URTHER DEVELOPMENT OF A COMPUTER PROGRAM SIMULATING HEAT PIPE FUNCTIONING IN CONDEBELT PAPER DRYING

ABSTRACT

A previously developed computer program for depicting the heat and mass transfer behavior of heat pipe conduits, slightly open to a large ambient at their far ends, inside moist paper webs is developed further. The addition consists of accounting for the thermal dynamics of a hot metal slab from which the latent heat of evaporation corresponding to vapor generation in the hot end of the heat pipe is drawn. Values are used for the input parameters representing as closely as possible an approximately 40 % dry (by total weight) printing paper sheet being suddenly pressed against a hot steel or iron slab at l50°C or 200°C. These are conditions that could occur in Condebelt drying. Temperature distributions in the metal and inside the web, as well as the pressure distribution inside the web, are determined as functions of the distance from the hot surface and time. Important parameters are the initial metal and web temperatures, the interface Biot number, the structural geometry of the web, and the metal Fourier number. It is shown that there is a S to 25°C metal surface temperature drop in the first 100 μs after contact with the web. This can be significant in reducing possible web surface damage.