Abstract
The results of field measurements conducted in the Umka Cardboard Mill hall indicate a certain potential for heat recovery (approx. 4430 kW) in the air accumulated below the hall ceiling and extracted by the ventilation system. Analytical investigation is carried out for finding out the most favourable locations for heat exchangers' intake connections. Heat exchangers are to be used for waste heat recovery. Focus is laid on determining the convection flow rates along the vertical surfaces of the machine, as well as on defining the characteristics of the thermal plumes created above the machine. These characteristics are calculated according to the plume theory, introducing a virtual point source instead of the real source dimensions. The results of mass and heat balance of the hall are also presented in the paper. The same method can be applied in other paper mills and similar industry premises, where large flat machine surfaces are common. The investigation confirms the assumption that the plume formed above the heat exchangers in the coating drying section is the hottest and with considerable high airflow rate (6720 m3/h above the hottest heat exchanger). It reaches the ceiling level and spreads horizontally, penetrating the nearby sections along the hall. Therefore, it is suggested that this airflow is the most suitable for heat recovery. Copyright © 2010 John Wiley & Sons, Ltd.