WO2014004718A2 - Compact desalination or distillation system with integral spiral heat exchanger - Google Patents

Abstract

A vapor compression desalination or distillation system with a compact geometry that feature tripartite spiral fluidic pathways (60) that terminate a an evaporization zone within a plenum (63) internal to the spiral pathways inside of a housing. One side (66) of the zone receives sea water for distillation from one of the spiral pathways and ejects non-distilled water on the opposite side (68) in another spiral pathway. The heated central portion of the zone gives off vapor from the sea water that is collected in a shroud (73) that feeds radially inward ends of a compressor (71). Compressed vapor is ejected and collected from radially outward ends of the blades in a plenum (63), then fed as steam and condensate to an outflowing spiral pathway. The pathways are grouped in a tight spiral relation such that hot outflowing steam and condensate transfers heat to inflowing sea water in a heat exchange relation.

Description

Description

COMPACT DESALINATION OR DISTILLATION SYSTEM WITH INTEGRAL SPIRAL HEAT EXCHANGER

Technical Field

The invention relates to vapor-compression desalination and distillation and, more particularly, a compact device for vapor-compression of sea water o the like.

Background Art

Vapor compression desalination is a process where sea water, or the like, is evaporated by a source of heat and then fed to a compressor forming a stream of steam. The compressor increases both the pressure and temperature of the steam that is put into a pipe that passes through the sea water supply. Since the steam is hotter than the water supply, it gives up heat to the water as the steam is condensed. The outflow of the condensed steam is distilled water.

A typical small-scale vapor compression system of the prior art, with an integral heat exchanger, is illustrated in Fig. 1. Feed water enters the system via inflow pipe 11 to a conventional water heater 13. Heated water is dumped from water heater 13 to boiler chamber 15 having a heater unit 17 shown having an electrical heating element 19. Heated vapor 20 rises from the boiling water .21 toward hood 23 and to the interior of the radial vane compressor 25 where spinning blades apply centrifugal outward force to the vapor, compressing the vapor into a stream of steam that is released into the steam conduit 27. Compression of the vapor in the compressor raises both the pressure and the temperature of the vapor in the steam stream in conduit 27.. The steam in conduit 27 starts to condense as the conduit passes through the boiler chamber where the steam in conduit 27 gives up heat to water 21 in the boiler chamber 15 and gives up more heat to the water in the lower temperature water heater 13, finally emerging in fully condensed form as distilled water at distilled water outlet 29.

While small-scale vapor compression systems of the prior art, similar to the apparatus of Fig. 1 are in widespread use, the apparatus is larger than required for small installations, such as boats, small restaurants and homes. Such facilities often do not have distilled or clean water readily available, but instead have a source of sea water or the like, and requiring only modest amounts of distilled or clean water. An object of the invention was to devise a compact desalination apparatus.

Summary of Invention

The above object has been met with a desalination system that is a compact arrangement that features tripartite spiral fluidic pathways terminating in three manifolds including a first distilled water outflow manifold, a second seawater inflow manifold and a third non-distilled product manifold, such as non- distilled or brine water outflow. manifold. The

tripartite pathways refer to three tightly wound spiral fluidic pathways have a width that spans a distance between spaced apart side walls of a table top or small apparatus housing that could be a home appliance. The three pathways are adjacent to each other with a first pathway for outflowing distillate or brine, a second pathway for inflowing sea water and a third pathway for outflowing non-distillate. The housing has an interior structure with a radially outer plenum portion where the tripartite spiral fluidic pathways reside. The housing also has a radially inner plenum portion having an evaporation zone, such as a shelf, supporting a

compressor above the sea water vaporization zone where electrical heaters cause vaporizing of the sea water.

Rising vapor from the evaporation zone is collected by a shroud or hood feeding radially inward blade ends of the compressor .

The evaporation zone receives inflowing sea water from an inward end of the central spiral pathway, heated by the electrical heater associated with the zone. As the sea water boils, vapor is collected in a shroud and fed to the compressor. Concentrated seawater that does not give off vapor is non-distilled product or brine that is removed from the shelf by gravity flow or a pump into the outer spiral pathway toward a plenum associated with pressure removal from the spiral pathway. The vapor entering the compressor undergoes centrifugal compression and exits the compressor as steam that is directed into the inner spiral pathway in a lower portion of the plenum. Since the inner spiral pathway is adjacent to the inflowing sea water in the central spiral pathway, the steam in the inner spiral pathway is cooled and condenses, while the inflowing sea water is heated. The cooled and condensed steam flows into the distilled water product manifold.

The system is improved over current systems in that much less heat is lost to the flow of outgoing fluids. This is a result of the configuration of the system where there is efficient heat transfer from the outgoing fluids to the incoming fluids.. Further, the system has less thermal resistance in the conduction of heat from the vaporization to the condensation sections of the system. Evaporation takes place at sub-atmospheric pressure.

A significant advantage of the vaporization and

condensation section of the present system is the low thermal resistance of the heat conduction from the vaporization section of the system to the condensation areas. The specific advantage is a function of the small thickness of the material separating these two regions and the relatively large surface area for the conduction to occur and the overall compact structure of the unit. A further advantage is the vaporization and condensation section of the system is located within the heat transfer subsystem that transfers heat from the incoming liquids to the outgoing liquids. By having large aspect ratios of the length of the flow paths to the diameter of the system, the amount of heat transfer is further increased. A further advantage of the heat transfer system is the very low difference between the temperatures of the inlet fluids with that of the outlet fluids at important locations. Radiation and conduction heat loss of this subsystem is also minimal. As with the vaporization and condensation subsection, the longer the system is in relationship to the diameter, performance is improved. A further advantage of the present system is that the vaporization and condensation subsystem is located within the inlet and outlet heat transfer section. With this configuration the cost, maintenance and heat losses associated with having them in separate locations are eliminated.

Description of the Drawings

Fig. 1 is a plan view of a to vapor-compression desalination system of the prior art. Fig. 2 is a perspective view of the outside of a housing for the vapor-compression system of the present invention .

Fig- 3 is a bottom perspective view of the housing of Fig. 2. Fig. 4 is a lower internal perspective view of a vapor-compression system of the invention within the housing shown in Fig. 3 with a side wall removed. Fig. 5 is a side elevation plan view of the apparatus of Fig. 4 from an opposite side with the opposite side wall removed.

Fig. 6 is a magnified detail of a lower portion of the view of Fig. 5.

Fig. 7 is a right side detail view of the central portion of the apparatus of Fig. 5 showing the shelf interface with tripartite spiral pathways.

Fig. 8 is a left side detail view of the central portion of the apparatus of Fig. 5 showing the shelf interface with tripartite spiral pathways. Fig. 9 is an upper internal perspective view of the apparatus shown in Fig. 4.

Detailed Description

With reference to Fig. 2, the desalination system of the invention has a housing 31 with insulated side walls 33 and 35 that have external insulation panels. The side walls and insulation panels are spaced apart by a distance that can preferably range from 10 inches to 40 inches approximately, but could be wider.

The insulated side walls 33 and 35 are generally round in shape, with the space between the walls bounded by the outer spiral wall 37. The outer spiral wall 37 forms a portion of tripartite spiral pathways discussed below. Insulation on the side walls serves to reduce the heat transfer from the side walls to the outside environment. The side wall 33 covers an end of a lateral side of outer spiral wall 37. The side wall 35 covers the opposite lateral side of outer spiral wall 37. Thus, each of the side walls 33 and 35 is covered by a panel of insulation. Near the center of the side wall 33, a hole allows for a blower motor 39 to extend through the side wall. This blower motor 39 turns a coaxial drive shaft, not shown, of a compressor that is internal to the housing 31. At the bottom right side of Fig. 2 the outlet flat wall 41, part of the tripartite spiral pathways, can be seen extending from the lower portion of the outer spiral wall 37.

Referring to Fig. 3, the outer spiral wall 37 extends from the top of the desalination system around to the bottom of the system where it mates to one of three manifolds, namely the distilled water outlet first manifold 50. The distilled water outlet manifold 50 has the outlet fitting 51 where the distilled product of the desalination system exits. Adjacent to the first outlet manifold 50 is the second manifold 52 that serves as an inflow manifold for sea water, or the like (another fluid for distillation), coming into the system through the inlet fitting 54. The inlet fitting 54 is fastened to. the inlet manifold 52. Further, adjacent to the inlet manifold 52 is the second outlet manifold 53 where the concentrated non-distilled product or brine of the desalination system exits. Further, the second outlet fitting 55 is fastened to the second outlet manifold 53 where the concentrated non-distilled product or brine of the process is discharged._. Typically pumps, not shown, or gravity would be used to drive fluids into and out of the system. Pumps would be used ±o drive fluids through the tripartite spiral pathways described below. The inlet fluid may be filtered or otherwise pretreated before the fluid is pumped into the system through inlet fitting 54.

Referring to Fig. 4 the desalination system of Fig. 1 is shown with opposite side walls removed. The manifolds 50, 52 and 53 are each linked to tripartite spiral pathways formed by spiral walls that extend laterally between . opposite side walls. The spiral pathways thereby possess a wide lateral extent, namely the total distance between lateral side walls, but may have a height of only a few millimeters.. The spiral should have at least 5 complete loops, giving a high path length to path width aspect ratio.

As an example, the outlet flat wall 41,

previously described in Fig. 2, forms part of the second outlet manifold 53. The spiral pathway partly defined by flat wall 41, together with the elements along with the opposed side walls contain the concentrated non-distilled product or brine of the desalination system. The second spiral wall 30 is another member of the spiral pathway that constrains the concentrated non-distilled product or brine of the desalination system. For each of the three manifolds 50, 52 and 53 there is a corresponding spiral pathway such that there are tripartite fluidic pathways, one pathway for distilled product outflowing, one

adjacent pathway for inflowing sea water to be purified and one adjacent pathway for non-distilled product or brine outflowing. Walls are formed of thin self- supporting metal that is coiled like a spring where adjacent wall members do not touch each other but

maintain separation at generally uniform small distance due to spring memory. Small inert spacers may be placed within the spiral pathways to maintain uniform separation between spiral walls when the spiral pathways are

established. Figs. 4 and 5 show that with removal of the side walls, the housing shown in Fig. 1 has an interior structure that consists partly of a radially outer plenum portion 61 formed by the tripartite pathway structure 60 closed by an outer wall 58 between opposed sidewalls..

Another portion of the interior structure of the system consists of a radially inward, plenum portion 63 that is defined by the inward portion of the spiral. In other words, the spiral pathways extend inwardly less than half of the diameter of the housing, i.e. the largest spiral wall. Inward of the spiral pathways, an inward plenum portion 63 serves as a space for an evaporation zone, such as shelf 65, that receives inwardly flowing sea water, or fluid for distillation, from the middle spiral pathway that terminates near lip 66. The evaporation zone may be slightly canted so that there is slight downhill flow. Electrical heater coils 67 on the

underside of the shelf, will cause heating of incoming fluid and vaporization. The evaporation zone is made hotter near the center and below the radial blade

compressor 71. Fluid that does not vaporize or boil off is collected at the opposite end of the zone, near lip 68 where the heated brackish water or fluid flows into the inner spiral pathway, where it can be pumped out. The compressor has a shroud 73 that directs rising vapor being boiled from the zone into rotating vanes 75 of compressor 71 spinning about driven axis 77. The shroud has laterally outwardly extending side flanges 74 that close the vapor path over the zone and direct vapor into the shroud toward the compressor.

As explained above, a 'blower motor has a shaft that extends through walls of the system housing and is coaxial with, and joined to, driven axis 77 for rotary power transfer to the compressor. The shroud defines a low pressure side facing shelf 65 and has a high pressure side on the radially outward side of the vanes 75 where steam is formed by the increase in pressure and

temperature of the vapor by centrifugal force action of the compressor blades. One or more tunnels 81 through the shelf and the shroud flanges 74, allow the passage of steam into the lower plenum portion 64. Volumetric expansion of the steam into the lower plenum portion 64 causes some steam condensation and mixed condensate and steam entry into the outer spiral pathway at entry point 66. Since the entry point is at the bottom of the plenum, steam that has condensed into distilled water will enter the spiral pathway especially if a pump is attached to the spiral pathway creating a negative pressure pulling the condensate into the pathway. Thus steam, gaining thermal energy as well as pressure from the compressor, as well as distilled water., is in the outer spiral pathway with heat exchange to inflowing sea water in the central spiral pathway that, in turn, is adjacent to outflowing non-distilled product or brine. In this manner inflowing sea water is heated before it flows into the evaporation zone by the hot steam and distilled water that is contra-flowing in an adjacent spiral pathway. The thin spaces between the walls of the spiral pathways, as well as the thin walls of the spiral pathway members themselves, in relationship to the long length of the spiral paths results in efficient heat conduction between the concentrated outflowing brine and the neighboring inflowing fluid. The spiral pathways should make at least 5 revolutions.

Fig. 6 shows a detailed view of the manifold section of the desalination system. The exit area, second outflow manifold 53, where the concentrated non- distillated or brine water product of the desalination system is constrained can be seen. The rejected product is constrained on the top by the outlet flat wall 41, a bottom wall and by upright side walls. The rejected product is delivered to the outflow manifold 53 from a spiral pathway that terminates in communication with the shelf 65. The rejected product flows from the center of the system to the exit area in a spiral manner

constrained by the opposed spiral walls and lateral walls of the housing.

Although the walls defining the spiral paths are thin for efficient heat transfer from one side of the wall to the other, the manifolds do not need to be thin since heat transfer requirements are not as important. However, the manifold walls of the desalination system are thinned near the spiral pathways to channel the fluids by in a thin wall environment for heat transfer between fluids. Inflowing sea water, or other fluid to be purified, is channeled between the second spiral wall 30 and the third spiral wall 31. The outlet desalinated product, distilled water, is channeled between the outer spiral wall 37 and the third spiral wall 31. The

rejected non-distilled product or brine of desalination is constrained by the second spiral wall 30 and the outer spiral wall 58. As mentioned earlier the spiral walls are thin for efficient heat transfer between them.. The spacing between the walls is also narrow in relationship to the length of the spiral walls. Efficiency of the desalination system is in part a function of the

efficiency of the heat transfer from the inlet fluids to the outlet fluids. The thin fluid flow channels with thin walls in relationship to the length of the channels and side wall spacing create an extremely efficient inlet to outlet heat transfer subsystem.

Referring to Fig. 7, if the evaporation zone is a shelf, the upslope side of the shelf 65 is a channel formed by the second spiral wall 30 and the third spiral wall 31. The product to be desalinated or distilled exits the channel below the third spiral wall 31 at the product reservoir 45. The evaporation zone or shelf 65 constrains the product to be desalinated or distilled. The temperature of the products to be desalinated or distilled is elevated by the heating elements 67. The temperature of the products is maintained at the boiling point of the products, particularly below the shroud facing the compressor blades.. The vapor from the fluid is drawn through the shroud into the blower where the pressure is increased as the vapor passes through the rotating vanes of the blower. It should be noted that other mechanisms could be used to increase the pressure of the vapor. Note that prior to entering the shroud the vapor pressure at this point could be above or below atmospheric. By maintaining a higher pressure, the boiling point would be higher. Lower overall pressure would lower the boiling point.. Having a lower boiling point typically results in less corrosion of the system components.

Referring to Figs. 8 and 9 the downslope side of the evaporation zone exemplified by shelf 65 is a channel formed by the outer spiral wall 37 and the third spiral wall 31. Fluid to be vaporized is in the

downslope reservoir 45 open to the intake shroud of the blower. Fluid not vaporized flows into the spiral path formed by spiral wall 37 and third spiral wall 31. On the other hand, pressurized vapor from the compressor flows to the region below the evaporation zone as described above. Pressure at the lower plenum region is great enough that the temperature of the condensation of the distillate is greater than the temperature of the evaporation zone. Because the temperature of the condensate is greater than the temperature of the initial boiling product or vaporization temperature, heat flows from the condensate to the other fluids, including the evaporation zone itself. The heat flow is through the zone from the bottom to the top. Condensed distillate falls from the underside of the zone to the condensate reservoir where it enters the central spiral pathway.

Claims

Claims

1. A desalination or distillation system comprising:

a housing having spaced apart side walls and an interior structure with a radially outer plenum portion with tripartite spiral fluidic pathways and a radially inward plenum portion with a heated evaporization zone with an upward compressor;

the tripartite spiral fluidic pathways having a lateral extent spanning the distance between spaced apart side walls, with a first pathway for outflowing

distillate, a second spiral pathway for inflowing . sea water and a third spiral pathway for outflowing non- distilled product or brine;

the evaporation zone receiving inflowing sea water from an inward end of the second spiral pathway, the zone yielding heated vapor directed into a shroud directing the vapor to a radially inward portion of the compressor;

the zone expelling non-distilled product or brine into the third spiral pathway;

the plenum receiving pressurized vapor as steam from a radially outward portion of the compressor and expelling steam into the first spiral pathway for heat exchange with inflowing sea water in. the second spiral pathway, thereby cooling the steam to produce distilled water;

whereby distilled water is delivered as product.

2. The apparatus of claim 1 wherein the radial blade compressor is driven external to the opposed side walls of the housing.

3. The apparatus of claim 1 wherein the opposed side walls of the housing are round.

4. The apparatus of claim 1 wherein the tripartite spiral fluidic pathways are self supporting.

5. The apparatus of claim 1 wherein the evaporation zone is a shelf having heating elements.

6. The apparatus of claim 1 further comprising, three manifolds terminating the tripartite spiral fluidic pathways of the radially outer portion of the housing, including a first distilled water, product manifold, a second inflowing sea water manifold and a third non- distilled product water manifold.

7. The apparatus of claim 5 wherein the shroud is supported on the shelf.

8.. The apparatus of claim 5 wherein the shelf has at least one tunnel there through allowing steam to pass from an upper portion of the plenum to a lower portion of the plenum.

9. The apparatus of claim β wherein each of the manifolds has a fitting as a fluid passageway for external fluid communication with the manifolds.

10. The apparatus of claim 1 wherein the spiral pathways make at least 5 revolutions.

11. The apparatus of claim 8 wherein distilled condensate formed in the lower portion of the plenum is fed to the first spiral pathway.