Chiller Tonnage Design Parameters for the Plastics Industry

Following are plastics guidelines used to size a chiller to its specific needs.  The tables show the normal process chiller guidelines for chillers and towers used primarily in the plastics industry.  Blow molding, injection molding and extrusion are the main plastics uses for needing a chiller system.  Also included are basic heat exchanger and mechanical uses guidelines for water chillers.

Chillers	Towers
* 2.4 to 3.0 GPM/ton @ 10F "delta T"	* 85 F Leaving water temperature
* 12,000 BTU / HR / TON	* 95F Entering Water Temperature
* 20F - 60F Standard Supply Range	* 78F Wet Bulb
* Tonnage rating @ 50F supply temperature	* 3 GPM / Ton
* 85F Water cooled condenser (entering)	* 15,000 BTU / HR / Ton
* 95F Air cooled condenser (entering)	* Consult Manufacturer for other conditions

 

Decrease nominal tonnage by approximately 2% per degree below 50F leaving water temperature.

Increase nominal tonnage by approximately 2% per degree above 50F leaving water temperature.

Elevation must be taken into account when an air cooled chiller is being used.   Rule of thumb:  Every 2000 ft of elevation above sea level will reduce the condenser effective cooling by 6%, 4000 ft 12%.   So in short you need to oversize the condenser to compensate for the loss of density in the higher elevation air.

Heat Load Sizes

Plastics Industry

Injection Molding	30# /HR of H.D. Polyethylene ....=(STANDARD) 1 Ton of cooling
	35# /HR of L.D. Polyethylene/ Polypropylene ..= 1 Ton of cooling
	40# /HR of Nylon.............................................. = 1 Ton of cooling
	50# /HR of Polystyrene or ABS....................... .= 1 Ton of cooling
	65# /HR of PVC or Polycarbonate................... = 1 Ton of cooling
	70# /HR of P.E.T............................................... = 1 Ton of cooling
Extrusion	50# /HR of Polyethylene or Polypropylene...... = 1 Ton of cooling
	75# /HR of Polystyrene.................................... = 1 Ton of cooling
	80# /HR of PVC................................................. = 1 ton of cooling
Blow Molding	40# /HR of Polyolefins ......................................= 1 Ton of cooling

Mechanical & Extrusion Equipment

Mechanical	Air compressor (No after cooler) ..............................=.16 Ton of cooling/ Hp
	Air compressor (With after cooler) ..........................= .20 Ton of cooling/ Hp
	Vacuum Pump......................................................... = .10 Ton of cooling/ Hp
	Hydraulic Cooling ........ .= .1 Ton /Hp or 1.0 Ton of cooling for every 10 Hp
	Hot Runner Mold ............................ = 1.0 Ton of cooling/ 10.5 KW of heat
	Water Pump in Circuit........................................ .... = .2 Ton of cooling/ Hp
	Feed Throat - 400 Ton up machine.... = 1.0 Ton (.5 Ton if below 400 Ton)
Extrusion	Gear box cooling .............................................= 1.0 Ton of cooling/ 100 Hp
	Feed Throat 3" Screw or less ... .= 1.0 Ton of cooling (above 3" = 2.0 Tons)
	Barrel or Screw Cooling .............= 1 Ton of cooling / inch of screw diameter

For metric conversion factors see the links here