Heat Transfer Performance of Propylene Glycol Versus Ethylene Glycol Coolant Solutions in Laboratory Testing

This paper describes the results of laboratory testing comparing the heat transfer performance of heavy duty radiators with Propylene Glycol and Ethylene Glycol based coolants. Solutions of 50/50 Propylene Glycol/ water (50/50 PG/water) and 50/50 Ethylene Glycol/water (50/50 EG/water) were tested in radiators of different geometries. The tests showed that the performance of 50/50 PG/water is degraded at higher flow rates to a greater degree than either 50/50 EG/water or 100% water. Specifically, it was found that in typical truck radiators the cooling performance of water drops off below 2.52 L/s (40 gpm), while that of 50/50 EG/water drops off below 3.78 L/s (60 gpm) and that of 50/50 PG/water drops off below 5.05 L/s (80 gpm). It is recommended that crossflow radiator designs be used for short, wide radiator applications to maximize the fluid flow rate in the radiator tubes.