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Text version of the page
W A T L O W
Application Guide catalog - 7347 Application Guide
Reference Data
Step 2: Heating of Plastic During the Operating CycleExamples of Applications
From Equation 1, (Page16).Q Continued(0.4 Btu/lb
F)
(280F)3.412 Btu/Wh= 4.1 Whwhere:w= weight of plastic charge = 2 oz. = 0.125 lb C
B =(0.125 lbs)
p = specific heat of plastic = 0.4 Btu/lb
F ∆ T= temperature rise = 280 F
Reference Data Step 3: Heat Required to Melt or Vaporize Materials During Initial Heating Not required since plastic is not present during initial heat-up.Q
C = 0 Step 4: Heat Required to Melt or Vaporize Materials During the Operating Cycle Not required since the plastic does not change phase during the moldingoperation.Q
D = 0 Step 5: Determine Thermal System Heat Losses Energy is required to replace heat lost to conduction, convection and radiation: a. Conduction losses through the insulated surfaces From Equation 3A, (Page17).Q
A
∆ T
t
e L1 =K 3.412
L=(5.2 Btu
in./ft
2 F
hr)
(2.08
ft
2 )
(280F)
(1 hr)(3.412 Btu/Wh)
(0.5 in.)= 1775 Whwhere:K= the thermal conductivity of
1 ⁄
2 inch rigid insulation board= 5.2 Btu
inch/hr
ft
2 FA= The total insulated surface area=2
(10
15) in
2 = 2.08 ft
2 144 in
2 /1ft
2 ∆ T= the temperature differential between the heated platen and the outsideinsulation at ambient= 350F - 70F = 280FL= the insulation thickness = 0.5 incht
e = exposure time = 1 hour 159