Energy utilisation in commercial bread baking

The aim of this project was to benchmark energy utilisation of bread manufacturing and to provide methodologies and results with the aim of improving efficiency in commercial bakeries. The bread industry is an important provider of staple food products across the world. Owing to the large energy use in bread manufacturing, bakeries have come under increased scrutiny to reduce their environmental impact. The proving process exposes dough to heat and humidity in order to encourage yeast activation. Provers (responsible for 5 % of carbon emissions in bakeries) are over-engineered to the extent that energy costs impact upon performance. The industry standard practices that use large volumes of airflow to maintain food safety have not been scientifically justified. Experimentally validated Computational Fluid Dynamics (CFD) simulations showed the residence time distribution profiles for different numbers of air changes. The results have indicated that it is possible to reduce airflow by 33 % and electricity demand by over 70 %. A system-level thermodynamic analysis was developed in order to measure and model heat streams in industrial bread ovens. The model was subjected to a sensitivity analysis to ensure the calculations could be trusted to give suitably accurate results. A number of measurement techniques were employed and the methodology was designed to increase the potential for industry-wide use to assess the efficiency of ovens. The results showed that between 40 and 49 % of heat is wasted in industrial ovens. The model has been successfully distributed to industry. Experimental measurements of heat transfer for a range of regimes used in baking ovens were undertaken. The results were validated by previous correlations published in literature. Investigation focussed on three particular novel research areas. Firstly, comparisons between nozzle types showed that rows of circular jets could be approximated as slot nozzles for mean heat transfer. Secondly, the ratio of convective to radiative heat transfer was investigated. Thirdly, the prevalence of secondary peaks in local heat flux profiles was compared for two nozzle sets. These unique results can be used to help design baking ovens with energy efficient operating conditions