by Ray Clark and Henri Azibert, A. W. Chesterton Company

The Fluid Sealing Division of A.W. Chesterton Company is using FLUENT to help study and more fully understand the effects of flow behaviour on the design and operation of mechanical seals. These types of seals are used extensively in a wide variety of industries to prevent leakage from fluid handling equipment such as centrifugal pumps and mixers.

As part of an ongoing development of new products, FLUENT is being used to explore ways of improving the heat removal efficiency of cooling systems commonly associated with dual mechanical seals. Figure 1 illustrates a typical pump/seal configuration in which pressurized fluid circulates through the seal forming a barrier to prevent leakage of the process fluid. Another function of the temperature-controlled barrier fluid is to remove frictional heat generated at sliding interfaces between rotating and nonrotating elements.

Centrifugal pump mechanical seal showing the barrier fluid (translucent blue) flow domain. Stationary (red) and rotating (blue) seal rings or faces are also depicted. Barrier fluid circulates into and out of the seal through two ports, one of which is visible in the figure.

An important finding of the present study is that axial circulation of fluid in the narrow annular spaces between the flow channel and the warmer interface regions of the seal can be substantially improved simply by tapering the bounding surfaces of the stationary seal faces and the shaft sleeve as shown in Figure 2. The patented surface tapering design provides maximum fluid circulation and a 50% increase in heat removal, a FLUENT prediction which has been verified by laboratory testing.

The Data Explorer visualization software was used for postprocessing of the FLUENT results. Information about A.W. Chesterton Company is available at http://www.chesterton.com.

Vectors, colored by temperature, show the barrier fluid circulation pattern at the 6 o'clock position midway between inlet and outlet. Modelling shows that the tapered-surface design contributes an axial component to the flow, which propels the fluid away from the central channel region toward the ends of the domain where fluid sealing and heat generation occur.

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