Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Typical vacuum/pressure in a domestic vacuum/Thermos flask

Status
Not open for further replies.
Mr-Pooman

Mr-Pooman

Mechanical
Feb 7, 2022
8
I am trying to replicate a vacuum flask (on a low budget) with a 1m long 8 inch UPVC pipe forming the outer shell. A search of the internet suggests that the influence of convection stops around 10 Pa, however the vacuum pump I have, a two stage rotary 3 cfm advertised to achieve a vacuum of 2 PA, can only achieve around 350 Pa. My question is, what is the typical vacuum/pressure in a domestic vacuum/Thermos flask and how is it achieved? i.e. a vacuum pump or creating a void in the manufacturing process.
 
Replies continue below

Recommended for you

Sort by date Sort by votes
When we made them in the lab we always used 10E-5 Torr (1mPa) as an upper limit.
For large bulk storage tanks the limit is not as low, I recall using 0.05mbar (5Pa, ~40mTorr).
There also contain multilayer aluminized mylar foil in the vacuum space to reduce heat transfer.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
 
Upvote 0 Downvote
Thanks LittleInch and EdStainless, I'll just have to find a better pump. One thing EdStainless what volume do you consider to be bulk storage and why do you think this to be the case.
 
Upvote 0 Downvote
Thousands of liters is bulk storage, you know tanks that are 20' tall and larger.
It is twofold, there are limits on what is practical with that size installed outdoors, and they make up much of the difference with the layered aluminized mylar film.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Diulf
  • Locked
  • Question
Pressure in closed condensate tank
Replies
5
Views
782
EdStainless
EdStainless
Samingme755
  • Question
Pressure drop for heat exchangers 2
Replies
5
Views
3K
MJCronin
MJCronin
J
  • Question
Confined Flame in a Cylindrical Furnace for Glass Melting
Replies
2
Views
4K
EdStainless
EdStainless
Rubbman
  • Locked
  • Question
Vacuum pump - cooling plugging issue
Replies
1
Views
209
EdStainless
EdStainless
A
  • Locked
  • Question
Enthalpy related dillema in a steam piston engine
Replies
5
Views
4K
AndreiM
A

Part and Inventory Search

Sponsor

Back
Top Bottom