The main part of cooling and freezing is within food applications. MPG or 1,2-MonoPropylene Glycol is perhaps the most commonly used heat transfer fluid in those applications. Comparison between Temper and MPG has been done from freezing point of -40°C to -10°C. Below -40°C the viscosity of MPG gets too high for practical use. Already @ -30°C, the viscosity is so high that the centrifugal pumps barely can be used. A thumb rule is that at kinematic viscosity above 300 cSt, centrifugal pumps cannot be used. Other types of pumps are very expensive and inefficient. The calculations (Reynolds number, pressure drop and heat transfer coefficient) are made for circular tubes.