think of it as a battery. it stores a large vacuum reserve while the engine is running. then its used whenever you use the device attached to it requiring the vacuum source. without it things like your heater and ac controls would not work properly because they require a large amount of vacuum to operate that your engine alone cannot supply fast enough.
why are vacuum flasks called vacuum flask
k Vacuum flask
Gold Flasks Mount Stones Elixirs Transmutes Extended time for flasks These are just a few of the many advantages
the flasks are stoppered to prevent evaporation of sample since the acetic acid is somewhat a volatile liquid
If only the silvering is gone, it can still be used, but it won't be as good. However, quite often the silvering is inside the vacuum compartment; if the silvering has vanished because the glass cracked, it is very probably unsafe to use. A thermal flask works by preventing heat conduction (the vacuum layer will not conduct heat) and by preventing heat radiation (the silver layer reflects the heat back at the contents). Without the silver layer, the heat will not be reflected. The flask will still work, but will lose or gain heat faster that it would if the silvering was intact. Note: The "silvering" on older flasks may be mercury. If the envelope is cracked and the mercury evaporates, it could prove toxic. Newer flasks use aluminum.
why are vacuum flasks called vacuum flask
Heat energy, like light energy, can be reflected by some materials. ~MVMMS
k Vacuum flask
The motivation is to avoid heat transfer by thermal radiation.
To insulate a non-vacuum flask, a non- heat conducting material such as Styrofoam is put between the layers.
This is from wikipedia:The vacuum flask was invented by Scottish physicist and chemist Sir James Dewar in 1892 and is sometimes referred to as a Dewar flask after its inventor. The first vacuum flasks for commercial use were made in 1904 when a German company, Thermos GmbH, was formed. Thermos, their trademark for their flasks, remains a registered trademark in some countries but was declared a genericized trademark in the U.S. in 1963 as it is colloquially synonymous with vacuum flasks in general.
by inhibiting heat conduction
The round bottoms on these types of flasks allow more uniform heating and/or boiling of liquid. Thus, round-bottom flasks are used in a variety of applications where the contents are heated or boiled. Round-bottom flasks are usually used in distillation by chemists as distilling flasks and receiving flasks for the distillate One-neck round-bottom flasks are used as the distilling flasks in rotary evaporators.This flask shape is also more resistant to fracturing under vacuum, as a sphere more evenly distributes stress across its surface.
Um......your question is worded oddly, but the way an thermos is insulated is by having a vacuum between it's two flasks. The vacuum causes heat transfer to reduce greatly.
Numerous stores sell vacuum flasks. One can purchase a vacuum flask at Walmart, Kmart, Sears, Home Depot, Lowe's, Target, Ace Hardware and many other places.
A real one is a vacuum flask (or better: two flasks with a vacuum between them) - and so the only heat loss is via radiation (except at the cap). But most today are simply foam insulation.
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