined by considering the basic condition that the temperature of brine recirculated back to the heater (Tw4) should be greater than that of make-up water coming from the dehumidifier (Tw2). To determine the limits, we consider MR ranging from 1 to 3, with a step change of 0.5. The main findings from the determination of components effectiveness limits are summarized in Table 2. The detailed analysis of components effectiveness limits, is presented in Appendix B. By considering the above limits for components effectiveness, the performance of both the basic cycle (no brine recirculation) and modified cycle (with brine recirculation) is investigated, it is shown in Fig. 6. It shows the variation of GOR of the system with the mass flow

ε

ε ε ε ε ε

ε ε ε ε

Fig. 6. Impact of mass ratio on gain output ratio at different components effectiveness values (basic cycle): (a) εdeh = 0.50, and εdeh = 0.85.

166

Desalination 436 (2018) 161–175

S.M. Zubair et al.

ε

ε

ε ε

Fig. 7. Effect of MR on GOR for zero brine recirculation (basic cycle) and different percentages of brine recirculation (modified cycle).

at which the modified cycle begins to shift towards the basic cycle (0% circulation). The impact of moving the dehumidifier effectiveness outside its limiting cases on the system performance, is presented in Figs. 9 and 10. Fig. 9 is noticed to exhibit a similar behavior, except that the point of intersection occurred at different mass flowrate and heat capacity rate (HCR) ratios. As the dehumidifier effectiveness decreases, the point of intersection is observed to occur at lower MR. At the point of intersection and beyond, the performance of basic cycle begins to surpass that of the modified cycle. This shows that this region is sensitive to the dehumidifier effectiveness. The energy associated with makeup water is attained at the dehumidifier, which makes the dehumidifier effectiveness more dominant factor for the basic cycle as compared to the modified cycle that utilizes less makeup water and more brine recirculation. Fig. 9(d) demonstrates the fact that the system has returned to its working range (limiting case for components effectiveness) as the point of intersection, is observed to disappear. Fig. 10 illustrates the effect of moving the humidifier effectiveness outside its limiting cases (humidifier effectiveness is fixed at 80%), which does not fulfill the valid range for which mixing is justifiable. The points of intersection also occurred in this figure as well because of the violation of the conditions that warrant brine recirculation. Similar to Fig. 9, these points are also noticed to move from higher MR to lower MR as the dehumidifier effectiveness decreases. This supports the fact that point of intersection marks the region of dominance of the basic cycle, which is proportional to the dehumidifier effectiveness. A comparison between the modified closed-water open-air (CWOA) cycle and other basic HDH cycles is presented in Table 3. It can be noticed that the modified CWOA cycle yield the best performance in terms of GOR for the same system operating conditions. The comparison is done under the following conditions: the heat input is 4.5 kW, water inlet temperature is at 24 °C with a mass flow rate of 0.07 kg/s. air inlet temperature is at 26 °C and its relative humidity is taken to be 95% at the inlet and outlet of dehumidifier and humidifier, respectively. The humidifier effectiveness and dehumidifier effectiveness are taken to be 50% and 80%, separately.

an increase in the quantity of brine recirculated. This is mainly due to an increase in overall temperature of the sprayed water, which generated more vapor and consequently higher GOR. This happened because the recirculated brine is expected to contain a considerable amount of heat, which is higher than that associated with make-up water. It can be seen from the figure that it reaches a maximum value and then drops at some percentage of the brine recirculation. This can be explained by the fact that the maximum effectiveness definition changes from water to air at those points, leading to a drop in GOR of the system. This figure also shows the extreme limits of effectiveness of the components. The system performance for other components effectiveness values within the limits at different percentage of brine recirculation, are illustrated in Fig. 8. It is obvious that both the humidifier and dehumidifier effectiveness influences GOR of the system. However, the effect of dehumidifier effectiveness on GOR is noticed to be greater than that of humidifier effectiveness, as reported in [9]. For instance, an increase in the dehumidifier effectiveness from 50% to 85% at 43% humidifier effectiveness showed about 74% improvement in GOR of the system. It is important to note that a higher dehumidifier effectiveness translates to higher condensation rate of the water vapor. In all cases, the system performance is seen to improve with an increase in brine recirculation. The recirculated brine is associated with a considerable amount of heat, which contributes to the feed mass flow rate entering the humidifier. This explains the reduction in performance as the percentage of circulated brine reduced from 95% to 10%, i.e., as the system moves from the modified cycle towards the basic cycle. The enhancement in the system performance for the modified cycle justifies the idea of modification; that is, brine recirculation as a heat recovery process. Figs. 9 and 10 explore GOR of the system at different components effectiveness values that fall outside the valid range of components effectiveness values. The summary of limiting cases for components effectiveness are tabulated in Table 2. The main difference between the results presented in Fig. 8 and Figs. 9 and 10 is that in Figs. 9 and 10, the system has moved outside the range of effectiveness that fulfills the basic condition at which mixing is justifiable. This created a common point of intersection where all the curves cross. At the point of intersection and beyond, the brine recirculation will no longer have more influence on GOR of the system. This is because, at this point, a sort of balancing occurs and the system becomes insensitive to the circulation. The point of intersection can be used as an indicator to determine the range of MR that gives better system performance for the modified cycle (brine recirculation). These points can also give the range of MR

4.1. Desalinated water production cost In this section, cost of fresh (desalted) water from the basic open-air open-water (OAOW) cycle, and the modified closed-water open-air (CWOA) cycle with the options of brine recirculation, is estimated. In this regard, design and operational variables are considered. The main 167

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Fig. 8. Influence of mass ratio on gain output ratio at different components effectiveness for different percentages of brine recirculation (modified cycle).

a single operator for a small plant according to the proposed design.

factors influencing fresh water production cost by HDH system includes fixed capital - mainly equipment, and operating costs - mainly energy costs [22]. The plant fixed charges are treated as a function of both the capital investment and plant depreciation factor. The plant depreciation factor depends on variables such as the plant life expectancy, investments, amortization, and financial parameters [23]. The capital investment cost (Cc) involves the purchase cost of major equipment, auxiliary equipment, construction, management, and miscellaneous. Table 4 summarizes the capital investment cost for the HDH system. These values are adopted from [22,24]. It is worth mentioning that the freshwater cost analysis was performed following the method presented in [24,25], and considering the following assumptions in the economic analysis [24]:

• The annual maintenance cost is estimated to be 1.5% of the capital cost. • The yearly cost of management is taken to be 20% of the labor cost. • No pretreatment costs. • The interest rate (i) is 5%. • The plant life expectancy (n) is 20 years. • The plant availability (f) is 90%. • The land costs may be ignored assuming outdoor location and operating in a rural (deserted) area.

The other assumptions made in estimating freshwater flow rate and specific work consumption used in the cost analysis are: heat input of 4.5 kW, water inlet temperature of 21 °C and mass flow rate of 0.07 kg/ s. Air inlet temperature of 26 °C, at a relative humidity of 50%. Air leaves both the humidifier and dehumidifier at 90% relative humidity.

• The unit cost of electricity (COE) is 0.04–0.09 $/kWh. • The annual operator salary (PS) is 6000 $/year, with the plant using 168

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Fig. 9. effect of mass ratio on gain output ratio at different components effectiveness for different percentages of brine recirculation (modified cycle).

The following expressions were used in estimating the production cost of the desalinated water; The amortization charges can be expressed as:

α=

EPC ($ / yr ) = COE ($ / kWh) × × 365

1)n

i (i + (i + 1)n − 1

The annual labor cost (LC): This can be written as, (13)

LC ($ / yr ) = L ($ / m3) × f × Product (m3/ day ) × 365

where α is the amortization factor, i is the interest rate, and n is the amortization years (life of the system). The annual capital cost (CF): This cost can be obtained by multiplying capital costs by amortization factor. It can be expressed as

(16) 3

where L is the specific cost of operating labor ($/m ), which can be calculated from;

Operator salary ($ / yr ) ⎞ L ($ /m3) = ⎛ Product (m3/ day ) × 365(day / yr ) ⎠ ⎝ ⎜

CF ($ / yr ) = Cc ($) × α (1/ yr )

SW (kWh/ m3) × f × Product (m3/ day ) 3600 (15)

(14)

The annual electric power cost (EPC): It can be expressed as,

⎟

(17)

The total annual cost (CT), is some of the above cost elements, 169

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Fig. 10. Impact of mass ratio on Gain output ratio at different components effectiveness for different percentages of brine recirculation (modified cycle).

CT ($ / yr ) = CF ($ / yr ) + PC ($ / yr ) + LC ($ / yr )

(18)

any given season. It is important to emphasize that effective condensation of pure water from the humidified air occurs at a low seawater temperature, leading to high productivity and low cost of freshwater production. Also, the effective condensation of freshwater equally leads to better heat recovery, which lowers the SEC of the system. It should be noted that water production cost varies weakly with seawater inlet temperature. Furthermore, the SEC and cost of freshwater production by the basic OAOW system is about three fold higher than that of the modified CWOA cycle. The impact of energy cost on the distilled water production cost for both the basic OAOW and modified CWOA cycles with the options of brine recirculation, is illustrated in Fig. 11. It is important to know how the cost of electricity moves the cost of desalted water since the price of

Now, the unit product cost (CP) can be written as,

CT ($ / yr ) ⎞ CP ($ / m3) = ⎛ 3/ day ) × 365(day / yr ) f × Product ( m ⎠ ⎝ ⎜

⎟

(19)

The results obtained from the cost analysis of the two HDH systems considered in the current study, are presented in Table 5 and Fig.11. The effect of variation in feed water inlet temperature on both the cost of freshwater production and the specific energy consumption (SEC) for the modified CWOA and basic OAOW cycles, are presented in Table 5. It is expected that seawater temperature changes over the year because of variations in the seasonal climatic changes (winter to summer) over the years. Therefore, it is important to estimate the cost of freshwater for 170

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Table 3 Comparison between various HDH cycles. Water-heated

Air-heated

MR

Modified CWssOA

OAOW

CAOW

CAOW

OAOW

0.45 0.5842 0.7184 0.8526 0.9868 1.121 1.255 1.389 1.524 1.658 1.792 1.926 2.061 2.195 2.329 2.463 2.597 2.732 2.866 3

0.3324 0.4009 0.4662 0.5284 0.5875 0.6437 0.6972 0.7041 0.7044 0.705 0.7058 0.7068 0.7078 0.7088 0.7099 0.711 0.7121 0.7132 0.7143 0.7153

0.2382 0.2938 0.3525 0.414 0.4777 0.543 0.5696 0.5648 0.5611 0.5581 0.5558 0.477 0.4066 0.357 0.3193 0.2894 0.265 0.2446 0.2273 0.2123

0.4301 0.4551 0.4829 0.514 0.5487 0.5875 0.5997 0.5878 0.5763 0.5653 0.5547 0.5445 0.4656 0.4001 0.3531 0.3172 0.2884 0.2648 0.245 0.2281

0.5866 0.5493 0.5143 0.4814 0.4505 0.4214 0.3941 0.3684 0.3441 0.3213 0.2997 0.2753 0.2302 0.1296 0.1163 0.1045 0.09409 0.08476 0.07639 0.06883

0.3768 0.332 0.3037 0.2841 0.2697 0.2585 0.2495 0.242 0.2357 0.2082 0.1579 0.1213 0.09317 0.07083 0.03899 0.02843 0.01909 0.01077 0.00334 −0.00334

Fig. 11. Influence of electricity cost on the fresh water cost.

Table 6 Comparison of the current systems with reverse osmosis (RO) desalination system. Cost of water production (0.71–0.83) $/m 0.70 €/m3 1.3 $/m3 1.39 $/m3 2.45 $/m3

Table 4 Capital investment cost for HDH plant [23,25]. Item description

Price (US $)

Control devices Packed bed humidifier Dehumidifier Finned tube coil heat exchangers Electric heater Pipes, fittings Water tanks Pumps and blowers Flowmeters Accessories Miscellaneous

80 133 70 120 48 35 260 345 230 33 573

3

2.37 $/m3 (0.12–0.13) $/m3 (4.10–6.55) $/m3 (0.79–2.25) $/m3

Desalination system

Authors

Ref

RO RO RO RO RO

Jamil et al. Romero et al. Fiorenza et al. Wade El-Emam and Dincer Darwish et al. Jamil et al. Present study Present study

[26] [27] [28] [29] [30]

RO HDH-RO Basic OAOW HDH cycle Modified CWOA HDH cycle

[31] [32] – –

competitive with RO desalination plant when small-scale water production is a priority. 5. Concluding remarks An experimental and thermodynamic analysis of basic open-air open-water (OAOW) and the modified closed-water open-air (CWOA) HDH desalination systems has been performed. The following significant conclusions are drawn from this study:

Table 5 Effects of increasing inlet water temperature on water production cost of HDH plant. Feed water temperature (°C)

18 20 22 24 26 28

Modified CWOA

Basic OAOW

SEC (kWh/ m3)

Water production cost ($/m3)

SEC (kWh/ m3)

Water production cost ($/m3)

17.53 20.23 24.5 28.2 33.4 38.6

2.083 2.186 2.31 2.461 2.647 2.881

55.2 63.6 69.5 81.3 97.7 124.7

6.726 6.608 6.489 6.365 6.234 6.088

• A theoretical model has been validated against the experimental • •

electricity varies from one location to another. As expected, an increase in the cost of electricity increases the cost of freshwater production for both the cycles. However, it is noted that the cost of water production by the modified CWOA cycle has been reduced, considerably, when compared to that of basic OAOW cycle. This is mainly due to energy recovered from the brine recirculation, which shows that energy cost is one of the most important cost factors in a desalination plant. Table 6 presents a unit product cost comparison between the current and reverse osmosis desalination systems. It is evident from the evaluated results that the cost of freshwater production from the basic OAOW HDH process is higher than the RO plant. However, the cost of freshwater production from modified CWAO HDH system can be very

• • • 171

data. The model was found to be in a good agreement with the experimental results, it was found that the maximum percentage error from the model is within 5% of the experimental data. The limits of humidifier and dehumidifier effectiveness have been defined based on the temperatures of brine recirculation and the make-up water. GOR of the system increases with MR. However, optimum MR exists where a further increase in MR leads to a reduction in the system GOR. The system GOR increases as the components effectiveness increases, which is mainly due to the better evaporation and condensation processes. However, the dehumidifier effectiveness was found to be more influential compared to the humidifier effectiveness. The behavior as well as the pattern of the system at 95% and 90% rejected brine recirculation is very similar to that of 100% (the modified cycle). However, from 80% to 10% rejected brine recirculation, the system mimic that of basic cycle, because the effect of makeup starts to outplay the effect of recirculated brine. For cases outside the limits of components effectiveness (where mixing is not justifiable), the point of intersection exists, which is an

Desalination 436 (2018) 161–175

S.M. Zubair et al.

• • •

production.

indication that the brine recirculation has no influence on GOR, because, a sort of balancing occurs and the system becomes insensitive to the rejected brine recirculation. The point of intersection moved from higher-to-lower MR as the dehumidifier effectiveness decreases. This point marks the region of the dominance of basic cycle over the modified cycle. There is a weak relationship between the product cost and inlet water temperature of seawater. Cost of electricity greatly influences the cost of freshwater

• The product cost calculated by current analysis for basic OAOW

HDH cycle and modified CWOA HDH cycle is 4.1 to 6.55 $/m3 and 0.79 to 2.25 $/m3, respectively.

Acknowledgements The authors acknowledge the support provided by King Fahd University of Petroleum & Minerals through the project IN151001.

Appendix A. Uncertainty analysis Table 1A Uncertainty values for the effect of changing heat input at MR = 2.27. Q (kW)

MR

εhum

εdeh

GOR (experimental)

5.6 4.4 3.2

2.27 ± 0.11 2.27 ± 0.11 2.27 ± 0.11

0.41 ± 0.003 0.44 ± 0.003 0.56 ± 0.004

0.81 ± 0.013 0.81 ± 0.015 0.85 ± 0.018

0.37 ± 0.003 0.40 ± 0.004 0.28 ± 0.005

Table 2A Uncertainty values for the effect of changing heat input at MR = 1.36. Q (kW)

MR

εhum

εdeh

GOR (experimental)

5.6 4.4 3.2

1.36 ± 0.07 1.36 ± 0.07 1.36 ± 0.07

0.54 ± 0.004 0.55 ± 0.004 0.57 ± 0.004

0.78 ± 0.015 0.83 ± 0.015 0.78 ± 0.025

0.33 ± 0.003 0.32 ± 0.004 0.23 ± 0.005

Table 3A Uncertainty values for the effect of varying air mass flow rate. Q (kW)

MR

εhum

εdeh

GOR (experimental)

5.6 5.6 5.6

2.27 ± 0.11 1.89 ± 0.10 1.56 ± 0.08

0.38 ± 0.002 0.41 ± 0.003 0.53 ± 0.003

0.77 ± 0.016 0.79 ± 0.018 0.85 ± 0.013

0.35 ± 0.003 0.28 ± 0.003 0.24 ± 0.003

Appendix B. Limits of components effectiveness Table B1 Components effectiveness valid for recirculation system at MR = 1.0. MR

ɛdeh

ɛhum

Tw2 (°C)

Tw4 (°C)

Observation

1 1 1 1 1 1 1 1 1 1 1 1 1 1

0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.7 0.7 0.7 0.8 0.8 0.85 0.85

0.40 0.47 0.53 0.60 0.40 0.47 0.53 0.40 0.47 0.53 0.40 0.47 0.40 0.47

24 25 26 27 25 26 28 26 28 29 27 29 28 30

31 30 29 28 32 31 30 32 32 31 33 32 33 33

MR = 1, ɛdeh = 0.5, 0.4 < ɛhum < 0.6

172

MR = 1, ɛdeh = 0.6, 0.4 < ɛhum < 0.53

MR = 1, ɛdeh = 0.7, 0.4 < ɛhum < 0.53

MR = 1, ɛdeh = 0.8, 0.4 < ɛhum < 0.47 MR = 1, ɛdeh = 0.85, 0.4 < ɛhum < 0.47

Desalination 436 (2018) 161–175

S.M. Zubair et al.

Table B2 Components effectiveness valid for recirculation system at MR = 1.5. MR

ɛdeh

ɛhum

Tw2 (°C)

Tw4 (°C)

Observation

1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.7 0.7 0.7 0.8 0.8 0.85 0.85

0.45 0.47 0.53 0.60 0.67 0.40 0.47 0.53 0.60 0.40 0.47 0.53 0.40 0.47 0.40 0.47

24 24 25 26 28 24 26 27 29 25 27 29 26 29 27 30

32 32 31 30 28 33 32 31 30 33 33 32 34 33 34 33

MR = 1.5, ɛdeh = 0.5, 0.45 < ɛhum < 0.67

MR = 1.5, ɛdeh = 0.6, 0.4 < ɛhum < 0.6

MR = 1.5, ɛdeh = 0.7, 0.4 < ɛhum < 0.53

MR = 1.5, ɛdeh = 0.8, 0.4 < ɛhum < 0.47 MR = 1.5, ɛdeh = 0.85, 0.4 < ɛhum < 0.47

Table B3 Components effectiveness valid for recirculation system at MR°=°2.0. MR

ɛdeh

ɛhum

Tw2 (°C)

Tw4 (°C)

Observation

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.7 0.7 0.7 0.7 0.7 0.7 0.8 0.8 0.8 0.8 0.8

0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.40 0.47 0.53 0.60 0.67 0.73 0.40 0.47 0.53 0.60 0.67

23 23 24 24 25 26 27 27 23 24 25 26 26 28 29 24 25 26 27 28 30 24 26 27 29 31

34 33 32 32 31 30 30 29 34 33 33 32 32 31 30 34 34 33 33 32 31 35 34 34 33 33

MR = 2, ɛdeh = 0.5, 0.4 < ɛhum < 0.86

MR = 2, ɛdeh = 0.6, 0.4 < ɛhum < 0.8

MR = 2, ɛdeh = 0.7, 0.4 < ɛhum < 0.73

MR = 2, ɛdeh = 0.8, 0.4 < ɛhum < 0.67

Table B4 Components effectiveness valid for recirculation system at MR = 2.5. MR

ɛdeh

ɛhum

Tw2 (°C)

Tw4 (°C)

Observation

2.5 2.5 2.5 2.5

0.5 0.5 0.5 0.5

0.40 0.47 0.53 0.60

22 23 23 24

34 34 33 33

MR = 2.5, ɛdeh = 0.5, 0.4 < ɛhum < 1

173

Desalination 436 (2018) 161–175

S.M. Zubair et al.

2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5

0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.8 0.8 0.8 0.8 0.8 0.8 0.8

0.67 0.73 0.80 0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.40 0.47 0.53 0.60 0.67 0.73 0.80

24 24 25 25 26 27 23 23 24 24 25 25 26 27 28 29 23 24 24 25 26 27 28 29 24 24 25 26 27 29 30

33 32 32 31 30 30 34 34 34 33 33 33 32 31 31 30 35 34 34 34 33 33 33 32 35 35 35 34 34 34 33

MR = 2.5, ɛdeh = 0.6, 0.4 < ɛhum < 1

MR = 2.5, ɛdeh = 0.7, 0.4 < ɛhum < 0.87

MR = 2.5, ɛdeh = 0.8, 0.4 < ɛhum < 1

Table B5 Components effectiveness valid for recirculation system at MR = 3. MR

ɛdeh

ɛhum

Tw2 (°C)

Tw4 (°C)

Observation

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.7 0.7 0.7 0.7 0.7 0.7 0.7

0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80

22 22 23 23 23 24 24 24 25 25 22 23 23 24 24 24 25 25 26 27 23 23 24 24 25 25 26

35 34 34 34 33 33 33 32 32 31 35 35 34 34 34 33 33 33 32 32 35 35 35 34 34 34 34

MR = 3, ɛdeh = 0.5, 0.4 < ɛhum < 1

174

MR = 3, ɛdeh = 0.6, 0.4 < ɛhum < 1

MR = 3, ɛdeh = 0.7, 0.4 < ɛhum < 1

Desalination 436 (2018) 161–175

S.M. Zubair et al.

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

0.7 0.7 0.7 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85

0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.93 1.00 0.40 0.47 0.53 0.60 0.67 0.73 0.80 0.87 0.93

27 28 29 23 24 24 25 26 26 27 28 30 32 23 24 24 25 26 27 28 29 31

33 33 32 35 35 35 35 35 34 34 34 33 33 35 35 35 35 35 35 34 34 34

References [17] [1] G.P. Narayan, M.H. Sharqawy, E.K. Summers, J.H. Lienhard V, S.M. Zubair, M.A. Antar, The potential of solar-driven humidification-dehumidification desalination for small-scale decentralized water production, Renew. Sust. Energ. Rev. 14 (4) (2010) 1187–1201. [2] J.H. Lienhard V, M.A. Antar, A. Bilton, J. Blanco, G. Zaragoza, Solar desalination, book chapter 9, Annual Review of Heat Transfer, Begell House, Inc., New York, NY, 2012, pp. 277–347. [3] A. Giwa, N. Akther, A. Al Housani, S. Haris, S.H. Hasan, Recent advances in humidification dehumidification (HDH) desalination processes: improved designs and productivity, Renew. Sust. Energ. Rev. 57 (2016) 929–944. [4] G.P. Narayan, R.K. McGovern, G.P. Thiel, J.A. Miller, J.H. Lienhard V, M.H. Sharqawy, S.M. Zubair, M.A. Antar, Status of Humidification Dehumidification Desalination, IDA World Congr. Desalin, Water Reuse, 2011. [5] N. Niroomand, M. Zamen, M. Amidpour, Theoretical investigation of using a direct contact dehumidifier in humidification–dehumidification desalination unit based on an open air cycle, Desalin. Water Treat. 54 (2) (Jan 2014) 305–315. [6] J.F. Klausner, Y. Li, M. Darwish, R. Mei, Innovative diffusion driven desalination process, J. Energy Resour. Technol. 126 (2004) 219–225. [7] B. Dawoud, Y.H. Zurigat, B. Klitzing, T. Aldoss, G. Theodoridis, On the possible techniques to cool the condenser of seawater greenhouses, Desalination 195 (1–3) (2006) 119–140. [8] H.M. Ettouney, Design and analysis of humidification dehumidification desalination process, Desalination 183 (3) (2005) 341–352. [9] G.P. Narayan, M.H. Sharqawy, J.H. Lienhard V, S.M. Zubair, Thermodynamic analysis of humidification-dehumidification desalination cycles, Desalin. Water Treat. 16 (2010) 339–353. [10] M.H. Sharqawy, M.A. Antar, S.M. Zubair, A.M. Elbashir, Optimum thermal design of humidification-dehumidification desalination systems, Desalination 349 (Sep 2014) 10–21. [11] A. Aburub, M. Aliyu, D.U. Lawal, M.A. Antar, Experimental investigations of the performance of a cross-flow humidification-dehumidification desalination system, Twentieth International Water Technology Conference, IWTC20, Hurghada, 18–20 May, 2017. [12] A. Aburub, M. Aliyu, D.U. Lawal, M.A. Antar, Experimental investigations of a cross-flow humidification dehumidification desalination system, IWTJ. 7 (3) (2017) 198–208. [13] T. Brendel, Solare Meewasserental sungsanlagen mit mehrstufiger verdungtung (PhD thesis), Ruhr University Bochum, 2003. [14] T. Brendel, Process to Distil and Desalinate Water in Contra-flow Evaporation Humidifier Unit With Progressive Removal of Evaporated Fluid, (2003) German Patent #DE10215079 (A1). [15] R.K. McGovern, G.P. Thiel, G.P. Narayan, S.M. Zubair, J.H. Lienhard V, Performance limits of zero and single extraction humidification-dehumidification desalination systems, Appl. Energy 102 (2013) 1081–1090. [16] G.P. Narayan, J.H. Lienhard V, S.M. Zubair, Entropy generation minimization of

[18]

[19]

[20]

[21]

[22]

[23]

[24]

[25] [26]

[27] [28] [29] [30]

[31]

[32]

175

MR = 3, ɛdeh = 0.8, 0.4 < ɛhum < 1

MR = 3, ɛdeh = 0.85, 0.4 < ɛhum < 1

combined heat and mass transfer devices, Int. J. Therm. Sci. 49 (10) (2010) 2057–2066. K.H. Mistry, J.H. Lienhard V, S.M. Zubair, Effect of entropy generation on the performance of humidification-dehumidification desalination cycles, Int. J. Therm. Sci. 49 (9) (2010) 1837–1847. G.P. Narayan, K.M. Chehayeb, R.K. McGovern, G.P. Thiel, S.M. Zubair, J.H. Lienhard V, Thermodynamic balancing of the humidification-dehumidification desalination system by mass extraction and injection, Int. J. Heat Mass Transf. 57 (2) (Feb 2013) 756–770. G.P. Narayan, M.G. St. John, S.M. Zubair, J.H. Lienhard V, Thermal design of the humidification-dehumidification desalination system: an experimental investigation, Int. J. Heat Mass Transf. 58 (1–2) (Mar. 2013) 740–748. K.M. Chehayeb, G.P. Narayan, S.M. Zubair, J.H. Lienhard V, Use of multiple extractions and injections to thermodynamically balance the humidification-dehumidification desalination system, Int. J. Heat Mass Transf. 68 (Jan 2014) 422–434. M.H. Sharqawy, J.H. Lienhard V, S.M. Zubair, Thermophysical properties of seawater: a review of existing correlations and data, Desalin. Water Treat. 16 (1–3) (Apr 2010) 354–380. A. Eslamimanesh, M.S. Hatamipour, Economical study of a small-scale direct contact humidification-dehumidification desalination plant, Desalination 250 (2010) 203–207. A.E. Kabeel, T.A. Elmaaty, E.M.S. El-Said, Economic analysis of a small-scale hybrid air HDH-SSF (humidification and dehumidification-water flashing evaporation) desalination plant, Energy 53 (2013) 306–311. D. Lawal, M. Antar, A. Khalifa, S. Zubair, F. Al-Sulaiman, Humidification-dehumidification desalination system operated by a heat pump, Energy Convers. Manag. 161 (2018) 128–140. H.T. El-Dessouky, H.M. Ettouney, Fundamentals of salt-water desalination, 1st ed., ELSEVIER, 2002, p. 514. M.A. Jamil, B.A. Qureshi, S.M. Zubair, Exergo-economic analysis of a seawater reverse osmosis desalination plant with various retrofit options, Desalination 401 (2017) 88–98. V. Romero-Ternero, L. Garcia-Rodriguez, C. Gomez-Camacho, Thermoeconomic analysis of a seawater reverse osmosis plant, Desalination 181 (2005) 43–59. G. Fiorenza, V.K. Sharma, G. Braccio, Techno-economic evaluation of a solar powered water desalination plant, Energy Convers. Manag. 44 (2003) 2217–2240. N.M. Wade, Technical and economic evaluation of distillation and reverse osmosis desalination processes, Desalination 93 (1993) 343–363. R.S. El-Emam, I. Dincer, Thermodynamic and thermoeconomic analyses of seawater reverse osmosis desalination plant with energy recovery, Energy 64 (2014) 154–163. M.A. Darwish, M.A. Jawad, G.S. Aly, Comparison between small capacity mechanical vapor compression (MVC) and reverse osmosis (RO) desalting plants, Desalination 78 (1990) 313–326. M.A. Jamil, S.M. Elmutasim, S.M. Zubair, Exergo-economic analysis of a hybrid humidification dehumidification reverse osmosis (HDH-RO) system operating under different retrofits, Energy Convers. Manag. 158 (2018) 286–297.