Your friction factor is not that high. It is just that the formula you use does not accurately calculate the required water temperature. Assuming everything is at room temperature, the formula is ((end_temperature - friction_factor) * total_weight - (total_weight - water_weight) * room_temperature) / water_weight.

Plugging in some numbers (metric), assume the total weight is 1600g, water weight is 500g, room temperature is 22 and your desired end temperature is 25, and a friction temperature of 3.5, then ((25 - 3.5) * 1600 - (1600 - 500) * 22)/500 = 20 which is what you measured for your water (3.5 c difference is 6.3 f). This makes much more sense than 20f (or 10c)

• Reply