Temperature profile on a continuous moving surface subjected to a constant heat rate in a horizontal channel

Abstract

This paper presents a theoretical analysis of the surface temperatures on conveyor borne materials in a typical manufacturing process, such as the preheat section of a PCB assembly line. The conveyor and materials are modelled as a continuous surface moving at a constant speed in a heated channel. The parameters studied include speed of the conveyor, the heat input rate and air flow over the surface.For problems of this nature, radiation interchange between the enclosed surfaces is significant in distributing the heat input, and losses due to radiation from the open ends of the channel may also account for about 15% of the total heat input. Often the airflow is only a small extraction flow, of about 0.2 m/s or less, to remove any toxic vapours, so that heat removal through convection is less important. The results show that, even for low conveyor speeds of 0.015 m/s or less, the heat outflow as a result of storage in the moving conveyor is the most significant portion, about 80% of the heat input. The temperature profile on the conveyor surface is then almost linear with maximum temperatures at the exit and is essentially proportional to the heat input rate. With a stationary surface, very high temperatures around the middle of the channel are observed.