NZ239015A - Mixing hot and cold fluids having differing pressures, method and apparatus - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £39015 ^39015 Patents Form 5 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 239015 17 July 1991 AN IMPROVED FASTFLOW SYSTEM N.Z. PATENT OFFICE ■241UI 1992 _ RfCEW-O WE, G METHVEN & CO LIMITED of 447 Rosebank Road, Avondale, Auckland, New Zealand being a New Zealand Company, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: 3 9 01 5 This invention relates to a mixing unit and particularly to a mixing unit suitable for mixing hot and cold liquids prior to discharge of the mixed liquids.

At present a number of systems are available for mixing hot and cold liquids, particularly water, and an example is the mixing unit designed by the applicant and described in their New Zealand Patent Application No. 227746. Although the unit described in specification No. 227746 is a clear improvement over mixing units used in the past it suffers from poor performance under special conditions such as tempering valve supply and lower mains cold pressure supply.

Presently the Government is emphasising the danger of having hot water temperatures higher than 55 8C, therefore the percentage of customers who will be using tempering valves will increase. That is there is no adjuster to regulate the • flow of water being emitted from the primary nozzle referred to in Patent specification No. 227746.

An object of the invention is to overcome the above identified disadvantage and provide eux improved mixing unit.

An object of this invention is to enhance performance under such conditions as tempering valve supply and lower mains cold pressure.

Further objects and advantages of the invention will be apparent from the following description which is given by way of example only.

According to a first aspect of the invention there is provided a method of mixing first and second fluids, which 238015 are at different pressures, the method including providing for the fluid at a first pressure a first flow path and for the fluid at a second pressure a second flow path, said flows of fluid through the first and second flow paths converging to a mixing unit in which the fluids are mixed, the second flow path being restricted in cross sectional area by an insert through which the higher pressure flow of fluid passes to a mixing zone, in the mixing unit the second flow path having attached thereto or fitted therein a flow control adjustable from the exterior of the mixing unit to enable a differing venting area to be created, which in turn creates a differing flow rate.

The mixing zone can include a secondary nozzle through which the mixed flow of fluid passes to an outlet.

According to a second aspect of the invention there is provided a mixing unit for carrying out the above method of mixing fluids.

According to a third aspect of the present invention there is provided a mixing unit for mixing first and second fluids, which are at different pressures, said mixing unit including a housing to which is attached control means which control the flow of said first and second fluids through first and second flow paths respectively, the housing having formed therein or inserted therein a nozzle which reduces the cross sectional area of the second flow path, the nozzle having an adjustable flow control inserted on the inlet side of the nozzle part through which the second flow passes to thereby create in a mixing zone a jet or thrust of the secpn^Trr--^ , J /\ p o\ " " ./V . U \ "6 Kc 1995 * ;o ;239015 ;fluid which draws from the first flow path a greater volume of fluid to improve throughput of the first fluid and the mixing characteristics of the fluids, the flow control being adjustable from the exterior of the housing. ;Movement of the adjustable flow control creates a differing venting area which in turn creates a differing flow rate. ;The mixing unit can be used for mixing fluids at different pressures wherein the first flow is at a lower pressure than the second flow. ;Further aspects of the invention which should be considered in all its novel aspects will become apparent from the following description which is given by way of example only. ;Examples of the invention will now be described with reference to the drawings accompanying the provisional specification in which: ;Figure 1 is a diagrammatic section through a mixing body of a unit according to the invention which is designed to be used as a shower mixer. ;In the following example the invention is described with reference to the control of high pressure cold water to be mixed with hot water at a lower pressure. ;The pressures respectively of the hot and cold water are standard domestic or industrial pressures as currently available and used in New Zealand and the United Kingdom which are to a limited degree also used in Australia. ;Typically the pressures of domestic cold water ;N.Z. —r _ 4 _ ;239015 ;supplies are at 70 - 100 psi and the thermostats of hot water systems are set to supply water at a temperature of about 55"C to 65°C. ;Typical New Zealand domestic hot water supply pressures from header tanks and pressure reduction valves are about 2 -10 psi. ;It is to be appreciated that with minor modifications the invention can be adapted to operate with other fluids and other than standard fluid pressures, for example, equal pressure situations. ;The example shown in Figure 1 is a mixing unit adapted to mix hot and cold water for a shower. ;The unit is generally indicated by arrow 1 and has a housing 2 to which are fixed or attachable connecting tubes 3 and 4 for hot and cold water supplies respectively. In normal domestic situations the tubes 3 and 4 are constructed from 15mm copper or plastics tube. The housing 2 is closed at one end 5 by a nozzle adjuster 5. ;An opposite and 7 of the housing 2 has mounted therein a nozzle holder 8. In this construction there is provision for a secondary nozzle 9. In trials the applicants have established that with a bore 10 of 2.3mra in a primary nozzle 15 the bore of the secondary nozzle 9 should be 6ram. The nozzle adjuster 6 may have a 30° taper of complementary dimensions to a shoulder 16 of the nozzle 15. ;In use the flow of water is controlled by hot 11 and cold 12 taps. The cold tap control is used in conjunction ;239015 ;with the preset cold water nozzle adjuster 6. At installation the position of the adjuster is set by an installer to provide a desired comfort zone temperature. The adjuster regulates the volume of cold water allowed to mix with the hot water supply. The flow rate of the mixed water will be dependent on the conditions and pressures of the hot and cold water flows. ;The mixing of the water is enhanced in the mixing zone 13 by the high pressure water jet drawing water from the hot connecting tube 14. ;In an equal pressure situation the nozzle is removed and the secondary nozzle 9 relocated into the hole vacated by the nozzle. ;Tests were done under the combination of the following supply pressure conditions and nozzle configurations; ;Cold Pressure (kPa) = 280,520 ;Hot Pressure (kPa) = 15 (static) ;Hot and cold flow rates were measured and then mixed flow rates and hot/cold flow ratios were calculated. On adjustable nozzle configuration both handles were fully opened, while on fixed nozzle configuration the hot handle was fully opened. Cold handle opening was varied. ;10 (running, Hot only) Nozzle Configuration A 2.15 Fixed Primary ;B 2. 3mm Primary with Adjuster C 2.5mm Primary with Adjuster ;6 ;23901 ;The test results are listed in the attached Tables 1, 2 and 3. Moreover, mixed flow rates at 40°C corresponding to different practical temperature installation situations are listed in the attached Tables 4 and 5. ;From values in Tables 2 and 3, as expected the adjustment can provide an adjustable flow feature. Also, it was proved that the adjustable nozzle can provide a suction effect as hot flow at mixing is higher than the individual flow value at most of the adjustable range. In order to evaluate the new design, the performance curves of the 2.15mm fixed primary nozzle configuration are used as a basis for comparison. ;At higher main pressure supply (520 kPa) both the 2.3mm and the 2.5mm adjustable nozzles performed similarly except that the latter one has a higher peak than the former. When compared with the 2.15mm fixed nozzle, both adjustable nozzles performed better. With the same inlet temperature combinations of hot/cold flow ratio, adjustable nozzles can give a higher mixed flow rate (see attached Tables 4 and 5). ;At medium main pressure supply (280 kPa), the 2.3mm adjustable nozzle performed similarly to the 2.15mm fixed one, except that the former had a higher peak. Compared with the 2.5mm adjustable nozzle, the 2.3mm one performed slightly better as it can deliver slightly more mixed flow at the same hot/cold flow ratio, despite it having a lower peak. ;Combining all the above comparisons, the 2.3mm adjustable nozzle configuration gave the best overall performance. ;PATENT OFRCr I ;7 ;New Design Specification of Mixer for unequal pressure systems. ;incorporated in bottom plug ;Range of cold flow adjustment at 520 kPa : 2.0-7.0 1/min at 290 kPa : 1.5-5.0 1/min Operating Water Temperature ;Hot - Minimum 55 °C ;Primary Nozzle Secondary Nozzle Cold Flow Adjuster ;2.30mm Dia ;6.00mm Dia ;30° incl taper plunger ;Maximum 75 °C ;Cold ;Minimum 5 °C ;Operating Water Pressure Hot ;Minimum 15 kPa stagnation 10 kPa at running Minimum 280kPa stagnation ;Cold ;TABLE Is 2.15nnn Fixed Primary Nozzle ;Pressure (kPa) ;Flow (1/min) ;Hot/Cold ;Hot/Cold ;Hot ;Cold ;Mixed ;Flow Ratio ;15/520 ;7.61 ;5.82 ;13.43 ;1.31 ;6.76 ;4.87 ;11.63 ;1.39 ;6.06 ;4.17 ;10.23 ;1.45 ;5.49 ;3.65 ;9.14 ;1.50 ;5.08 ;3.05 ;8.13 ;1.67 ;4.88 ;2.70 ;7.58 ;1.81 ;4.40 ;2.04 ;6.44 ;2.16 ;15/280 ;5.89 ;4.05 ;9.94 ;1.45 ;5.34 ;3.34 ;8.70 ;1.60 ;4.76 ;2.55 ;7.31 ;1.87 ;4.46 ;2.03 ;6.49 ;2.20 ;4.32 ;1.38 ;5.70 ;3.13 ;TABLE 2 ;• 2.3mm Primary Nozzle with Adjuster ;Pressure (kPa) ;Flow (1/min) ;Hot/Cold ;Hot/Cold ;Hot ;Cold ;Mixed ;Flow Ratio ;15/520 ;8.06 ;7.06 ;15.12 ;1.14 ;7.46 ;6.11 ;13.57 ;1.22 ;7.13 ;5.02 ;12.15 ;1.42 ;6.76 ;4.24 ;11.00 ;1.59 ;6.48 ;3.55 ;10.03 ;1.83 ;5.97 ;3.00 ;8.97 ;1.99 ;5.60 ;2.51 ;8.11 ;2.23 ;4.81 ;1.91 ;6.72 ;2.52 ;15/280 ;6.15 ;4.94 ;11.09 ;1.24 ;5.61 ;4.06 ;9.67 ;1.38 ;5.16 ;3.15 ;8.31 ;1.64 ;4.99 ;2.68 ;7.67 ;1.86 ;4.45 ;2.16 ;6.61 ;2.06 ;4.18 ;1.51 ;5.69 ;2.77 ;TABLE 3 ;: 2.5mm Primary Nozzle with Adjuster ;Pressure (kPa) ;Flow (1/min) ;Hot/Cold ;Hot/Cold ;Hot ;Cold ;Mixed ;Flow Ratio ;15/520 ;8.19 ;8.15 ;16.34 ;1.00 ;7.93 ;6.97 ;14.90 ;1.14 ;7.66 ;5.89 ;13.55 ;1.30 ;7,13 ;4.98 ;12.11 ;1.43 ;6.73 ;4.07 ;10.80 ;1.65 ;5.97 ;3.07 ;9.04 ;1.94 ;5.56 ;2.59 ;8.15 ;2.15 ;4.99 ;2.07 ;7.06 ;2.41 ;15/280 ;5.82 ;5.67 ;11.49 ;1.03 ;5.75 ;4.81 ;10.56 ;1.20 ;5.20 ;4.20 ;9.40 ;1.24 ;5.08 ;3.59 ;8.67 ;1.42 ;4.88 ;3.10 ;8.19 ;1.67 ;4.40 ;2.55 ;6.95 ;1.73 ;4.28 ;2.12 ;6.40 ;2.02 ;4.19 ;1.60 ;5.79 ;2.62 ;TABLE 4 : 40 °C Mixed Flow at 15/520 kPa Supply Pressure ;Hot/Cold Inlet Hot/Cold Mixed Flow at 40#C (1/min) ;Temperature Flow Ratio 2.15 F 2.3 A 2.5 A ;65/15 1.0 11.7 14.0 16.3 ;65/10 1.2 12.8 14.0 14.3 ;60/15 1.3 13.2 13.3 14.0 ;60/10 1.5 9.3 11.7 11.5 ;55/15 1.7 8.1 10.6 10.7 ;55/10 2.0 6.9 9.0 8.8 ;50/15 2.5 6.0 6.8 6.6 ;TABLE 5 i 450*C Mixed Flow at 15/280 kPa Supply Pressure Hot/Cold Inlet Hot/Cold Mixed Flow at 40°C (1/min) Temperature Flow Ratio 2.15 F 2.3 A 2.5 A 65/15 65/10 60/15 60/10 55/15 55/10 50/15 1.0 1.2 1.3 1.5 1.7 2.0 2.5 8.1 8.9 9.1 9.3 8.1 6.9 6.0 9.9 10.9 10.0 8.9 8.2 6.9 5.8 11.3 10.5 9.4 8.4 7.4 6.4 5.9 -