Fig. 1. Internal structural diagram of temperature control box

Fig. 2. Temperature simulation results without fan

Fig. 3. Fan wind direction

Fig. 4. Simulation results for wind direction 1. (a) Temperature ; (b) flow-field

Fig. 5. Simulation results for wind direction 2. (a) Temperature; (b) flow-field

Fig. 6. Simulation results for wind direction 2 with box chamfer. (a) Temperature; (b) flow-field

Fig. 7. Seven temperature recording points

Fig. 8. Recording point temperatures under different heat transfer coefficients

Fig. 9. Real picture of temperature control box

Fig. 10. Schematic of TDLAS gas detection temperature control experimental system

Fig. 11. Temperature curves in temperature control box within one hour under different setting temperatures. (a) 36 ℃; (b) 38 ℃; (c) 40 ℃; (d) 42 ℃

Fig. 12. Second harmonic signal

Fig. 13. CO₂ concentration at room temperature and change of room temperature. (a) CO₂ concentration at room temperature; (b) room temperature

Fig. 14. CO₂ concentrations under different temperatures. (a) 36 ℃; (b) 40 ℃