Falling-film heat exchangers used in desalination systems: A review

Dai, Zhaoxin; Zhang, Yuheng; Wang, Xin Wei; Nawaz, Kashif; Jacobi, Anthony M.

doi:10.1016/j.ijheatmasstransfer.2021.122407

Cited by 32 publications

(7 citation statements)

References 133 publications

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“…It must be remembered that the evaporation rate is proportional to the free surface area of the evaporating liquid. Additionally, according to Dai et al [27], the thickness and flow mode of a falling film have a significant impact on the overall heat transfer coefficient between the tube and the falling film. Thus, the possibility cannot be excluded that the spray angle affects the falling film's thickness and flow mode, which results in an improved heat transfer coefficient, a faster evaporator, and greater cooling capacity.…”

Section: The Effect Of Spray Angle On Adsorption-chiller Performancementioning

confidence: 99%

The Effect of Nozzle Configuration on Adsorption-Chiller Performance

Kalawa,

Sztekler,

Kozaczuk

et al. 2024

Energies

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Broadly defined climate protection is a powerful incentive in the search for environmentally friendly refrigeration technologies. Adsorption chillers are considered to be one such technology; however, their main disadvantages include a low cooling capacity, a low energy efficiency ratio (EER), and cyclic operation. Thus, a great deal of effort is being put into improving adsorption-chiller performance. In this paper, the influence of the spray angle, the number of nozzles, and the water flow rate through the nozzles on adsorption-chiller performance was investigated. Adsorption-chiller performance was investigated mainly in terms of the cooling capacity (CC), the energy efficiency ratio (EER), and the specific cooling power (SCP). The results indicated that the chiller’s cooling capacity increased from about 210 W to 316 W and that the EER increased from 0.110 to 0.167 when the spray angle of the nozzles was increased from 90° to 120°. It was also reported that increasing the flow rate of water through the nozzles did not improve the average cooling capacity or the other performance parameters but resulted in more stable operation of the chiller. Additionally, using six nozzles instead of three improved the average cooling capacity and EER tenfold.

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Section: The Effect Of Spray Angle On Adsorption-chiller Performancementioning

confidence: 99%

The Effect of Nozzle Configuration on Adsorption-Chiller Performance

Kalawa,

Sztekler,

Kozaczuk

et al. 2024

Energies

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“…This finding indicates that the primary impediment to the overall efficiency of solar thermal desalination systems is the low efficiency of the condensation component. The utilization of various materials for freshwater collection in condensation components, particularly conventional transparent cover plate designs, is constrained by factors such as limited light transmission and the presence of noncondensing gas, which obstruct the crucial improvement of overall performance. − Compared with traditional glass cover plates in noncondensing situations, the utilization of gel materials for air freshwater capture in low relative humidity conditions − has demonstrated superior performance. Thermosensitive hydrogels , typically incorporate both hydrophobic and hydrophilic groups within their own network.…”

Section: Introductionmentioning

confidence: 99%

Deswelling Mechanisms of PNIPAM Grafted in Nanochannels: A Molecular Dynamics Simulation Study

Chen,

Niu,

Gao

et al. 2024

Langmuir

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Porous thermosensitive hydrogels exhibit a more flexible strategy for freshwater capture compared to conventional hydrogels. This study employs molecular dynamics (MD) simulation to investigate the deswelling behavior of poly(Nisopropylacrylamide) (PNIPAM) grafted within the nanochannel, aiming to elucidate the deswelling elimination process at various temperatures. Notably, a distinct phase separation is observed at specific temperatures above the lower solution temperature (LCST). Furthermore, this study takes the effect of heat flux into account, wherein distinct heat fluxes lead to varying levels of phase separation between water and the polymer. Specifically, the number of hydrogen bonds, volume of polymer chains, and density distribution of water molecules are statistically analyzed to reveal the mechanism of phase separation in a thermosensitive hydrogel. These findings provide insight into the accelerated deswelling kinetics of the PNIPAM polymer chain, which has guiding significance for the field of water harvesting by the enhancement of the water release capacity in thermosensitive hydrogels.

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“…The liquid falling film thermal desalination process has been numerically and experimentally studied by researchers who have mainly investigated the the impacts of inlet Reynolds number, fluid properties, and inlet liquid temperature for the case of liquid film flow over a horizontal tube surface [14][15][16][17][18]. A complete literature review of falling film evaporation in desalination systems was performed by Dai et al [19]. The study of thermal desalination inside vertical channels and tubes is limited.…”

Section: Introductionmentioning

confidence: 99%

A Two-Phase Sharp-Interface Numerical Model of Falling Film Thermal Desalination in a Vertical Channel

Tohidi,

Ormiston

2024

Preprint

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A two-dimensional, sharp-interface two-phase laminar flow numerical model for evaporation from a saltwater falling liquid film with a co-current humid air flow on the interior of a parallel plate vertical channel is presented. The elliptic governing equations in both phases are solved simultaneously in an implicit, fully coupled approach. The liquid-gas interface is tracked precisely on an automatically adjusted non-orthogonal structured mesh. The basis of the evaporation model is validated for pure water falling film evaporation. A parametric study of evaporation from a saltwater falling film is presented. The study varies the inlet salinity of the film, the inlet liquid Reynolds number, the wall heat flux, and the air relative humidity. The effects of these variations on quantities such as the evaporation rate, the axial velocity, the salinity in the film, and the temperature are presented. The results demonstrate the capablity of the new model to predict the details of falling film thermal desalination.

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Falling-film heat exchangers used in desalination systems: A review

Cited by 32 publications

References 133 publications

The Effect of Nozzle Configuration on Adsorption-Chiller Performance

The Effect of Nozzle Configuration on Adsorption-Chiller Performance

Deswelling Mechanisms of PNIPAM Grafted in Nanochannels: A Molecular Dynamics Simulation Study

A Two-Phase Sharp-Interface Numerical Model of Falling Film Thermal Desalination in a Vertical Channel

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