So if I have a tubular reactor for nanoparticle synthesis (PTFE tubes ID:2mm). The tubes are heated in a furnace. liquid Reagents at room temperature are pumped by a syringe pump and directed toward the furnace. The reagents decompose to form nanoparticles once they reach the steady-state furnace temperature. How can I estimate how long it takes for the reagents to to reach the set temperature in the furnace once they enter the furnace?