Portable Water cooled Chillers

Hmm, depending on the sizing of the pump head, and the tubing connections, it may be that one pump is moving more gpm (Flow) or one was sized to make more efficient use of power. The short course is that the differences are probably in net cooling capacity and the more 'correct' unit more closely matches either your current cooling needs or perhaps your future needs (hopefully someone ran the analysis.) Unfortunately, the real answer might also be that you need two smaller units with them working in tandem on different areas of molds or 'lag loaded' together to match the demand needs in your plant environment and the various size molds and cooling requirements you might encounter depending on production rates and the temperature of your plant process water (depends on whether is recirculated or not).

To show a rough idea on the change in cooling capacity based on 'flow', try this simple experiment at your local gas station (assuming you are allowed to pump your own gasoline):

On a typical warm day, dispense the gasoline at a steady, slow to moderate rate into your tank, paying attention to the temperature of the gas nozzle assembly in the palm of your hand. Assuming the gas is stored in the ground it is likely that it is cooler than the ambient air (at around 56 degrees or so in the tank in the ground) the nozzle in your hand should feel 'cooler' in short order. This is because the cooler gasoline coming up from the ground as it flows by that point is pulling heat from the metal nozzle. Stop the process. After waiting a few seconds for the nozzle temperature to normalize again, dispense the gasoline at a much higher rate - and the nozzle should get colder quicker than in the first instance. The temperature of the gas from underground didn't change (still 56 degrees), but the amount of gasoline flowing by the point is pulling heat from the nozzle at the higher rate.

see these sites for some clarification on 'flow' versus cooling capacity and the importance of 'right sizing'

http://www.temperaturecorporation.com/loadsizing.htm

http://www.process-cooling.com/CDA/Archives/b306d426847b9010VgnVCM100000f932a8c0____

http://www.engineersedge.com/industrial-equipment/portable-chillers.htm

You are looking for cooling capacity and hopefully you have analyzed the system as a whole rather than get caught up on just one item 'cooling' - other topics to keep in mind are the 'turbulent flow' desireable due to cooling channel design. Also if you are thinking about cooling in injection molds versus part weight in general another interesting topic to look into is 'melt flipping' which will create a more balanced mold to be 'cooled' -

http://www.immnet.com/articles?article=406

Hope helps, good luck - Jim