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Dewar Flask

Dewar flask used in laboratory

1. What is Dewar flask?
    1.1 Working principle of Dewar flask
    1.2 Advantage of Dewar flask
    1.3 Application of Dewar flask
2. Structure of Dewar flask
3. Use of Dewar flask
    3.1 Dewar bottle storage
    3.2 Handling of Dewar flask
    3.3 Dewar vessel
4. How to buy Dewar flask?

What is Dewar flask?

Dewar flask, also known as a thermos flask, is a more ideal container and tool for storing liquid gases, cryogenic research, and crystal component protection. The modern Dewar bottle was invented by Sir James Dewar, a Scottish physicist and chemist.

Working principle of Dewar flask

Heat transfer (or heat transfer) is a physical phenomenon in physics that refers to the transfer of heat energy due to temperature differences. Heat is used in heat transfer to measure the change in the internal energy of an object. There are three basic forms of heat transfer: heat conduction, heat radiation, and heat convection. As long as there is a temperature difference within or between objects, heat energy must be transferred from high to low temperatures in one or more of these three ways.

Advantage of Dewar flask

a. Compared to compressed gas cylinders it is capable of holding large volumes of gas at relatively low pressures.

b. Provides an easy-to-operate source of cryogenic liquids. Due to the robustness and reliability of the Dewar cylinder, its long retention time, and its own gas supply system, it can continuously output normal temperature gases (oxygen, nitrogen, argon) with a flow rate of up to 10m3/h using its built-in vaporizer and a high constant gas output pressure of 1.2Mpa (medium pressure type) and 2.2Mpa (high-pressure type), fully meeting the gas requirements under normal circumstances.

Application of Dewar flask

If the user has a large gas flow, multiple Dewar flasks can be connected in parallel or with an external vaporizer to meet the gas supply requirements. By adding an external vaporizer, the large output flow of a single Dewar cylinder can reach 50m3/h.

Dewar bottles can provide diversified uses, such as direct gas supply at the work site, which is used in a form similar to compressed gas cylinders; small and simple pipeline centralized gas supply; low-temperature liquid use, etc.

Structure of Dewar flask

Dewar flask is a super vacuum insulated stainless steel pressure vessel designed for the storage, transport, and use of liquid oxygen, liquid nitrogen, liquid argon, or carbon dioxide for the reliable and economical transport and storage of cryogenic liquid gases as well as for the in-situ storage and supply of liquid gases in a wide range of applications.

The structure and components of the Dewar bottle are the outer cylinder, inner cylinder, vaporizer, liquid valve, safety valve, discharge valve, pressure gauge, booster valve, service valve, and liquid level gauge.
Outer cylinderThe role of the outer barrel body, in addition to protecting the inner barrel body, it also forms a vacuum sandwich with the inner barrel body to prevent the intrusion of heat outside the bottle, reducing the amount of natural vaporization of low-temperature liquid inside the bottle.
Inner cylinderReserve low-temperature liquid.
VaporizerBy heat exchange with the inner wall of the outer barrel, the liquid gas in the bottle is converted into gas.
Liquid valveControl the Dewar bottle for liquid filling or liquid discharge from the bottle.
Safety valveWhen the pressure of the container is greater than the maximum working pressure, the automatic pressure relief, its starting pressure is slightly greater than the maximum working pressure.
Discharge valveWhen the Dewar flask is filled with liquid, this valve is used to discharge the gas in the gas phase space of the bottle to reduce the pressure inside the bottle so that the liquid can be filled quickly and smoothly. Another function is that when the pressure inside the bottle exceeds the maximum working pressure in storage or other situations, this valve can be used to discharge the gas inside the bottle manually to reduce the pressure inside the bottle.
Pressure gaugeIt indicates the pressure of the inner cylinder of the bottle.
Booster valveWhen the booster valve is opened, the liquid inside the bottle will exchange heat with the outer cylinder wall through the booster coil and vaporize into gas, which will enter the gas phase space on the upper part of the inner cylinder wall, so that a certain driving pressure (internal pressure) can be established in the cylinder to drive the low-temperature liquid inside the bottle and make it flow.
Service valveIt is used to open the pipeline pathway between the liquid vaporization circuit of the Dewar bottle and the inlet end of the user's gas, and can also be used to control the flow rate of gas.
Liquid level gaugeThe level meter visually indicates the height of the liquid level in the vessel. The installation location should be easy for the operator to observe and service .

Use of Dewar flask


Dewar bottle storage

Dewar flask is vaporized by absorbing heat from the outside of the outer chamber, which means that the heat exchange between the inside and outside is relatively intense. At the same time, the self-evaporation of the liquid inside the Dewar vessel determines that if it is left unused for a long time, the pressure rise will cause the safety valve to jump, and the liquid consumption of the Dewar bottle will increase. Therefore, Dewar bottle is not suitable for long-term storage of cryogenic liquids. The sensitivity to heat also dictates that Dewar bottles should be stored at the lowest possible ambient temperature. Open storage, exposure to the sun, and storage near heat sources are all unsuitable.

The safety valve is released to eliminate unnecessary losses caused by self-evaporation, so Dewar flask should be guaranteed a certain amount of gas. It is recommended that Dewar bottles be put into circulation and used immediately upon arrival.

Handling of Dewar flask

Dewar flask holds low-temperature liquid inside. It consists of an inner and outer container with a high vacuum zone in the middle. Crushing, dropping, or tipping under any circumstances may affect the insulation performance of the Dewar bottle. Therefore, care must be taken when handling Dewar flask.

Because of the low-temperature liquefied gas involved, the storage, handling, and use of Dewar bottles differ greatly from that of seamless steel cylinders.

Dewar vessel

A. Preparation

a. Check the bottle for any serious damage.

b. Check the bottle for abnormal frosting.

c. It is strictly forbidden to touch the explosion-proof piece and its protective cover device.

d. It is strictly forbidden to touch the protective cover device at the vacuum joint.

e. Do not connect the wrong valve, especially pay attention not to connect the liquid phase and gas phase valves wrongly.

f. Maintain a certain amount of dosage, generally not less than 9 standard cubic meters per day.

g. Do not vaporize at high speed for a long time to prevent the temperature of the gas supply from dropping and leading to frosting of the outer bile.

B. Dewar flask gas procedure

The supply pressure and volume of the Dewar bottle can be adjusted in a certain range. The basic steps are as follows.

a. Install a suitable pressure-reducing valve on the connector of the gas valve for the Dewar bottle.

b. Connect a suitable gas line between the gas-using equipment and the pressure-reducing valve.

c. Open the booster valve; by observing the pressure gauge, the pressure can be increased to the setting of the economic regulator (medium pressure 140psig, high-pressure 315psig).

d. Open the gas valve, adjust the pressure-reducing valve to the proper gas pressure and start using gas.

e. Close the valves of all Dewar bottles when you are finished using gas.

C. Dewar flask liquid step

The rate of liquid supply using Dewar bottles is adjustable, depending on the gas phase pressure of the liner and the saturation temperature of the liquid. For safety reasons, it is recommended to reduce the bottle pressure as much as possible when using liquids. The basic procedure for liquid use is as follows.

a. The inlet and outlet valves of the Dewar bottle to which the line is connected.

b. Connect the ramming line to the container to be filled. If it is an open container, an anti-splash device must be installed at the end of the filling line.

c. Open the filling valve and emptying valve of the container being filled.

d. Open the inlet and outlet valves of the Dewar bottle and control the flow rate.

e. After filling, close the valve of the container being filled, close the inlet and outlet valves of the Dewar bottle, and open the venting valve on the filling line to empty the residual liquid and gas in the filling line.

f. Remove the filling line from the container being filled, or remove the open container.

D. After use of Dewar flask

Close all valves and transport to a cool place for storage.

How to buy Dewar flask?

ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector.
If you are interested in our Dewar flask or have any questions, please write an e-mail to, we will reply to you as soon as possible.

    AntiTeck Life Sciences Limited

    A1-519, XingGang GuoJi, Yingbin Road, Huadu, Guangzhou, China, 510810
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