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The Document of Electric Heating Designing |
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1.Power：W、kW |
1kW=3.412BTU/hr=1.36(HP)=864kcal/hr |
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2.Weight：kg |
1kg = 2.20462lb |
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3.Velocity of flow：m/min |
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4.Flux：m3/min、kg/h |
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5.Conductivity：kcal/(kg ℃) |
1Kcal/(Kg℃)=1BTU/hr.°F=4186.8J/(Kg℃) |
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6.Power density：W/cm2 |
1W/cm2=6.4516 W/in2 |
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7.Pressure: MPa |
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8.Heating quotiety:W/(m ℃) |
1 W/(m℃)=0.01J/(cm s℃)=0.578Btu/(ft.h.F) |
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9.Temp.: ℃ |
1F=9/5℃＋32 1R=9/5℃＋491.67 1K=1℃＋273.15 |
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| Calculating the heater power |
| Following three points are concered to calculate the heating power ： |
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Power for working |
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Power for Opening |
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System heat losing |
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| All the calculate should be under the worst condition: |
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The lowest environment |
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The shortest working period |
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Max operating Temp. |
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Max weight for heating medium(flowing medium is the max flowing) |
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| The step of designing the heater system： |
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According to the craftwork process, draw the technical flowing chart of the
heater. (It doesn't contain material and specification) |
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Calculating the needed energy for the craftwork |
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Calculating the needed energy and time while the system opening |
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Re-draw technical flow chart, and consider the right safety factor, and confirm
the total power for the heater. |
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Confirming the jacket material for the hating component and power density. |
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Confirming the size and amount for the heater |
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Confirming the electric resource and control system for the heater |
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| The calculate for heating power under the ideal condition： |
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The calculate for heating power under the ideal condition： |
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Power for system working |
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| Dispelling quantity of heat for heating system |
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Tube |
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Plane |
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| Meaning of symbol for ceremony： |
| P |
Power: kW |
Q |
Dispelling quantity of heat : Tube W/m；Plane W/m2 |
| m1 |
Medium Weight: kg |
λ |
Heating quotiety for warm-keeping material: W/mk |
| c1 |
Medium specific heat: kcal/kg℃ |
δ |
Thickness for warm-keeping material: mm |
| m2 |
Container weight: kg |
d |
Tube outer Dia.: mm |
| c2 |
Vessel specific heat：kcal/kg℃ |
L |
Tube Length: m |
| m3 |
Adding the weight and flow for medium per hour: kg/h |
S |
Area for dispelling quantity of heat: m2 |
| c3 |
Medium specific heat: kcal/kg℃ |
△T |
Temp. changes for the medium and environment : ℃ |
| h |
Heating hours: h |
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