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Vacuum flasks are thermally insulated double wall vessels. The narrow space between the two walls is evacuated which dramatically reduces thermal transfer. The near absence of air molecules minimizes thermal transfer by convection. Reflective surfaces in the vacuum space minimize radiant thermal transfer and the separation between the inner and outer wall minimizes thermal transfer by conductance. In summary, a vacuum flask thermally decouples a flask's payload from the external environment. The most common application of vacuum flasks is the storage or transmission of cryogenic fluids such as liquid nitrogen or liquid natural gas which can be maintained at extremely very low temperatures for extended durations. National K Works specializes in designing and manufacturing vacuum flasks exclusively for thermally insulating instruments from hostile temperature environments.

Vacuum flasks provide very effective thermal insulation. The insulation is passive and the largest portion of thermal transfer into the vacuum flask occurs by conductance through the neck of the inner wall and by the electrical wiring or mechanical feed through entering the vacuum flask (thermal leakage). The small amount of conductance eventually raises the inner temperature within the vacuum flask which limits the payload's duration within hostile high temperature environments to a finite duration.

An additional form of heat gain in the vacuum flask is the heat generated by the electronics within the vacuum flask. Since the vacuum flask thermally decouples the contents of the flask from the external environment, the heat dissipated by the electronics can not escape from the vacuum flask and consequently increases the inner temperature within the vacuum flask which also limits the payload's duration within hostile high temperature environments.

The duration can be extended by increasing the specific heat (thermal mass) within the vacuum flask in the form of separate heat sink material or by increasing the payload assembly's total specific heat (changing materials and/or quantity of material). Typical application durations are 1 to 24 hours. The duration is a function of the ratio of heat gain (by thermal leakage plus heat dissipated from the electronics) to specific heat (thermal mass) within the vacuum flask. In other words, the duration can be extended by increasing the amount of specific heat within the flask. Unlimited durations can be achieved by actively cooling the flask and removing the small amount of thermal leakage into the flask plus the heat dissipated by the electronics.

Vacuum Flask Tea Coffee Glass Liner Thermos Japan Made 138 Brown 1.9Ltr

VOGMAX Outdoor hand-ground coffee maker, full set of utensils, filter cup, pour-over pot combination - black 

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Vacuum Flask Tea Coffee Glass Liner Thermos Japan Made 138 Brown 1.9Ltr

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