Hose

Abstract

A hose (200) is described, the hose comprising a first section (210) comprising a cross sectional area A.sub.χ and a second section (220) comprising a cross section area kj. The first section is in fluid communication with the second section and, in use, the first section is located upstream of the second section. Additionally, Axis at least twice the size of A2. Use of the hose and a method of dispensing slurry are also described.

Claims

1. A hose for use in the production of a building product from a gypsum slurry, the hose comprising: a first section comprising a cross sectional area A.sub.1, and a second section comprising a cross section area A.sub.2, said first section in fluid communication with said second section, wherein, in use, said first section is located upstream of said second section, wherein A.sub.1 is at least twice the size of A.sub.2, wherein said hose comprises a third section comprising a cross sectional area A.sub.3 located intermediate said first section and said second section, wherein said first section is connected to said third section by an elbow, wherein said first section comprises a longest dimension d.sub.1 in a plane perpendicular to its longitudinal axis, and wherein said elbow comprises an external radius of curvature at least half d.sub.1.

2. The hose of claim 1, wherein A.sub.1 is at most four times the size of A.sub.2.

3. The hose of claim 1, wherein A.sub.1 is the same size or larger than A.sub.3.

4. The hose of claim 1, wherein A.sub.1 is at most four times the size of A.sub.3.

5. The hose of claim 1, wherein the longitudinal axis of said first section lies generally perpendicular to the longitudinal axis of said third section.

6. The hose of claim 1, wherein said elbow comprises an external radius of curvature at most twice d.sub.1.

7. The hose of claim 1, wherein said second section comprises at least two subsections, with the total cross sectional area of said subsections being equal to A.sub.2.

8. The hose of claim 7, wherein the cross sectional area of each subsection within the plurality of subsections is substantially equal.

9. A method of manufacturing a gypsum product comprising: mixing a gypsum slurry in a mixer, exiting said gypsum slurry from said mixer through the hose of claim 1 on to a forming table, setting said gypsum slurry.

10. A method of dispensing a gypsum slurry including providing a hose with a plurality of distribution portions, where the hose comprises at least two sections with respective cross sectional areas A.sub.1 and A.sub.2, wherein the ratio of A.sub.1 to A.sub.2 is such that flow asymmetry in said distribution portions is below 1%.

11. The method of claim 10, wherein said method is a method of dispensing a gypsum slurry to produce a gypsum based product.

12. The method of claim 11 wherein said method comprises: providing a mixer, providing a forming table, and dispensing said gypsum slurry from said mixer through said hose on to said forming table.

13. The method of claim 10, wherein said method is a method of dispensing a gypsum slurry to produce a gypsum based product, and wherein said hose is the hose of claim 1.

Description

DETAILED DESCRIPTION

[0035] Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0036] FIG. 1 is an image of a prior art hose in use in the manufacture of a building product;

[0037] FIG. 2 is an image of a hose according to the present invention in use in the manufacture of a building product;

[0038] FIG. 3 is a graph illustrating the right/left flow heterogeneity of numerically modelled hose systems;

[0039] FIG. 4 is a graph illustrating the effect of varying the ratio of A.sub.1 to A.sub.2 on the modelled flow rate deviation;

[0040] FIG. 5 is a graph illustrating the effect of varying the ratio of A.sub.1 to A.sub.3 on the modelled flow rate deviation; and

[0041] FIG. 6 is a graph illustrating the effect of varying the external radius of curvature of the elbow section on the modelled flow rate deviation.

[0042] Turning first to FIG. 1, there is depicted a boot or hose 100 as is known in the prior art. As can be seen from the inset of FIG. 1, the hose comprises a first section 110 and a second section 120 comprising two subsections 121. The first section 110 and the second section 120 are in fluid communication, and the first section 110 is connected to the canister (not shown) of a tangential outlet mixer (not shown).

[0043] As can be seen from FIG. 1, the hose 100 is in use dispensing a gypsum slurry 160 on to a forming table 170 as part of a building product manufacturing process. Here the building product being formed is a lightweight plasterboard.

[0044] FIG. 1 further illustrates the uneven nature with which this prior art hose 100 dispenses the gypsum slurry 160 on to the forming table 170. The flow of gypsum slurry 160 from the right subsection 121 of the second section 120 is far greater than the flow of gypsum slurry 160 exiting the left subsection 121 of the second section 120, as can be seen by the distance the gypsum slurry 160 from each subsection 121 extends along the length of the forming table 170. The distance between the ends of the gypsum slurries extending from each subsection is marked as X.sub.1 on FIG. 1.

[0045] Turning now to FIG. 2, there is depicted a hose 200 according to the present invention. As can be seen from the inset of FIG. 2, the hose comprises a first section 210, a second section 220 comprising two subsections 221 and a third section 230 located between the first section 210 and the second section 220. Each of the first section 210, the second section 220 and the third section 230 are in fluid communication with one another, and the first section 210 is connected to the canister (not shown) of a tangential outlet mixer (not shown). The hose further comprises an elbow which connects the first section 210 to the third section 230.

[0046] As can be seen from FIG. 2, the boot or hose 200 is in use dispensing a gypsum slurry 260 on to a forming table 270 as part of a building product manufacturing process. Here the building product being formed is again a lightweight plasterboard with the same formulation as was used to produce FIG. 1.

[0047] As opposed to FIG. 1, FIG. 2 illustrates that the hose 200 dispenses the gypsum slurry 260 far more evenly across the forming table than the prior art hose 100 of FIG. 1. Whilst the flow of gypsum slurry 260 from the right subsection 221 of the second section 220 is still greater than the flow of gypsum slurry 260 exiting the left subsection 221 of the second section 220, the difference between the two subsections 221 is greatly reduced. Length X.sub.2 is far less than length X.sub.1, indicating hose 200 greatly increases the uniformity of flow through the two subsections 221.

[0048] Whilst hose 200 has a clear advantage over prior art hose 100, the two hoses differ from one another in a number of design features. As such, to isolate the design features that contribute the improved flow characteristics of the hose 200, numerical modelling was undertaken.

[0049] Numerical Modelling

[0050] A Base Model

[0051] To ensure a reliable data, as a first stage numerical models were developed to replicate the physical results observed in FIGS. 1 and 2. With this aim, numerical modelling was undertaken using a continuous one-phase model using the ANSYS Fluent computational dynamics software package. Within the framework of the model, the foamed gypsum slurry used in the trials depicted in FIGS. 1 and 2 was modelled as an effective incompressible fluid with a non-Newtonian rheology. Additionally, the rheological law used in the model was Herschel-Bulkley rheology, with the coefficients used in the model based upon experimental measurements performed with a lab rheometer

[0052] Additionally, to replicate the trial conditions use to produce the images of FIG. 1 and FIG. 2, the numerical model focuses on a system using a tangential outlet mixer and a canister. In such a system, a rotational flow component is introduced to the gypsum slurry by the canister. In alternative systems where a bottom outlet mixer is used, the mixer itself is responsible for a rotational flow component in the gypsum slurry as it enters a hose. As such, whilst the numerical models discussed herein focus on the use of a tangential outlet mixer, the results also hold for bottom outlet mixers as both mixer variations introduce equivalent rotational components into the flow of a gypsum slurry within a hose.

[0053] To compare the effect of the prior art hose 100 of FIG. 1 with the hose 200 depicted in FIG. 2, both were modelled and simulations completed. The results of these simulations are depicted in FIG. 3.

[0054] FIG. 3 depicts the heterogeneity of the flow exiting the right and left subsections in both the prior art hose 100 and the hose 200 of FIG. 2. When calculating the heterogeneity of the flow rate, the flow rate though each subsection was calculated using the equation below:

Q.sub.Slurry=∫.sub.Ωu.sub.tdΩ

where u.sub.t is the local velocity transverse to the cross-sectional area and Ω is the integration area of the cross-section. The right/left heterogeneity was then determined as a percentage difference between the left and right subsection flow rates.

[0055] As can be seen from FIG. 3, the numerical model was successful in replicating the results seen during use of the prior art hose 100 and the hose 200 of FIG. 2. As a baseline model had been successfully established, a parametric study was conducted to isolate the features of the hose 200 which produced the observed reduction in flow rate heterogeneity.

[0056] Parametric Study

[0057] Within the parametric analysis, the prior art hose 100 seen in FIG. 1 was taken as a baseline. Various dimensions and features of the prior art hose 100 were varied individually and in turn to isolate those which affected the right/left heterogeneity of the hose.

[0058] During the course of the parametric study, the following features were determined to affect the right/left heterogeneity of the hose.

[0059] First Section and Second Section—Ratio of Cross Sectional Areas

[0060] The parametric study revealed that the ratio of the cross sectional area of the first section (A.sub.1) to the size of the cross sectional area of the second section (A.sub.2) had the greatest influence on the right/left homogeneity of the hose. In these calculations, A.sub.1 was taken to be the total cross sectional area of the first section. A.sub.2 was taken as the total cross sectional area of the second section, in this case the sum of the cross sectional areas of both subsections of the hose.

[0061] As can be seen in FIG. 4, improvements in the right/left heterogeneity can be seen when the ratio of A.sub.1 to A.sub.2 reaches one. However, the greatest improvement in right/left heterogeneity can be seen when the ratio of A.sub.1 to A.sub.2 is two or above.

[0062] The ratio of A.sub.1 to A.sub.2 has a very strong effect on the right/left heterogeneity of the hose, and controlling this ratio alone is sufficient to reduce the right/left heterogeneity of a hose to an acceptable level. From an analysis of the numerical data, the Applicant hypothesises that the reduced heterogeneity seen when the A.sub.1 to A.sub.2 ratio is increased is due to the creation of a recirculation zone within the hose. The Applicant believes this recirculation zone disrupts the rotational component of the flow of the gypsum slurry as it enters the hose. This disruption of the rotational component of the fluid flow is effective in reducing the vorticity of the gypsum slurry, whatever its source: either directly from the mixer (as in a bottom outlet mixer) or as a result of the canister (as in a tangential outlet mixer). As such, increasing the ratio of A.sub.1 to A.sub.2 improves the homogeneity of flow exiting the hose for both tangential outlet and bottom outlet mixers.

[0063] First Section and Third Section—Ratio of Cross Sectional Areas

[0064] The parametric study further revealed that the ratio of the cross sectional area of the first section (A.sub.1) to the size of the cross sectional area of the third section (A.sub.3) also influenced the right/left homogeneity of the modelled hose. In these calculations, A.sub.1 was again taken to be the total cross sectional area of the first section. Additionally, A.sub.3 was taken to be the total cross section area of the third section.

[0065] The parametric study revealed, as illustrated in FIG. 5, that improvements in the right/left homogeneity of the modelled hose are seen when the ratio of A.sub.1 to A.sub.3 reaches one. A more dramatic improvement in the right/left homogeneity of the modelled hose can be seen when the ratio of A.sub.1 to A.sub.3 lies in the range two to three. Finally, the numerical modelling undertaken indicated that the right/left homogeneity of the modelled hose decreased again once the ratio of A.sub.1 to A.sub.3 exceeded four.

[0066] Whilst the controlling the A.sub.1 to A.sub.3 ratio has a strong effect on the right/left homogeneity of the hose, controlling this ratio is not as powerful as controlling the A.sub.1 to A.sub.2 ratio. From an analysis of the numerical data, the Applicant hypothesises that the changes in the right/left heterogeneity observed when varying the A.sub.1 to A.sub.3 ratio are the result of variations in the recirculation seen in the elbow of the hose. As previously discussed, the gypsum slurry entering the hose from the canister of a tangential mixer has a rotational component to its flow. The same is also true if the gypsum slurry enters the hose directly from a bottom outlet mixer.

[0067] Where A.sub.3 is smaller than A.sub.1, or the same size as A.sub.1, the gypsum slurry flow generates vorticity when it encounters the restriction of the third section. Within the range highlighted in FIG. 5, the Applicant believes this vorticity effectively counteracts the rotational component of the gypsum slurry as it enters the restriction, resulting in a well-balanced flow. Where the ratio of A.sub.1 to A.sub.3 increases beyond that highlighted in FIG. 5, the right/left heterogeneity increase again, apparently due to the large change in cross sectional area upon entry into the third section introducing its own rotational component to the flow.

[0068] The Elbow—External Radius of Curvature

[0069] Certain embodiments of the present invention include an elbow or transition which either (1) connects the first section to the second section, where there are only two sections, or (2) connects the first section to the third section, where there are three sections. In these embodiments, the elbow has a direct influence on the right/left heterogeneity of the hose.

[0070] The shape of the elbow, and the transition between the first section and the third section, can be described by the elbow's external radius of curvature R.sub.Ex. The external radius of curvature of the elbow is measured as the maximum radius of curvature of the elbow, as illustrated in FIG. 6.

[0071] Where the elbow was present, the parametric study revealed that modifying R.sub.Ex could improve the right/left homogeneity of the flow. These effects are also illustrated in FIG. 6. Where the first section was taken to have a longest internal dimension in a plane perpendicular to its longitudinal axis of d.sub.1, the numerical modelling undertaken illustrated that improvements in the right/left heterogeneity were seen when R.sub.Ex was equal to half d.sub.1. The numerical modelling undertaken indicates these improvements remained present where R.sub.Ex was equal to twice d.sub.1, before decreasing. These findings are illustrated in FIG. 6.

[0072] Again, the numerical model illustrates that controlling R.sub.Ex in relation to d.sub.1 has an effect on the right/left homogeneity of the hose. However, this effect is less pronounced than both varying the A.sub.1 to A.sub.2 ratio and varying the A.sub.1 to A.sub.3 ratio. Furthermore, the analysis conducted by the Applicant further suggests that controlling R.sub.Ex in relation to d.sub.1 has no effect on the right/left heterogeneity of a hose unless control of the A.sub.1 to A.sub.2 ratio has already introduced a recirculation zone into the hose.

[0073] The numerical modelling conducted by the Applicant suggests that the improvement in right/left heterogeneity seen in the range

[00001]$\frac{d_1}{2}\le R_{\mathrm{Ex}}\le 2d_1$

is due to the extension of the recirculation zone within the hose. This extension of the recirculation zone ensures the rotational component of the gypsum slurry flow entering the hose is broken before the gypsum slurry reaches the second section, increasing flow homogeneity.

[0074] Aspects, embodiments and features of the present invention may also be defined by the following clauses. [0075] 1. A hose for use in the production of a building product from a gypsum slurry, the hose comprising: a first section comprising a cross sectional area A.sub.1, and a second section comprising a cross section area A.sub.2, said first section in fluid communication with said second section, wherein, in use, said first section is located upstream of said second section, wherein A.sub.1 is at least twice the size of A.sub.2. [0076] 2. The hose of clause 1, wherein A.sub.1 is at most four times the size of A.sub.2. [0077] 3. The hose of clause 1 or clause 2, wherein said hose comprises a third section comprising a cross sectional area A.sub.3 located intermediate said first section and said second section. [0078] 4. The hose of clause 3, wherein A.sub.1 is the same size or larger than A.sub.3. [0079] 5. The hose of clause 3 or clause 4, wherein A.sub.1 is at most four times the size of A.sub.3. [0080] 6. The hose of any one of clauses 3 to 5, wherein the longitudinal axis of said first section lies generally perpendicular to the longitudinal axis of said third section. [0081] 7. The hose of any one of clauses 1 to 2, wherein said first section is connected to said second section by an elbow. [0082] 8. The hose of any one of clauses 3 to 6, wherein said first section is connected to said third section by an elbow. [0083] 9. The hose of clause 8, wherein said first section comprises a longest dimension d.sub.1 in a plane perpendicular to its longitudinal axis, and wherein said elbow comprises an external radius of curvature at least half d.sub.1. [0084] 10. The hose of clause 9, wherein said elbow comprises an external radius of curvature at most twice d.sub.1. [0085] 11. The hose of any one preceding clause, wherein said second section comprises at least two subsections, with the total cross sectional area of said subsections being equal to A.sub.2. [0086] 12. The hose of clause 11, wherein the cross sectional area of each subsection within the plurality of subsections is substantially equal. [0087] 13. A method of manufacturing a gypsum product comprising the steps of, [0088] mixing a gypsum slurry in a mixer, [0089] exiting said gypsum slurry from said mixer through the hose of any one of clauses 1 to 13 on to a forming table, [0090] setting said gypsum slurry. [0091] 14. A method of dispensing a gypsum slurry including providing a hose with a plurality of distribution portions, where the hose comprises at least two sections with respective cross sectional areas A.sub.1 and A.sub.2, wherein the ratio of A.sub.1 to A.sub.2 is such that flow asymmetry in said distribution portions is below 1%. [0092] 15. The method of clause 14, wherein said method is a method of dispensing a gypsum slurry to produce a gypsum based product. [0093] 16. The method of clause 15 wherein said method comprises: [0094] providing a mixer, [0095] providing a forming table, and [0096] dispensing said gypsum slurry from said mixer through said hose on to said forming table. [0097] 17. The method of clause 15, wherein said hose is the hose of any one of clauses 1 to 13.