JHZR2
Staff member
Originally Posted By: Jetronic
Originally Posted By: JHZR2
Figure the specific heat of oil is 2kJ/kg*K
Figure 6 quarts of oil weighs 4 kg.
Figure the heater has to heat the ambient (poor insulation and no guard heater), and the metal, so efficacy is maybe 30ish%.
So 50W going in means 50J/sec.
Every 20 sec maybe 1kJ.
Need 8+ kJ to raise 1 Kelvin.
So 1K every 160 secs.
So after 1 hr around 20K, which is a factor of 9/5 so 38ishF? Seems about high but the engine thermal mass and losses are a total swag.
As it warms, delta T with ambient will increase so losses will go up until some steady state is obtained.
I'm scratching this at breakfast counter in a restaurant do someone can check my conversion and math.
6 quarts of oil is closer to 5 kg, so probably 20% less heat rise per hour than you calculations... didn't bother looking up te specific heat of oil (depends if it's PAO, gr V or dino anyway) but I'm sure the specific heat of the oil pan itself is 3 times higher than the oil it contains and could be another 3-5 kg...
I have to think that the difference between pao, ester, and hydro cracked lubes is minimal in terms of specifi heat. First, second decimal place? Could be wrong.
While the heater will certainly have to heat the pan and will dissipate in the x and y directions, the length scale in z is much shorter and should facilitate heat transfer preferentially into the oil. This is doubly so given that heat spread in c and y will continually shed energy in z as the oil further and further out is cold. Conduction all the way to the block I'd argue is viable, but secondary until heat transfer in z along the whole wetted surface drops below in plane conductivity. The rates do probably differ by an order of magnitude though...
Originally Posted By: JHZR2
Figure the specific heat of oil is 2kJ/kg*K
Figure 6 quarts of oil weighs 4 kg.
Figure the heater has to heat the ambient (poor insulation and no guard heater), and the metal, so efficacy is maybe 30ish%.
So 50W going in means 50J/sec.
Every 20 sec maybe 1kJ.
Need 8+ kJ to raise 1 Kelvin.
So 1K every 160 secs.
So after 1 hr around 20K, which is a factor of 9/5 so 38ishF? Seems about high but the engine thermal mass and losses are a total swag.
As it warms, delta T with ambient will increase so losses will go up until some steady state is obtained.
I'm scratching this at breakfast counter in a restaurant do someone can check my conversion and math.
6 quarts of oil is closer to 5 kg, so probably 20% less heat rise per hour than you calculations... didn't bother looking up te specific heat of oil (depends if it's PAO, gr V or dino anyway) but I'm sure the specific heat of the oil pan itself is 3 times higher than the oil it contains and could be another 3-5 kg...
I have to think that the difference between pao, ester, and hydro cracked lubes is minimal in terms of specifi heat. First, second decimal place? Could be wrong.
While the heater will certainly have to heat the pan and will dissipate in the x and y directions, the length scale in z is much shorter and should facilitate heat transfer preferentially into the oil. This is doubly so given that heat spread in c and y will continually shed energy in z as the oil further and further out is cold. Conduction all the way to the block I'd argue is viable, but secondary until heat transfer in z along the whole wetted surface drops below in plane conductivity. The rates do probably differ by an order of magnitude though...