OK, so why is your display name Q?
Two reasons: First, a number of years ago, a few people at my place of work started calling me "Q". This began as sort of a joke—as do most nicknames—due to a presentation that was made at one of our company's sales meetings. We used a James Bond theme, and I played the character Q, the go-to guy at the home office who came up with all the solutions, usually in the form of gadgets. Since I played that part in our office, it stuck.
Second, Q is a symbol used in vacuum, known as throughput, or torr·cfm. It's use should be more widespread among us dirty vacuum guys than it is. It's a rule-of-thumb mnemonic that permits one to convert from mass-flow (lbs/hr), to scfm, or to acfm at one pressure to acfm at another pressure with one simple intermediate step. I teach this in our vacuum school. The symbol caught on.
Here's the rule-of thumb using Q:
Q = torr·cfm = torr x acfm* = Throughput
ex: Q = 150 torr x 50 acfm = 7500
Q ÷ 760 = scfm
Q ÷ 169 = lb/hr (air equivalent, mass flow)
ex: 7500/169 = 44.37 lb/hr
If you have the same load, but want to operate at a different pressure, say 210 torr, then:
Q ÷ new pressure = 7500/210 = 35.71 acfm. Therefore, you can use a smaller pump. Mass flow remains the same.
If you have the same load, but want to operate at a different pressure, say 210 torr, then:
Q ÷ new pressure = 7500/210 = 35.71 acfm. Therefore, you can use a smaller pump. Mass flow remains the same.
* ACFM at the operating pressure
This should be used only as a rule-of-thumb, since there are other factors (e.g., temperature, molecular weight) that must be considered.
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