The thermometer should not touch the sides of the glass, and if it does it should be clamped in such a way that it no longer touches.
Cite this chapter Thome, J.
The inverted capillary tube acts as a reservoir to trap the compound's vapors.
It is analogous to a distillation setup, with the main difference being the vertical placement of the condenser.
The flow velocity in a core can be very high causing very high turbulences.
What does your instructor want you to accomplish? There are also different correlations that describe the heat transfer.