How do vacuum flasks keep hot liquids hot and cold ones cold? – Cheeki

We’ve got 99 problems and maintaining the temperature of liquids is one of them. Thank James Dewar (inventor of vacuum flasks) that we have a way of keeping our liquids at a desired temperature using vacuum flasks. You can think of a vacuum flask as a water bottle holding another bottle inside it but is separated by va.
You can think of a vacuum flask as a water bottle holding another bottle inside it but is separated by vacuum, with a supporting stand at the bottom. This basic structure provides thermal insulation or reduction of heat transfer. 

How Do Insulated Water Bottles Work – Buzio Bottle

Cheeki Classic Insulated Bottle Pink 600ml 1EA

Thermosteel 24 Hours Hot and Cold Flip Lid Cover Double Wall

How do thermos flasks keep drinks hot? - Quora

IMMEKEY 44 OZ（1.3L）vacuum thermos Double walled vacuum design ensures 48 hours of hot ，Green., Compared with the traditional stainless steel thermos

IMMEKEY 44 OZ（1.3L）Vacuum Thermos with Celsius Temperature Display Lid, 48 Hour Heat Retention,Green

Thermos 16 oz. FUNtainer Bottle

Best Insulated Water Bottle? Yeti vs Hydro Flask vs 12 Other

Thermos Stainless King 24-oz. Direct Drink Vacuum Insulated Bottle

My thermos flask worked fine for a few months until it suddenly

IMMEKEY 44 OZ（1.3L）Vacuum Thermos with Celsius Temperature

Can a thermos keep things cold? - Quora

Stainless Steel Water Bottle Double Wall Vacuum Insulated Sports

Bottle Stainless Steel OKADI Wide Mouth Thermos Vacuum Flasks