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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Damage, sources of heat exchangers Damkohler number: Damping: Davis and Anderson criterion, for onset of nucleate boiling, Decal, heat transfer medium, Decane: 1-Decanol: 1-Decene: Degradation temperature, of polymers, Demisters, wire mesh, for multistage flash evaporators,
Flash Desalination Processes design parameters, materials for, models and correlations for, performance of,
Dengler and Addoms correlation, for forced convective heat transfer in two-phase flow, Density: Deposition of droplets in annular flow Deposition in fouling, Desalination plants: Desuperheaters for use in association with evaporators, Developing flow in ducts: Dew-poin corrosion, Diathermanous fluid, 1,1-Dibromoethane: Dibromomethane: 1,2-Dibromotetrafluoroethane (Refrigerant 114B2): Dibutylamine: Dibutyl ether: Dichloroacetic acid: o-Dichlorobenzene: Dichlorodifluoromethane (see Refrigerant 12) 1,1-Dichloroethane (Refrigerant 150a): 1,2-Dichloroethane (Refrigerant 150): 1,1-Dichloroethylene: cis-1,2-Dichloroethylene: trans-1,2-Dichloroethylene: Dichlorofluoromethane (see Refrigerant 21) Dichloromethane (Refrigerant 30): 1,2-Dichlorotetrafluoroethane (Refrigerant 114) 1,2,3-Dichlorotrifluoroethane (Refrigerant 123) Dielectric constant, of water, Diethylamine: n,n-Diethylaniline: Diethylene glycol: Diethyl ether: Diethyl ketone: Diethylsulfide: Differential condensation: Differential formulations for nonisothermal gas radiation, Differential resistance term in heat exchanger design, Differential vector operators in heat conduction, Diffraction models for radiative heat transfer from surfaces, Diffuse surfaces, radiative heat transfer between, Diffuse wall passages, radiative heat transfer in, Diffusers, single-phase flow and pressure drop in, Diffusion, in multi-component condensation, n,n-Diffusion coefficients: 1,1-Difluoroethane (Refrigerant 152a): Difluoromethane (Refrigerant 32): Diiodomethane: Diisobutylamine: Diisopropylamine: Diisopropylether: Dimensional analysis: Dimensionless groups: Dimethylacetylene: Dimethylamine: Dimethylaniline: 2,2-Dimethylbutane: 2,3-Dimethylbutane: 1,1-Dimethylcyclopentane: Dimethylether: Dimethylketone: 2,2-Dimethylpropane (neopentane): Dimethylsulfide: Dimpled surfaces, heat exchangers with, 1,4-Dioxane: Diphenyl: Diphenylamine: Diphenylether: Diphenylmethane: Dipropyl ether: Diisopropyl ether: Dipropyl ketone: Direct contact heat exchangers Direct contact heat transfer, Direct numerical simulation, of turbulence, Dirichlet boundary condition, finite difference method, Dished heads: Discretization in numerical analysis: Disk-and-doughnut baffled heat exchangers, Disks, free convective heat transfer from inclined, Dispersants, for fouling control, Dispersed flow (liquid-liquid), Dissipation of turbulent energy, Distillation: Distribution: Dittus-Boelter equation, for single-phase forced convective heat transfer, Dividing flow, loss coefficients in, Dodecane: 1-Dodecene: Donohue method, for shell-side heat transfer in shell-and-tube heat exchangers, Double-pipe heat exchangers: Double segmental baffled heat exchangers, Downward facing surfaces, free convective heat transfer from, Downward flow in vertical tubes, flow patterns in gas/liquid, Dowtherm A: Dowtherm J: Dowtherms, as heat transfer media, Drag coefficient: Drag force: Drag reduction, Drainage, of condensate, Dreitser, G, Drift flux model for two-phase flows, Drogemuller, P, Droplets: Dropwise condensation Dry wall desuperheating (in condensation), Dryers: Drying loft, Drying rates, prediction of, Dryout: Ducts, single-phase fluid flow and pressure drop in, Duplex stainless steels, Durand correlation for heterogeneous conveyance in solid/liquid flow, Dynamically stable foam, Dyphyl, heat transfer media, Dzyubenko, B,

Index

HEDH
A B C D
Damage, sources of heat exchangers Damkohler number: Damping: Davis and Anderson criterion, for onset of nucleate boiling, Decal, heat transfer medium, Decane: 1-Decanol: 1-Decene: Degradation temperature, of polymers, Demisters, wire mesh, for multistage flash evaporators,
Flash Desalination Processes design parameters, materials for, models and correlations for, performance of,
Dengler and Addoms correlation, for forced convective heat transfer in two-phase flow, Density: Deposition of droplets in annular flow Deposition in fouling, Desalination plants: Desuperheaters for use in association with evaporators, Developing flow in ducts: Dew-poin corrosion, Diathermanous fluid, 1,1-Dibromoethane: Dibromomethane: 1,2-Dibromotetrafluoroethane (Refrigerant 114B2): Dibutylamine: Dibutyl ether: Dichloroacetic acid: o-Dichlorobenzene: Dichlorodifluoromethane (see Refrigerant 12) 1,1-Dichloroethane (Refrigerant 150a): 1,2-Dichloroethane (Refrigerant 150): 1,1-Dichloroethylene: cis-1,2-Dichloroethylene: trans-1,2-Dichloroethylene: Dichlorofluoromethane (see Refrigerant 21) Dichloromethane (Refrigerant 30): 1,2-Dichlorotetrafluoroethane (Refrigerant 114) 1,2,3-Dichlorotrifluoroethane (Refrigerant 123) Dielectric constant, of water, Diethylamine: n,n-Diethylaniline: Diethylene glycol: Diethyl ether: Diethyl ketone: Diethylsulfide: Differential condensation: Differential formulations for nonisothermal gas radiation, Differential resistance term in heat exchanger design, Differential vector operators in heat conduction, Diffraction models for radiative heat transfer from surfaces, Diffuse surfaces, radiative heat transfer between, Diffuse wall passages, radiative heat transfer in, Diffusers, single-phase flow and pressure drop in, Diffusion, in multi-component condensation, n,n-Diffusion coefficients: 1,1-Difluoroethane (Refrigerant 152a): Difluoromethane (Refrigerant 32): Diiodomethane: Diisobutylamine: Diisopropylamine: Diisopropylether: Dimensional analysis: Dimensionless groups: Dimethylacetylene: Dimethylamine: Dimethylaniline: 2,2-Dimethylbutane: 2,3-Dimethylbutane: 1,1-Dimethylcyclopentane: Dimethylether: Dimethylketone: 2,2-Dimethylpropane (neopentane): Dimethylsulfide: Dimpled surfaces, heat exchangers with, 1,4-Dioxane: Diphenyl: Diphenylamine: Diphenylether: Diphenylmethane: Dipropyl ether: Diisopropyl ether: Dipropyl ketone: Direct contact heat exchangers Direct contact heat transfer, Direct numerical simulation, of turbulence, Dirichlet boundary condition, finite difference method, Dished heads: Discretization in numerical analysis: Disk-and-doughnut baffled heat exchangers, Disks, free convective heat transfer from inclined, Dispersants, for fouling control, Dispersed flow (liquid-liquid), Dissipation of turbulent energy, Distillation: Distribution: Dittus-Boelter equation, for single-phase forced convective heat transfer, Dividing flow, loss coefficients in, Dodecane: 1-Dodecene: Donohue method, for shell-side heat transfer in shell-and-tube heat exchangers, Double-pipe heat exchangers: Double segmental baffled heat exchangers, Downward facing surfaces, free convective heat transfer from, Downward flow in vertical tubes, flow patterns in gas/liquid, Dowtherm A: Dowtherm J: Dowtherms, as heat transfer media, Drag coefficient: Drag force: Drag reduction, Drainage, of condensate, Dreitser, G, Drift flux model for two-phase flows, Drogemuller, P, Droplets: Dropwise condensation Dry wall desuperheating (in condensation), Dryers: Drying loft, Drying rates, prediction of, Dryout: Ducts, single-phase fluid flow and pressure drop in, Duplex stainless steels, Durand correlation for heterogeneous conveyance in solid/liquid flow, Dynamically stable foam, Dyphyl, heat transfer media, Dzyubenko, B,
E F G H I J K L M N O P Q R S T U V W X Y Z
D Demisters, wire mesh, for multistage flash evaporators,
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Flash Desalination Processes

DOI 10.1615/hedhme.a.000384

3.22 FLASH EVAPORATION
3.22.2 Flash desalination processes

H. El-Dessouky and H. Ettouney

On an industrial scale the flash desalination process has a multistage configuration for flash evaporation. The main elements of the process include the brine heater and the flashing stages. Other process units include the feed intake, brine disposal lines, deaerator, chemical dosing, pumping station, vacuum ejectors, and the control room. The most common industrial process is the multistage flashing process with brine circulation (MSF). On the other hand, the once through multistage flashing process (MSF-OT) is found on a very limited scale. Also, it should be noted that the single stage flashing system (SSF) combined with a brine heater is not used on industrial scale because of its low performance. However, discussion of the SSF process and development of a mathematical model for it are necessary to have better understanding of the more complex processes found in the multistage flashing systems.

The most characteristic feature of the flash desalination process is that vapor formation takes place within the liquid bulk instead of the surface of hot tubes. The hot brine is allowed to flow freely and flash in a series of chambers; this feature keeps the hot and concentrated brine from the inside or outside surfaces of heating tubes. This is a major advantage over the original and simple concept of thermal evaporation, where submerged tubes of heating steam are used to perform fresh water evaporation. The performance of submerged tubes was far from satisfactory, where salt scale is formed progressively on the outside surface of the tubes. The formed scale has a low thermal conductivity and acts as an insulating layer between the heating steam and the boiling seawater. Consequently, the evaporation rate is drastically reduced and cleaning becomes essential to restore the process efficiency.

Earlier designs of the flash desalination process were developed on commercial scale in the early 1950’s. Silver (1970) modified these earlier designs and devised the MSF process, where the number of flashing stages was much larger than the thermal performance ratio. The development optimized the system heat transfer area and the number of flashing stages. Since the establishment of the process in the late fifties, a huge amount of field experience has been accumulating in process technology, system design, construction practice, operation, and maintenance. Developments addressed several operational problems that include scale formation, foaming, fouling, and corrosion. The experience gained has led to use of inexpensive construction material capable of withstanding the harsh conditions at high seawater salinity. The MSF system does not include moving parts, other than conventional pumps. Construction of the MSF plants is simple and contains a small number of connections, which limits leakage problems and simplifies maintenance work. It is believed that the MSF system has remained the optimum choice for large capacity plants for desalination of seawater for the following reasons:

  • The conservative nature of the desalination owner.

  • The product is a strategic life-supporting element.

  • Extensive experience in construction and operation.

  • Process reliability.

  • Limited experience, small database, and unknown risks with new technologies.

Since inception, several developments have been achieved in system design and operation. These developments include the following:

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