Experimental and multiscale numerical study of air-flue gas heat exchanger in a biomass boiler

This chapter presents an experimental study of air-flue gas heat exchanger inserted in a biomass boiler. This heat exchanger is used to supply hot air to an engine of a biomass micro-cogeneration unit. The heat recovery from the flue gases can be applied to different energy processes such as the heating or the transportation. Experimental measurements of air and wall temperatures at different positions in the air-flue gas heat exchanger are compared with the results obtained by 0D dynamic model. This model uses some results of a CFD modeling such as the calculation of the heat convection coefficient. Based on the direction of the air and the flue gas in the heat exchanger, three zones are observed: a counter-flow zone, a cross-flow zone, and a coflow zone. A good agreement is observed between the results obtained by 0D dynamic model and experimental results for the different zones.