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Calculating Heat Load in a Mold & GPM of Coolant

Shot Wt. 34 lbs.
Cycle Time 65 sec.
Resin Polypro
spec heat .87 Btu / (lb. F) See Chart
spec heat H2O 1.003 Btu / (lb/ F) @ 55 F
Ejected Part Temp. 120 F
Melt Temperature 440 F
Delta T 320 F
Temp. Rise in H2O 5 F (This is max allowable temp rise 2-3 F is suggested)
One Gallon H2O 8.33 lbs.
One Ton Chiller 12,000 Btu

Heat Load (Resin Thru put x Spec Heat (Resin) x Delta T = lbs. / Hr. of coolant required
(Spec. Heat (Coolant) x temp rise of coolant)

Lbs. / Hr. of coolant required =GPM of Coolant Required
(Coolant lbs. / gal. X 60 x Min / Hr)

3600 / 65 Sec. Cycle = 55.3 Shots per hr. x 34 lbs. Per Shot = 1,880 Lbs./ Hr.
1,880 Lbs. Hr. x .87 Btu x 320 F Delta T = 523,447 Btu / Hr.
523,477 Btu / (1.003 Spec Heat x 5 F ( Temp Rise )) = 104,382 Lbs. Of Coolant Per Hr.
104,382 Lbs. Hr. / (8.33 Lbs. Gallon x 60 Min. / Hr). = 208.84 Gallon Per Minute
523,477 Btu Hr. / 12,000 = 43.6 Tons of Chiller Capacity Required

Resin Spec. Heat
ABS 0.49
CAB 0.39
HIPS 0.501
LDPE 0.76
HDPE 0.87
PA 6, 6/6 0.731
PC 0.438
PET 0.502
POM 0.715
PP 0.64
GF PPS 0.497
PVC 0.383
SAN 0.471
Hello, I want ,can I use your help about plastic molding flow diagram details.
- - - -> by: Henrik Hacopian
Dear Sir,

We have an injection molding machine, using polyethylene Terephthalate ( PET). The machine injection unit have heaters ( for screw ) needs water temperature of 20 degree Celsius. Also the machine needs 20 deg. Celsius for Hydraulic oil cooling. The machine has hot runner needs water temperature of 7 Degree Celsius.
The data on name plate shows that
For injection unit - 176 A is the largest heat load
For hot runner - 94 A is the largest heat load
Also the machine has dryer needs cooling power of 34 kw.
I calculated the heat load in a mold using your equations. But I would like to know how to select chiller by considering the heat load for injection unit, hot runner and dryer. Also is there any consideration for atmospheric temperature?
- - - -> by: George

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