Heat and mass transfer processes in incandescent lamps and development of gas mixtures for their filling

Abstract

A model of a working gas medium for incandescent lamps (ILs) is described. Within the framework of the molecular-kinetic theory, with the help of Langmuir's concept of a stagnant layer about the incandescent tungsten filament, the mathematical model of heat and mass transfer processes for quasistationary operating conditions of the IL was formulated. In this case, the thermodiffusion contribution to tungsten mass transfer and temperature-dependent transfer coefficients of a working mixture were taken into account. With the solution of the transfer equations, the design formulas for the integral heat flux (loss) from the incandescent body and the integral mass flow of tungsten atoms through a filling gas in the IL containing a cylindrical (spherical) incandescent body were obtained. Based on the calculated heat losses from the incandescent body and mass transfer speed of the tungsten atoms in different gas media, effective compositions of multicomponent filling mixtures (N 2 -Ar-Kr and N 2 -Ar-Kr-Xe) are developed for commonly used bispiral krypton general-purpose ILs. Their applications allow the reduction of the cost of the lamps, while the luminous efficacy and the operating life of the lamps are the same as (or better than) those of lamps with the standard filling mixtures, N 2 -Kr.