High temperature jacketed piping: Review of the suited thermal models and comparison with experimental results

A comparison is presented between a theoretical model and the experimental data of the thermal performance of a jacketed pipe which belongs to an experimental facility aimed at testing the critical components of the externally fired combined cycle (EFCC) technology. The pipe consists of two concentric tubes, the inner with hot air (nominal conditions above 1000 °C) and the outer with cold water, whose function is to make the inner tube wall temperature to be tolerated by a traditional steel (e.g. an AISI series stainless steel). A proper model is identified to calculate the fluid temperatures at the pipe exit, by considering a spatial discretization of the system, such that on each resulting section a differential equation is iteratively solved which gets as boundary conditions the output values arising from the preceding section. The model predictions are compared to the data coming from an experimental facility, resulting in a good agreement: about 87% of the air side (and 92% of the water side) experimental data is falling within a ±8% deviation band from the expected values. Such difference is widely acceptable, being probably due to the uncertainties connected with to the use of closed-form correlations for calculating the convective heat transfer coefficients.