Five ThermoChill radiators were tested to ascertain their air and liquid side flow resistances, and to determine their heat dissipation characteristics. Additional data was also developed to describe the effect on flow resistance of different connecting fittings and to illustrate the effect of different coolant to air temperature differentials. A variety of fans were tested to enable users to obtain an insight as to their expected performance and to quantify the benefit of using two fans in a push-pull arrangement.

The radiators tested were the HE 80.1, the HE 92.1, and the HE 120 series; being the HE 120.1, HE 120.2, and HE 120.3. The latter three being the same core but lengthened to accommodate one or two additional 120mm fans.

As their names imply, the radiators are sized to fit the fan of that size; the HE 80.1 width being just slightly larger than the fan at 82mm, with the bottom extending 22mm and the top 28mm. The others are slightly wider than the fans, extending 9mm on either side for the HE 92.1 and 2mm for the HE 120 series. The top and bottom extended lengths are also slightly longer being 34mm and 26mm for the HE 92.1 and 29mm and 26mm for The HE 120 series.

The connections are female 3/8” BSP, which has a 1 thread per inch difference as compared to NPT. BSP barbed fittings are available in the US, though not common, but both metal and plastic NPT sealed without difficulty. Worth noting is that the connectors are machined from brass and quite stout.

Three radiators were tested comprehensively: The HE 80.1, the HE 92.1, and the HE 120.2; while all were tested for liquid side flow resistance and dissipation with selected fans of the low, medium, and high flow types.

Coolant flow rates were measured with a Danfoss MAG 5000 flow meter with the MAG 1100 ¼ in. magnetic flow tube, differential pressures with a Foxboro 823DP differential pressure transmitter and Digitek digital gauge, temperatures with a Fluke 2180A Digital RTD Thermometer with multipoint RTD selector, and the coolant temperature maintained with a Haake A82 Recirculating Chiller.

The coolant flow rate set points were 1.1, 1.9, 3.8, 5.7, 7.6, 11.4 lpm (0.3, 0.5, 1.0, 1.5, 2.0, and 3.0 gpm); and the air flow was set on the basis of the radiator backpressure at 3.7, 12.5, 37.4, and 62.3 Pa (0.015, 0.05, 0.15, and 0.25 in. H2O).

The air flow was generated with a voltage controlled blower assembly, and quantified by calculation using a Kunz 441S thermal anemometer. Air pressure was measured using a Energy Conservatory digital low pressure differential manometer.

The coolant to air temperature difference (“C” as defined below) used for this testing was 5.0°C, representative of a very well designed watercooling system with considerable ‘excess’ radiator heat dissipation capability. This is a very important distinction as a radiator’s heat dissipation is directly related to the temperature difference between the air and liquid sides. It will be shown that the coolant flow rate will slightly affect the heat dissipation, and that the air flow rate will strongly affect it; but the temperature difference is the defining parameter.

The following equations were used to calculate the radiators’ performance from the collected data:

For thermal resistance, or C/W (having the units °C/W):

where W = Watts
m = mass flow rate, kg/sec
Cg = specific heat capacity,
for H20, 4186 J/(Kg°C)

This reduces to:

Bill Adams