So... today, I got my gritty mittens on an IV kit (Braun Intrafix) (and a blood kit) in order to get a better view of the task at hand..
Initially, I wanted the system to handle both IV (such as saline) and blood, but the flow rates are of a concern to me. Even professional equipment rolls up about 1 m (!!!!) of tube in order to create enough heating surface to heat the liquid and they even struggle with the ambient cooling of the last length of tubing.
Further input was given from a nurse related to the daily use and problems. This lead me to redesign the heating block based on the specifications of the tubing:
Diameter: 4.1 mm
Max pressure : 2 bar (current solution is a gravity fed system, so this is not important)
Max temperature: 40 C
I had hoped on setting a higher temperature for compensating for the ambient temperature based on the thermal resistance of the tubing (adjusted by the software), but I'll have to limit the maximum temperature to below 40 C.