Abstract
An innovative vacuum pan tube has been developed, tested, trialed and commercialized; it provides an alternative solution for increasing the capacity at a significantly lower investment when compared to the market equivalents. This technology has been in operation in numerous vacuum pans, some for several seasons, and the benefits to vacuum pan throughput are significant. The dimple tube technology was developed over a four-year period, from an initial concept through to its commercialization, and it has been through a series of analyses, alterations, tests and trials. These analyses included Computational Fluid Dynamics (CFD) to predict its flow and performance characteristics, Finite Element Analysis (FEA) to analyze the direct and fatigue stresses, pressure testing, non-destructive testing, in-service trials and laboratory testing. Manufacturing equipment and systems have been designed, developed and implemented as part of the commercialization process, in order to ensure the reliable and repeatable production of the technology, which has been taken from a concept, through to a commercially available and value-adding product. The outcome is a new tube technology that increases the heating surface area of an existing vessel by approximately 15%. The performance benefits of the additional heating surface area are as expected, but the increased turbulence makes a significant difference to the heat transfer coefficients, resulting in a significant increase in the evaporation rate and an increase in the throughput. The trial operation has shown no drawbacks or compromises to the existing operations. Retrofitting to the existing vessels is as simple as a retube of the vacuum pan. Due to the improved heat transfer coefficients when utilizing the dimple tube technology, rigorous lab-scale tests and full-scale trials have also shown that the tubes provide the opportunity to utilize lower grade steam to achieve the same heat transfer, enabling energy savings in the factory. Keywords: vacuum pan, tubes, heat transfer, turbulence, continuous vacuum pan, batch vacuum pan, dimple tubes, energy savings
