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Show o Figure 5 : Effect of Excess Air on Thermal Performance Supporting Technologies & Techniques There are a number of techniques which have been used to support the development of new technologies, and produce improved system designs. Physical Modelling:- This is an experimental method mostly involving small scale isothermal models. An important feature of these models is the facility to view the interior so that the flows can be observ ed. The models used are not simply scaled geometrically, but are scaled using well established scaling and similarity criteria, to allow information about the flow fields or thermal performance to be obtained. Flow visualisation can be achieved with air or water as the fluid, with flow tracers being introduced to illustrate the characteristics of the flow. In order to illustrate the behavior of a reacting flow, the technique of acid-alkali can be applied. This technique can be used to visualise flame length and shape. This information is useful in that it can provide valuable thermal performance data which can be used in mathematical models. Mathematical Modelling:- Mathematical modelling, especially so-called zone-type models, has played a central role in the development, demonstration and acceptance of much of the gas-fired burners, boilers and furnaces illustrated above. The zone models have proved to be particularly robust in predicting furnace performance. They can provided valuable insights into improving plant performance, not just in terms of conventional thermal efficiency considerations but also, for example, calculating the fuel savings associated with different shift patterns, as indicated in Table 1. :-o - C • V I.CAO TEM°_HArLHE '250 C. TUHNACE OuTP'_* '^:"Kt,-/n •:GC toe 0 '0 2C % bX.CCSS ilR 30 |