Computer processor cooling heat exchanger, computer fan, 3.8L/min 12V water pump.  Latex tubing, insulated box.  Use either warm water or ice water as conditions dictate.

 

The reason for this is twofold.  In the summer the mirror may be heat soaked from the heat of the day and cause tube currents because the air temperature drops faster than the mirror.  The mirror can take several hours to cool, and always lags warmer than the air until the air temperature stabilizes and the mirror catches up.  By cooling the mirror by blowing cold air on it the mirror can be brought down to a temperature below the air temperature so there are no tube currents.  Now it is probably true that the mirror will see some stresses as a result which will affect it's figure, but I'm also quite sure the view is better than with huge boiling air coming off the mirror.

 

The other case is in the winter, when the mirror may cool below the dew point.  Now it is true that a Newtonian telescope with the mirror at the bottom of a long tube is less prone to the mirror condensing moisture out of the air than an SCT's corrector plate right out there in the open, but it still does condense moisture.  Not dripping wet, but enough to degrade the view considerably.  In this condition, warm water can be pumped through the heat exchanger to warm the mirror and the tube just enough to keep it above the dew point.