Improving the effectiveness of heat treatment for insect pest control in flour mills by thermal simulations

The aim of this study was the development of a method to improve the effectiveness of heat treatment (HT) for insect pest control in flour mills by thermal analyses and temperature trend models. Specific attention was paid to surface temperatures of thermal bridges (TBs), which represent HT weakness points because they provide refuge to insects and increase expenditure of electric power due to heat flux loss. Air and TB surface temperatures were monitored in a flour mill during execution of an HT. A first thermal analysis showed that values of indoor air temperatures near TBs were always lower than the computed temperature level that would also guarantee insect mortality on TB surfaces. Since the length of the steady-state air temperature profile was lower than that lethal to all insect vital stages, time series forecasting models based on trend analyses were used to simulate the suitable HT duration. The results highlighted that HT should be increased by 9 h to achieve an air temperature above 45 °C. Finally, to obtain TB surface temperatures lethal to insects, simulations were performed of building interventions capable of reducing sensible heat flux loss through the TBs by using insulating materials. The method described in this paper could help operators define a more suitable HT length and support flour mill owners in decision-making when building interventions to improve heat capacity of the mill envelope should be considered to reduce the power consumption of HT.