Low order models have also been dev

Low order models have also been developed which attempt to predict the cooling performance that can be achieved in transpiration and effusion cooling geometries. One such example is provided in a 1994 study by Eckert and Cho [15]. In the study the authors present an idealised transpiration cooling model which assumes that the diameter and spacing of the pores is negligible. Additionally, several properties of the coolant and hot gas fluid streams are assumed equal such as density and thermal conductivity. An energy balance is performed permitting an estimation of the cooling performance of the transpiration system with the results compared to experimental data. The authors then developed the model to account for larger channels with great pitching of the film holes, more akin to effusion type systems. This development therefore permitted variations in the Stanton number to be identified at the hole exits and over the film cooled regions of the solid. Through an energy balance an approximate wall temperature could be ascertained. Further models for transpiration cooling have been developed for cooling in hypersonic applications, see for example [16]. The above papers provide a summary of several low order models developed for quasi-transpiration and transpiration type system. The present study demonstrates a low order analytical model for a double-wall system accounting for the various complex cooling mechanisms occurring. The construction of the model permits the addition and subtraction of further cooling mechanisms thus demonstrating the potential generality of the model. paper from 2003. Whilst the method uses CFD,the domain grid is relatively course due to the implementation of a sub-grid scale model (proposed by Luff and McGuirk [14]) resulting in individual pedestals not being resolved, but rather low order models implemented to simulate the pressure loss and heat transfer augmentation effects that arise from the pedestals. Whilst the model has some limitations, such as the inability to differentiate between staggered and inline pedestals, the qualitative performance of the model was verified with the authors concluding further experimental validation could aid in refining the method. Low order models have also been developed which attempt to predict the cooling performance that can be achieved in transpiration and effusion cooling geometries. One such example is provided in a 1994 study by Eckert and Cho [15]. In the study the authors present an idealised transpiration cooling model which assumes that the diameter and spacing of the pores is negligible. Additionally, several properties of the coolant and hot gas fluid streams are assumed equal such as density and thermal conductivity. An energy balance is performed permitting an estimation of the cooling performance of the transpiration system with the results compared to experimental data. The authors then developed the model to account for larger channels with great pitching of the film holes, more akin to effusion type systems. This development therefore permitted variations in the Stanton number to be identified at the hole exits and over the film cooled regions of the solid. Through an energy balance an approximate wall temperature could be ascertained. Further models for transpiration cooling have been developed for cooling in hypersonic applications, see for example [16]. The above papers provide a summary of several low order models developed for quasi-transpiration and transpiration type system. The present study demonstrates a low order analytical model for a double-wall system accounting for the various complex cooling mechanisms occurring. The construction of the model permits the addition and subtraction of further cooling mechanisms thus demonstrating the potential generality of the model.