1. if the "stuff" floating didn't come from the air (open top) its debris that was previously caught in the evaporator (one of the reasons I mentioned to hose it down). A filter will of course cutdown the flow. Ideally you keep the pump matched to the resistance in the loop at the flowrate that gives youy the best performance. So the less resistance the better. A more powerful pump adds more energy to a loop, a very small amount as direct heat, the majority as kinetic energy, but both impact the lowest temperature your able to maintain.
2. Just placing the rad into the cooler will be a less than ideal heat transfer solution, ideally (given what your working with) the return from the computer would be on one side and the pump on the other forcing the flow to move through the evaporator
(The ideal solution is a heat exchanger with the rerigerant on one side and the water on the other, convoluted coil like a wort chiller or a plate heat exchanger being another approach, that of course means recharging the system ect)
3. Regulating the water temperature to avoid condensation is far easier said than done, to begin with room temperature is but one variable, the others are barometric pressure, relative humidity and the temperature of the block (which changes with the ambient temprature cooling the condenser)
The dew point moves around on you. Trying to get sensors that will compute that then compare the temperature of the block and turn the AC on and off is the exceptionally hardway to try to solve the problem.
Insulate the blocks to prevent condensation.
but just to illustrate the point
Quote:
Psychrometric Chart
The psychrometric chart gives the relative humidity for a given wet-bulb and dry-bulb temperature. To use, find the vertical line for the dry bulb temperature at the bottom of the chart, and the slanted line for the wet-bulb temperature at the curved top-left edge. Find the intersection point of these two lines, and read the percent relative humidity from the curved lines nearest that point.
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if you want to try to do it manually
Id recommend a cheap weather station with Relative humidity, temperature and barometric pressure
and a demo of
http://www.megawatsoft.com/humidair.asp?cat=5
if the block drops to the dewpoint temperature (for the given dry bulb temperature, relative humidity and barometric pressure), you have condensation
(hmmm... the demo has just one preset barometric pressure
)
example (at 8bar)
room temp (dry bulb) 70F
relative humidity (RH%) 40%
dew point 44.5F (block hits that you get condensation)
room temp (dry bulb) 70F
relative humidity (RH%) 70%
dew point 59.7F
room temp (dry bulb) 70F
relative humidity (RH%) 98%
dew point 69.4F
again
room temp (dry bulb) 90F
relative humidity (RH%) 40%
dew point 62.3F
room temp (dry bulb) 90F
relative humidity (RH%) 70%
dew point 78.8F
room temp (dry bulb) 90F
relative humidity (RH%) 98%
dew point 89.3F
of course 8bar is kind of useless (its a demo after all) that works out to some 236 inches of mercury
where I am its currently 29.77 in
(with a dew point of 14F, 14% RH, and 62F dry bulb)
so the "air" pressure in my examples would be like 8 times "standard" or about 267 feet underwater
the chart above is a "standard" atmosphere (29.92 inches of mercury (Hg) or 1.01 bar or 14.6 psi absolute)
finding a weather service that provides your dewpoint might be a better approach to do "manual" control
that of course assumes your exterior temp matches your interior
if its "dry" where you are you'll likely be OK with quite a decent subambient potential,
if on the other had its "muggy" youre screwed if you drop just a little below ambient