IMPROVED JET NOZZLE FOR MULTIJET MULTISPRAY

CONDENSER

FIELD OF INVENTION:

This invention relates to an improved Multijet Multispray Condenser e.g. that used in machinery for manufacture of sugar. More particularly it relates to improvements in jet nozzle for use in the Multijet Multispray Condenser.

BACKGROUND AND PRIOR ART OF THE INVENTION:

In sugar factories, the boiling of the sugar syrup takes place under vacuum. The vapours produced by the boiling of the syrup in the Pan are condensed by cold water in a Condenser, so as to recover the water, which can be further cooled and recycled. Also, condensation of the vapors prevents environmental pollution.

Condensers as the name indicates, help to 'condense' or convert vapors to liquid. Condensers are of two types- direct contact and indirect contact.

In direct contact condensers, the vapours and cooling water are in direct contact with each other. This allows more efficient heat transfer. Another advantage of direct contact condensers is that they are relatively cheap to manufacture.

Indirect contact condensers (also called surface condensers) on the other hand do not allow the vapours and cooling water to come into direct contact with each other. They have a shell-tube design, in which vapours can be condensed either in shell section or in tubes. Indirect contact condensers offer the advantage that the water obtained is of 'high purity' called 'distilled water' which has beneficial uses in industry. Hence, they are used mainly in applications where separation of vapour/condensate from the cooling water is required. However, surface condensers are more expensive as compared to direct contact condensers(Sugar

Technology - by Verlag Dr. Albert Bartens KG - 1998 edition - Chapter 12.6 - Condensation, pages 806-808).

The multijet multispray condensers are a category of direct contact condensers, because the vapours and cooling water are in direct contact with each other. In these type of condensers, a combination of jets and spray nozzles is used to not only condense the vapours, but also create vacuum, so that the vapours and also air/non-condensable gases get sucked into the condenser and thereafter condensed/ejected.

Conventionally, Spray nozzles are primarily used for condensation of vapours while the jet nozzles are mainly used for creation of vacuum by compression and ejection of air/non-condensable gases. This is effected by water jets emerging from the jet nozzles (jet pump principle). Therefore requirement of a vacuum pump for direct contact and surface condensers is eliminated.

It is known that the air or non-condensables and vapour load content entering the condenser varies, making it necessary to extract/condense varying quantities of air/vapour from the condenser. Multijet Multispray Condensers have been used for the purpose, but unless means are employed for varying their capacity in accordance with variations in the amount of air/vapour to be handled, they are wasteful of cooling water and thus energy.

Several efforts at improving the efficiency of jet condensers have been made. (Patents Nos. IN176969, IN181837, US5971063). In general, efforts have mainly focussed on improving the efficiency, by increasing the surface area of cooling water exposed to vapours (Patent Nos. US1015822, USl 151259, US1516939, US3761065, IN153360); by increasing the entraining capacity of the apparatus (Patent Nos. US2382391, GB315492, GB344328, US4810170); by positioning, number and controls of the nozzles (spray as well as jet) (Patent No. IN181837, Indian Patent Application No. 1124/DEL/2002, Patent Nos. US 1945973,

US4274812, US5628623, US5791063, US6619568, US6746001, PCT Application No. WO2005/003616, US Patent Application No. US2002/079384) and by correlation of sizes (Patent Nos. IN165498, US6164567, US6220578, US6224042, US6250890, US6261067, US6276903, US6312230, US6364626).

Theoretically the efficiency of the condensers can also be increased by varying the capacity of spray and jet nozzles. This can be done by dividing the water box feeding the nozzles into two, three, four or more chambers, with each chamber having its own set of nozzles. The inlet to each chamber in turn is being controlled by a valve, which is regulated by air/vapour load and temperature of the inlet cooling water.

Alternatively the spray and jet nozzles may be governed by a piston and plunger mechanism, individually or by dividing them into two and three stages respectively, each stage joined commonly by a rubber tube that provides high pressure governing liquid i.e. water, as described in our patent application numbered 1124/DEL/2002, now abandoned, or by some other means.

However, economic as well as technical considerations limit such an arrangement. Such an arrangement is attended with the disadvantage of increase in the construction and maintenance cost as well as the technological demand for the control system. Also to work the nozzle piston and plunger mechanism the requirement of optimum pH of governing liquid i.e. water along with pressure generating means add to the equipment and energy requirements thus affecting the overall economics.

Further, as is seen, that ejection of air/non-condensable gases is primarily controlled by the jet nozzles while the condensation of vapour is principally done by spray nozzles. The two are designed according to their specific requirements. The spray nozzles spray the cooling water in a mist form so as to provide maximum surface area for contact with the incoming vapour whereas jet nozzles emit high speed water jets so as to entrain air/non-condensable gases. Besides

other reasons for low efficiency of multijet multispray condensers, one of the reasons is the improper design of the jet nozzles.

It is known that if several jets issue from a ring of nozzles which are angled so that the jets converge, the entraining effect is greater than that of a single jet. Further if jets from a ring of nozzles converge onto the axis of a further jet issuing from the centre of the ring, the resultant combined jet takes longer to diffuse and the suction effect is significantly increased. (Patent No. US4274812).

However, high speed jets emerging from jet nozzles being used in multijet multispray condensers are generally compact and homogeneous streams of fluid, with all parts substantially moving in the same direction and at substantially same speed. Such compact and homogeneous jets or streams are not well adapted to inductively entrain air, water or other fluids.

It is also known that swirling of the inlet water improves the entrapment of air or fluid entering the condenser and also increases the vacuum in the suction line. Swirling of the propellant coolant water in the coaxial passages and the fluid to be aspirated enables contact to be made between the different fluids with a minimum of shock and turbulence. Swirling of the fluid in the diffuser chamber creates a smooth flow condition and tends to eliminate short-circuiting back to the low pressure area near the entrance to the diffuser area. In addition swirling creates centrifugal force which increases the vacuum in the passage carrying the fluid to be aspirated thereby to increase the pressure head across the jet pump and to increase its efficiency. (Patent Nos. US3134338, US4810170)

Opening out of such a compact jet, by providing a swirl motion to the inlet propellant water increases the effectiveness of the said jet. In other words, increase in expansion of compact jet stream increases the carrying capacity of the propellant jet stream. However, such expansion cannot be carried too far since it will result in undesirable losses in kinetic energy. Various means have been used

in the prior art to impart such a swirl (rotary) motion, either by providing a plurality of spaced vanes or guides or deflectors or other modifications mounted within the jet nozzle. (Patent Nos. US1031143, US2486019, US3134338, US3694107, US6210123, DE3718971, US Patent Application No. US2005/0133628)

However, such attempts have resulted in big hydraulic energy losses. This is mainly due to turbulence created by friction and flow stream irregularities. Disadvantages of the same are lowering of efficiency of the nozzles, thus affecting overall condenser efficiency.

The present invention has been able to overcome the disadvantages associated with the prior art jet nozzles in a simple but novel manner. The innovation involved in the present invention lies in imparting a whirl to the water jet, with minimal energy losses, due to unique positioning and angle of the guide vanes at the entry level of water, which has not been reported anywhere in the prior art for jet nozzles.

OBJECT OF THE INVENTION:

An object of the present invention is to provide a simple but novel jet nozzle for multispray multijet condensers in which energy losses have been minimized.

SUMMARY OF INVENTION:

The present invention discloses a simple but novel jet nozzle in which the disadvantages associated with existing nozzles have been overcome. The innovation in the present invention lies in imparting a whirl to the water jet, with minimal energy losses. This has been achieved due to two factors-unique positioning of the guide vanes at the entry level of water (instead of the high velocity zone inside the nozzle) and at a particular angle to the nozzle axis. As a result of full and unobstructed flow of pressurized water without turbulence,

energy losses are minimized, enabling it to maintain its thrust (impact) even though a 'spray effect' has been imparted to the emerging jet stream. Another advantage of the innovation is, that it results in simplified technical controls of the spray nozzles due to decreased water requirement of the spray nozzles.

STATEMENT OF INVENTION:

Accordingly, the present invention relates to a jet nozzle comprising: upper inlet chamber; means to allow tangential entry of water and means for imparting swirl to water; plurality of vanes placed at a particular angles at the inlet of the nozzle; and outlet; wherein said jet nozzle allows tangential entry and imparts swirl to water without loss of jet action owing to particular positioning of the guide vanes and at a particular angle at the inlet point of water into the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS:

Fig.l - Sectional elevation of conventional multijet multispray condenser. Fig.2 - Jet Nozzle as per present invention. Fig.3 - Longitudinal section of the Jet Nozzle along line A-A in Fig.2.

Fig.4 - Cross-section of the inlet chamber of the Jet Nozzle along line B-B in Fig.2.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE DRAWINGS:

It has been observed in the prior art that efficiency of jet nozzle employing jet pump principle is an important factor hi the overall efficiency of the Multijet Multispray Condenser Fig.l and that each percentage point of improvement of jet pump efficiency can be of substantial economic value.

Accordingly present invention provides a jet nozzle comprising: upper inlet chamber; means to allow tangential entry of water and means for imparting swirl to water; plurality of vanes placed at a particular angles at the inlet of the nozzle; and outlet; wherein said jet nozzle allow tangential entry and impart swirl to water without loss of jet action owing to particular positioning of the guide vanes and at a particular angle at the inlet point of water into the nozzle.

In an embodiment of the present invention the upper inlet chamber of the jet nozzle is axisymmetric cylindrical inlet chamber.

In another embodiment of the present invention the means for entry of water having vanes at the periphery of the upper cylindrical inlet chamber.

In still another embodiment of the present invention the vanes are positioned at an angle of 3-4 degrees to the longitudinal axis of the nozzle.

In yet another embodiment of the present invention the outlet is having a lower outlet chamber whose flow through channel has an inlet section converging in the flow direction.

In a further embodiment of the present invention the outlet is provided with a cylindrical outlet section with a sharp outlet edge.

In one more embodiment of the present invention said nozzle operates at a reduced water pressure of 1.1768- 1.275 bar Absolute.

Fig.l refers to the conventional multijet multispray condenser 1 comprising a cylindrical shell 2, a plularity of spray nozzles 3, a plularity of jet nozzles 4, a cold water inlet 5, an inlet 6 for vapours, the shell 2 having a tapering cone 7 and a Reducer 8 continuing into a cylindrical tail pipe 9 and a Diffuser 10 opening into the hot water well/channel 11.

Fig. 2 relates to a jet nozzle of the present invention.

After considerable research and experiment we have been able to invent a novel jet nozzle which not only removes the non-condensables but also performs an additional function of condensation, thereby reducing the load on spray nozzles employed specifically for the purpose of condensation, without losing the necessary thrust (impact) required for entrainment by reducing the energy losses. As a result of the innovation, the condenser system has been made simple, economical and efficient.

The said nozzle Fig.2 & 3 consists of axisymmetric upper cylindrical inlet chamber 12 with a cap 13 at top and all around tangential water entry 14 through guide vanes 15 and the lower outlet chamber called the mouth 16 whose flow

through channel has an. inlet section 17 converging in the flow direction and a cylindrical outlet section 18 with a sharp outlet edge 19.

According to the salient feature of the invention, guide vanes 14 parallel to the longitudinal axis of the nozzle are located all around the periphery of the upper cylindrical inlet chamber 12 i.e. at the inlet of the propellant cooling water in the nozzle, making an angle between 3 degrees to 4 degrees with the axis Fig.4.

The tangential water entry 14 at an angle of 3 degree to 4 degree is particularly favourable as compared to axial entry since the water is given a mechanical rotation at a stage of low velocity. Redirection is achieved without any significant energy loss as a result of which turbulence is substantially avoided. Moreover, experiments have indicated that the vane angle of 3 degree to 4 degree provides low centrifugal force so that the emerging jet stream diverges to a small degree. Best results were obtained in a nozzle with a vane angle of 3.5 degrees. The cap

13 has a depression in the middle protruding into the upper cylindrical inlet chamber 12 which assists in vortex formation.

The experiments were performed on nozzles having orifice size ranging from 18 mm to 26 mm with cold water pressure of 1.1768 - 1.275 bar Absolute and pressure of 0.133 bar Absolute inside the multijet multispray condenser. The emerging jet stream diverges 5 deg.(for 18 mm nozzle) to 7.5 deg.(for 26 mm nozzle) more than the jet stream emerging from conventional jet nozzles used in multijet multispray condensers e.g. in sugar industries.

The water flows through the nozzle unobstructed since there are no vanes or wings or other modifications to impart swirling motion in the mouth where the velocity of the water increases considerably. Further, the nozzle is constructed from engineering thermoplastics which exhibits reduced friction losses as compared to conventional nozzles made of cast iron or stainless steel. The inherent potential energy thus converts into kinetic energy without any significant

energy losses. This enables the emerging jet stream to maintain its impact despite increasing the area covered by it.

Such an increase in surface area has been found to assist in condensation of vapours too without in any way compromising with its primary function of entrainment of air/non-condensable gases. Imparting a rotary motion to the water jet further assists in the entrainment of air or non-condensable gases.

Further, due to lowered energy losses the nozzle operates at a reduced pressure range as compared to conventional nozzles. The said nozzle operates optimally at a water pressure of 1.1768 - 1.275 bar Absolute as compared to a pressure of

1.471 - 1.961 bar Absolute for conventional jet nozzles used in multijet multispray condensers e.g. those applicable in sugar industry. The guide vanes located at a position as described also perform the function of a strainer thereby preventing fouling of the mouth of the nozzle.

It will be appreciated that tangential entry of water at an angle lesser than 3.0 degrees results in increased turbulence, whereas entry at an angle greater than 4.0 degree increases the centrifugal force. As a result, the emerging jet stream diverges at a wider angle resulting in significant kinetic energy losses, thus affecting the impact (thrust) of the emerging jet stream.

Such a design therefore reduces the water requirement for the spray nozzles and also the technological demand on the control systems of spray water nozzles. On the other hand, water supply to jet nozzles can be increased to effect both condensation and ejection/entrainment. Furthermore, it has been found in test results that the condenser functions efficiently with a water distribution ratio of 1 :2.3 for spray to jet nozzles. This can be achieved by appropriately selecting the size of the spray and jet nozzles. The water distribution ratio, however, should not be less than 1 : 1.5 for spray to jet nozzles. This eliminates the need for removing

separately the spray water and the condensate through a separate spray water tail pipe as described in Patent No. INl 76969.

The use of the jet nozzle of the invention performing the additional function of condensation besides its primary function of air ejection/entrainment has enabled to operate spray nozzles only when the vapour load becomes more than which can be handled by the said novel jet nozzles. This further saves water as well as energy required to pump the same, thereby increasing the overall efficiency of the system.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit and scope of the present invention as described.

List of Reference Symbols:

1. Conventional Multijet Multispray Condenser

2. Cylindrical Shell

3. Spray Nozzles

4. Jet Nozzles

5. Cold Water Inlet

6. Vapour/Air Inlet

7. Cone

8. Reducer

9. Tail Pipe

10. Diffuser

11. Hot well or channel

12. Upper cylindrical inlet chamber

13. Cap

14. Tangential Water Entry

15. Guide Vanes

16. Lower Outlet Chamber (Mouth)

17. Inlet Section of Mouth

18. Outlet Section of Mouth

19. Sharp Outlet Edge of Nozzle.