Cartridge heater power density
The watt density of the cartridge heater is defined as the number of watts consumed per square inch of heated housing surface. For a specific application, the power density of the heater determines the temperature of the internal resistance wire, which determines the temperature of the jacket. These factors are critical to the correct heating application and the expected life of the heater. Special structural features can promote excellent heat transfer, so that high-density cartridge heaters can operate at a higher power density while maintaining the lowest possible resistance wire temperature of any type of cartridge heater.
The heater power density (w/in2) is calculated using the following formula:
Watt density = heater power
Heating length × heater diameter × 3.14
The heated length is the total length of the heater minus the unheated (cold) part. The standard N-type high-density toner cartridge heater is 3/8" at the front end and 1/4" at the disc end is not heated. This means that a 6-inch long heater will have an effective heating length of 5-3/8 inches.
The unheated part varies with the type of heater terminal.
For liquid immersion heaters, the maximum power density depends on the type of liquid being heated. The more viscous or viscous the liquid, the lower the maximum watt density. Higher watt density may cause the liquid to carbonize and accumulate on the heater jacket, which will cause premature heater failure. It is recommended to use a heater with a power density lower than the recommended maximum power density to obtain the longest heater life. If the actual heater power density is close to the recommended maximum power density, the problem can be solved by the following methods:
Increase the number, diameter and length of heaters.
Reduce the total power; however, this may increase the heating time.
Get a tighter fit (see Figure 2-Confirm fit).
The high-density toner cartridge heater designed for the maximum recommended power density allows the smallest heater to be used to obtain the required power and has a good service life. Under all conditions being the same, using a heater with a lower power density usually provides the best service life.