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The Non-Stick Schtick
I just ran across an ad for a cartridge heater with a non-stick coating that "eases heater removal." They claim that the coating is bonded to the heater sheath and requires no additional release agents. The ad also claims that the coating helps ensure uniform heat transfer and inhibits corrosion.
The first thing that strikes me is the recognition of the problem of bore seizure. It is a major difficulty with the use of conventional or solid heaters. There are two companies, to my knowledge, that manufacture non-stick, coated heaters. I have seen one at industrial shows demonstrating that their heater will slide down a trough faster that a non-coated heater ... how that adds credibility to their claims, escapes me.
Other questions come to mind ... heaters get pretty hot ... there is no mention of the temperature limits of an applied coating in the ad. One manufacturer claims that their coating is good to 1200 degF and follows that right up with a statement that their heaters can carry higher watt densities. The two claims seem a bit at odds, given the higher watt densities will produce higher temps.
Thermal-dynamics tells me that the optimum heat transfer happens under conditions of Conduction ... metal-to-metal contact contact wins every time.The bilateral sheath expansion of the Watt-Flex® cartridge heater will double sheath-to-bore contact and affect superior heat transfer as compared with any conventional design. This will provide more responsive heat and longer life for the split sheath heater.
Friday Funnies
I was in the store and I saw this man and woman wrapped and bar coded.
I asked, "Are you two an item?"
So I was having dinner with Garry Kasporov and there was a checked tablecloth.
It took him two hours to pass me the salt.
I said to the Gym instructor "Can you teach me to do the splits?"
He said, "How flexible are you?"
I said "I can't make Tuesdays".
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