Measurement Unit
1. Power: W, Kw 1Kw=3.412BTU/hr (British thermal units/hour)=1.36 (horsepower)=864Kcal/hr
2. Weight: kg: 1Kg=2.204621b (pound)
3. Flow velocity: m/min
4. Flow rate: m3/min, kg/h
5. Specific heat: Kcal/(kg℃): 1Kcal/(Kg℃)=1BTU/hr.°F=4186.8J/(Kg℃)
6. Power density: W/cm2: 1W/cm2=6.4516 W/in2
7. Pressure: Mpa
8. Thermal conductivity: W/(m℃): 1 W/(m℃)=0.01J/(cm s℃)=0.578Btu/(ft.h.F)
9. Temperature: ℃: 1F=9/5℃+32 1R=9/5℃+491.67 1K=1℃+273.15
Power Calculation
The calculation of heating power includes the following three aspects:
Power during operation
Power during startup
Heat loss in the system
All calculations should consider the worst-case scenario:
Lowest ambient temperature
Shortest operating cycle
Maximum operating temperature
Maximum weight of the heating medium (maximum flow rate for flowing medium)
Steps for calculating heater power:
Based on the process, draw a flow chart of the heating process (without involving material form or specifications).
Calculate the heat required for the process.
Calculate the heat and time required for system startup.
Redraw the heating process flow chart, consider an appropriate safety factor, and determine the total power of the heater.
Determine the sheath material and power density of the heating element.
Determine the form, size, and quantity of the heater.
Determine the power supply and control system of the heater.
