GB2051341A - Fluid circulating systems - Google Patents

Abstract

A fluid circulating system for instance a hydronic heating system, utilizes a Venturi-type device (20) to effect communication between the circulating system and a storage tank (26). The storage tank, which is maintained at ambient atmosphere pressure, is connected to the throat (20b) of the Venturi. The inlet and outlet of the Venturi are connected to the outlet and inlet, respectively, of a pump (10). The pressure differential between the Venturi throat and the Venturi inlet remains constant. Thus, if the Venturi throat pressure is set so as to be atmospheric during normal operating conditions of the system, when the system pressure drops, the Venturi throat pressure will drop below atmospheric and draw water from the storage tank into the circulating system. Conversely, if the pressure in the system should rise, the Venturi throat pressure would rise above its ambient atmospheric level to thereby vent some of the water from the system back into the tank. <IMAGE>

Description

SPECIFICATION Venturi pressurizer for fluid circulating system FIELD OF THE INVENTION This invention relates to pressure control systems for fluid circulating systems.

BRIEF DESCRIPTION OF THE INVENTION In all fluid circulating systems, some means must be provided to accommodate the expansion and contraction of the fluid within the system.

Typically, this means has been a pressurized accumulator tank connected to the system such that when the fluid expands, a portion of it passes into the accumulator tank to prevent undue pressure buildup within the system. The accumulator tank also provides a small supply of fluid to the system when the fluid in the system cools to prevent air from entering the system and to provide a more consistent heat transfer. In the past, such systems have required the accumulator tank to be pressurized, since the fluid within the system itself is also pressurized. The requirement of a pressurized vessel has increased the cost and complexity of such fluid circulating systems and has increased the maintenance requirements due to the need for inspecting the pressurized vessel and its associated components.

The use of a Venturi structure in a water circulating system is known in the art, and is specifically shown in U.S. Patent 2, 265,108. This patent, however, utilizes the Venturi structure interconnected between a storage tank, a heater and an incoming water supply such that the action of the incoming water supply passing through the Venturi creates a low pressure area at the Venturi throat which serves to stimulate the circulation of the water from the storage tank.

Thus, the Venturi structure is utilized as a jetpump device to assist the circulation of the water within the fluid system.

The use of an ejector, or jet-pump structure to circulate water through a system, or assist in such circulation is well-known and is shown by the following U.S. Patents: 566,904,1,418,583, 2,404,114,2,843,142, 3,274,065 and 3,730,646. However, in none of these patents is there a disclosure that a Venturi structure can be interposed between an open storage tank and a fluid circulating system such that the fluid circulating means passes a portion of the fluid through theVenturi to control the addition or venting of fluid between the pressurized system and the atmospheric storage tank.

It is also known to utilize a water storage tank open to atmospheric pressure in a fluid circulating system, as shown in U.S. Patent 3,554,441. The storage vessel is connected to the fluid circulating system so as to allow water to flow into and out of the system depending upon the relative difference between the system pressure and the pressure in the vessel. Overflow of this vessel is prevented by interconnecting it with a secondary storage vessel located at a lower level.

SUMMARY OF THE INVENTION The present invention relates to means for controlling the addition and venting of a fluid between a storage tank, opened to atmosphere, and a closed loop fluid circulating system. The means to accomplish this comprises a Venturi connected to the system such that its inlet communicates with the outlet of a pump while the outlet of the Venturi communicates with the pump inlet. The throat of the Venturi is connected to the storage tank and is normally at the same pressure as the storage tank (plus any hydrostatic head due to elevation) such that no flow takes place between the tank and the system. A small amount of fluid from the pump outlet circulates through the Venturi and back into the pump inlet.The amount circulating through the Venturi is relatively small and does not interfere with the adequate functioning of the remainder of the fluid circulating system.

The pressure differential between the fluid at the Venturi inlet and the Venturi throat is fixed due to the design of the Venturi. Thus, if the pressure in the system, and consequently at the Venturi inlet, increases, the pressure at the Venturi throat will also increase to maintain a constant pressure differential. Once the Venturi throat pressure rises above atmospheric, a portion of the fluid will pass from the system through the Venturi throat and into the storage tank, which is open to atmospheric pressure. Conversely, if the fluid pressure within the system should fall, the pressure at the Venturi throat also drops to below ambient atmospheric, thereby forcing fluid to flow from the storage tank, into the Venturi throat and subsequently into the fluid system.

Thus, it can be seen that the Venturi control device, according to the invention, provides a simple and reliable means to automatically control fluid flow between a storage tank and a fluid circulating system based upon the pressure within the system.

Thus it will be appreciated that the invention provides, at least in its preferred embodiments, a pressurized fluid circulating system which does away with the pressurized accumulator system while tank structure, means for automatically adding or venting fluid from the fluid flow system, a Venturi structure to control the addition or venting of the fluid from the fluid flow system, and means to add or vent fluid from the fluid flow system and which eliminate the necessity for a separate fill control valve and the resultant complexities inherent in such valve structure.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of a fluid circulating system including the Venturi pressurizer system according to the invention.

Figure 2 is a graph of the pressure at various points along the longitudinal axis of the Venturi shown along in Figure axis 1.

Figure 3 is a longitudinal cross-section of the Venturi shown in Figure cross-section 1.

Venturi shown in Figure 1.

Figure 4 is a partial sectional view of a pump housing incorporating the Venturi structure shown in Figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The fluid flow control system according to the invention is schematically shown in Figure 1 and comprises a pump or other circulating means 10 having its inlet connected to a return line 12 and its outlet communicating with an outlet line 14.

For the purposes of explaining the invention, it will be assumed that the fluid flow system is a hydronic heating system which utilizes water as the circulating medium. It will be understood, however, that this assumption is for explanatory purposes only; and that the Venturi flow control device according to the invention can be utilized with any closed loop fluid circulating system.

The outlet line 14 transmits the water from the pump 10 to a boiler 16 in which the water is heated and thereafter passed to the remainder of the system (not shown) via a line 18. The remainder of the fluid system (not shown) may be a series of heat radiating devices to transfer heat from the fluid to an enclosed space. After giving up its heat, the water returns to the pump via the return line 12.

A Venturi 20, having an inlet 20a, a throat 20b, and an exit 20c is connected to the circulating system via conduits 22 and 24 such that a small portion of the water exiting the pump outlet passes into the inlet 20a, while the fluid exiting from the exit 20c returns to the pump 10 via a line 24. The throat 20b is connected to a water storage tank 26 via-a conduit 28. Since the storage tank 26 is open to atmospheric pressure, the pressure at the Venturi throat is also at atmospheric pressure such that, under normal operating conditions, no fluid transfer takes place between the tank and the circulating system. The design of the Venturi is such that there is a constant pressure differential between the fluid pressure at the inlet 20a and the fluid pressure at the throat 20b.

The pressures at the inlet, throat, and exit, designated P1, P2 and P3 respectively, are diagrammatically shown in Figure 2. The difference between pressure P1 and P3 is due to the frictional losses as the fluid passes through the Venturi. The pressure differential between pressure P1 and pressure P2 remains constant, thus as the pressure in the circulating system (P 1) either increases or decreases, the Venturi throat pressure (P2) will correspondingiy increase or decrease. Thus, as the pressure within the fluid flow system increases, due to increasing temperature or various other factors, the pressure at the Venturi throat 20b will correspondingly increase. This increase in pressure P2 creates a pressure differential between the Venturi throat 20b and the storage tank 26, which remains at atmospheric pressure.This pressure differential causes water to pass from the system into the storage tank 26 via the line 28. This provides the requisite venting of the fluid flow system to prevent a pressure buildup which may cause malfunctions and, in the extreme case, rupture of the fluid flow system.

A similar action takes place when the pressure within the fluid flow system (P 1) decreases, since the corresponding decrease in Venturi throat pressure (P2) causes the Venturi throat pressure to decrease below its normal atmospheric pressure thereby creating a pressure bias in favour of the storage tank 26. Water from the tank passes into the system via the line 28, Venturi 20 and line 24. This provides the automatic addition of water to the system to prevent damage or malfunction.

The Venturi is shown in detail in Figure 3 and comprises a housing 30 having a filter screen 32 attached to its inlet end. Contained within the housing 30 are a nozzle 34 and a diffuser 36, the area between the nozzle 34 and diffuser 36 forming the throat portion 20b of the Venturi. The throat portion 20b communicates with the line 28 via a plurality of openings 38 in the housing 30.

The housing 30 also has two outlet ports 40 which communicate with the fluid system via the line 24 to allow the fluid to flow back into the pump inlet. A valve mechanism, indicated generally at 42 is provided adjacent the exit end of the Venturi to control the amount of fluid that flows through the Venturi. The valve mechanism also has two ports 43 which, when aligned with the two outlet ports 40 in the housing 30, allow the maximum flow through the system. A change in. the alignment of the two sets of ports by means of a screwdriver slot 44 in the valve mechanism 42 allows adjustment of the flow through the Venturi and, consequently, the adjustment of the pressure in the system.

The screen 32, nozzle 34, diffuser 36, and valve 42 are held in place by a bowed snap ring 45.

Sealing means in the form of rubber "O" rings 46 are provided on the valve 42. The Venturi shown in Figure 3 may be attached externally to the system via separate conduits 22 and 24 as indicated in the schematic diagram of Figure 1, or it may be integrated into the pump housing as shown in Figure 4. In this case a pump housing 47 is fabricated having a passageway 48 therein which, at one end, communicates with a pump outlet passage 49 and, at or near its opposite end, communicates with a pump inlet 50. The housing 30, containing the elements previously described in reference to Figure 3, is located in this passageway in the orientation shown in Figure 4.

This installation provides a compact pump/control device structure without the necessity of external piping and plumbing. Although a particular orientation of the Venturi is shown in Figure 4, it is understood that any orientation that is practicable and which allows the Venturi inlet to communicate with the pump outlet and the Venturi outlet to communicate with the pump inlet is considered within the scope of this invention.

Claims (10)

1. Apparatus comprising a closed loop fluid circulating system having means for circulating fluid through the system, said means having an inlet and an outlet, and a fluid storage tank to store the fluid at atmospheric pressure, Venturi tube means connected to the fluid circulating system and to said storage tank to control the flow of the fluid between the storage tank and the system such that when the fluid pressure within the system falls below a predetermined value, fluid flows into the system from the storage tank through the Venturi tube, and when the fluid pressure in the system rises above a predetermined value, fluid flows from the system into the storage tank through the Venturi tube.

2. Apparatus according to Claim 1, wherein means are provided for passing a portion of the fluid from the outlet of the circulating means through the Venturi tube and returning that portion to the system upstream of the pump inlet.

3. Apparatus according to Claim 2, wherein the Venturi tube is located within a housing of the circulating means.

4. Apparatus according to Claim 3, wherein said Venturi tube is located within a passage formed integrally with said housing.

5. Apparatus according to Claim 2 or 3, further comprising valve means to control the amount of fluid passing through the Venturi tube.

6. Apparatus according to Claim 5, wherein said valve means is located within a housing of the Venturi tube.

7. Apparatus according to any of Claims 2, 3, 4, 5 and 6, wherein said storage tank is connected to the Venturi tube at the Venturi throat.

8. Apparatus according to Claim 1, substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.

9. Apparatus according to Claim 8, wherein the Venturi is substantially as described herein with reference to and as illustrated in Figure 3 of the accompanying drawings.

10. Apparatus according to Claim 8, wherein the Venturi and the circulating means are substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.