Temperature separation of a gas is produced by the Hartmann-Sprenger (HS) tube worked by jet now issuing from a convergent nozzle. The effect of temperature separation depends on thermal effects of the HS tube. The coupling of a secondary resonator to the HS tube or the use of a convergent nozzle with thin rod laid along its axis changes operation mode of the HS tube and these can improve strength of oscillation in the HS tube and the thermal effect of it. In the present paper, effects of the secondary resonator and of the use of the nozzle with rod on the thermal effects are observed. Considering these effects, an apparatus of temperature separation is composed and its separation characteristics are investigated for various operation modes of the HS tube and for various sizes of hot-gas outlet. From experimental results, optimum operation mode and optimum size of hot-gas outlet for the efficiency of temperature separation are found.