Numerical and experimental analysis of a heat exchanger for new generation helicopter applications

The oil allows to lubricate and cool down several gearbox components that are fundamental for lift and forward flight of helicopters. The heat exchanger is the component designed to reduce the temperature of coolant fluid (oil) to preserve the functionality of helicopter gearbox components. In particular, the plate and fin heat exchanger enables rapid reduction of oil temperature by air cooling by leveraging its large heat exchange area. This type of heat exchanger are the most used in helicopter design thank to their compactness and simplicity allow to maximize thermal exchange with a lightweight configuration. However, a model to predict and characterize the performance of plate and fin heat exchanger is up to now not complete available and validated. In this work, a model based on Effectiveness-Number Transfer Units (-NTU) algorithm was developed. Exploiting the approximation of average fluids thermodynamic properties for zero dimensional (0D) design, we permit to provide a fast, scalable and detailed model for a rapid design and experimental validation for air-oil, counterflow, plate and fin heat exchanger. In particular, our model allow to estimate several parameters of oil cooling system including heat load, fluids temperature and heat exchanger efficiency. To evaluate our model performance, it was validated using a several data sets both published and unpublished experimental data. Our model predicts the results with a relative deviation less than 10% compared with the experimental data. Overall, by providing a novel set of equations for a plate and fin heat exchanger our work will allow to minimize the size of heat exchanger to achieve the maximum required heat load. This, in turn, enable to design smaller and lightweight heat exchanger with improved performances to achieve new generation helicopter gearboxes requirements.