lrrowe wrote:I do not remember enough of my old physics classes to start to approach this question.
With all other conditions remaining equal, is it better to move air over the fins of the raditor faster or slower?
I have found fans that move 60, 80, or 100 CFM. Is there an optimum air flow? Or are there many other variables to think about? Such as overall surface area of the radiator, depth of the fins, number of fins, amount of surface area that the fan covers and so forth? This sort of goes along with the speed of the heated water through the raditor.
Or for we camper's needs, is it adequate to use a combo that someone says gives good results and let it go at that. More of a trial and error approach?
MtnDon wrote:My bad.... That night the outside temperature dropped to 41, the interior was at 72. That was with the water heater set at medium, and the pump and fans running continuously. A difference of 31 degrees.
Last night I set the water heater to the lowest setting and let it run all night. The outside low was 36. The interior temperature was 64 degrees, a difference of 28 degrees. Again, the pump and fans ran continuously.
... I need to dig out another fan set. These are 45 CFM; I have one that moves 90 CFM, with a little more noise, but still quieter than the pump. I ordered a second unit so I will change them out and run a test with them mounted in a pair in place of the first set. It is scheduled to arrive next Thursday as are the temperature controller and my new IR thermometer. A higher rate of air flow through the radiator should put more heat into the trailer interior.
My approach to this is start with simple basic equipment and then make changes driven by what is observed.
Thoughts? Comments?
Any idea what the difference in water temp was in the water heater at the different settings?
Personally this looks like a successful test to me. What expectations do you have that these results don't meet?
MtnDon wrote:An electronic speed control, rather than a rheostat. Rheostats waste power as heat. A PWM controller is actually an electronic switch that turns the power on and off extremely rapidly, leaving it on for short or longer durations and as such does not waste so much. Theire is an operating loss but it is insignificant when compared to a rheostat.
ebay has a bunch
I'm thinking that a speed controller might be handy if the fan used had a high enough volume to make slowing it down worthwhile.
I'm also beginning to wonder if there are some small squirrel cage fans in 12 VDC that might be better suited than the axial flow computer cooling fans? I have not looked. The nice thing about computer fans is their low current draw. That comes with lower flow and lower ability to push air through an obstruction like a radiator.
lrrowe wrote:Shadow Catcher,
How does one measure air flow?
MtnDon wrote:Perhaps there has been some recent change but the manual for our 6 gallon pilot light Suburban water heater states, on page 12... "CAUTION: Temperature setting on control was factory set at low (120F/49C) to reduce risk of scald injury. Setting the temperature dial past the low position will increase the risk of scald injury......."
There is a black plastic adjuster that has settings with Low at one end, Medium in the center and High at the other end of the quadrant range of movement. That does permit adjustment of temperature to quite high temperatures. That's for the basic pilot light model. I have no idea about the other models. Ican easily get the water hot enough to cook fish by immersion.
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