How long does a thermos keep warm?

If you are a lover of outdoor trips, hunting, fishing, then a thermos is simply vital for you. But which thermos will keep heat better, does heat conservation depend on the material of the product? Which one is better to choose? Which is most effective for keeping tea, coffee, food hot?

Heat saving

Many consumers believe that thermoses with glass bulbs keep food and drinks hot for the longest time. But expert opinion is somewhat different: classic thermoses made of metal are no worse than products with a glass bulb.

Average duration of keeping food and drinks warm equal to 6 hours. But if the vessel does not open for a long time, different models can retain heat from 12 hours to a day.

What determines the heat saving time?

The main purpose of purchasing a thermos is to keep food or drinks hot.

You can consider several criteria that affect heat saving.

Volume of the vessel. The longer you need to keep warm, the larger the volume of the dishes should be. It will keep drinks and food hot longer. If its main purpose is to store food, then, on the contrary, the size of the container should correspond to the portion. Otherwise, air masses filling the free space will quickly cool the food.

• Filling the vessel. This factor also affects heat retention. The more filled the vessel, the more efficiently it retains heat.Important: liquid food will stay hot longer than solid food.
• Neck. To transport food, it is recommended to use a neck with a diameter of 25 to 60 mm. With a narrower opening in the thermos, heat loss occurs longer.
• Flask. Glass flasks are more hygienic, but they are less practical. It is better to purchase a vessel with a narrow neck.
• Material. There is no definite answer which material is better, but if metal weighs about the same as a plastic vessel (metal is too thin), then you can forget about heat conservation.
• The product combines two circuits: external (body) and internal (flask itself). Between them there is free space in which there is vacuum or air. Heat is retained longer if there is a vacuum between the two cavities.

Types of thermoses according to thermal efficiency

Thermos flasks can be divided into several types according to their thermal efficiency:

Type

• Classical (thermos with a narrowed neck, retains heat well, convenient for traveling conditions). Standard volume: 500 ml.
• Jug (a vessel with a handle and spout, volume about a liter, not intended for camping conditions, used at home). The jug is less convenient to use and has a bulky design.
• Thermal mug. The design of the mug is similar to a classic thermos, but is equipped with double walls, which reduces heat transfer. There is a lid. Retains heat less than a classic thermos. Volume about 500 ml.
• Flask. It has a narrowed neck, designed for warm or cold liquid.
  Food thermos. Used for storing warm food, wide neck. The volume starts from a liter. Doesn't hold temperature well, but can hold heat for up to several hours.

By volume:

• Up to 0.5l.
• From 0.5–1 l.
• From 1–1.5 l.
• Over 1.5l.

Opening a thermos

• Screw loosening. The fastening is sealed and tight, but wears out quickly.
• Valve. There is a valve in the neck to remove the contents. Keeps warm better.
• Cork. Looks like a bottle cap. It holds heat well, but is impractical in everyday life and wears out quickly.

Several factors influence heat conservation: the volume of the vessel, the material of the body and flask, the width of the neck, and fastening.

According to expert opinion, classic thermoses made of metal or with a glass bulb are the best way to maintain the temperature at the proper level. There must be a vacuum between the walls, and the volume of the vessel must be more than a liter. This thermos can be used not only at home, but also on the go.