This paper discusses the design, correction of data, and performance of a cylindrical test section prepared by inserting an electric cartridge heater into a hollow cylinder. The first part of the study presents a quantitative rule for the design of a test section providing the most uniform boundary condition for heat transfer experiments. The second part considers the effect of inactive zones in the cartridge heater on temperature and heat flux distributions in the test cylinder. The problem of circumferentially uneven heating by the cartridge heater is treated in the third part. A method is proposed to detect the degree of uneven heating, and formulas are derived to assess its influence on the boundary condition provided by the test cylinder during a heat transfer experiment. forced convection, instrumentation, measurement, techniques.