FRH

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FRH is an abbreviation for "flameless ration heater," a water-activated exothermic chemical heater included with Meals, Ready-to-Eat (MREs), used to heat the food. US military specifications for the heater require that it be capable of raising the temperature of an eight-ounce entree by 100°F in twelve minutes, and that it display no visible flame.

The exothermic chemical reaction works by the process of oxidation-reduction, which is much similar to the process of rusting metals. When iron metal rusts, it is oxidized by the oxygen present in the air. In the case of the flameless ration heater, the metal used is magnesium. Magnesium is chosen because it is readily oxidized, which is due to the fact that it only has two electrons in its valence shell. The magnesium metal is mixed together with a small amount of iron in a pouch. To activate the reaction, a small amount of water is added, and the boiling point of water is quickly reached as the reaction proceeds. The role of iron in the heater is most likely as a catalyst, since it is used in a small amount. In this case, the iron is initially oxidized, and then reduced back to its elemental form as the magnesium is oxidized and sends its two valence electrons to iron [1].

[edit] References

• HowStuffWorks article on MREs

[edit] See also

• Self-heating can

[edit] External links

• Flameless stoves from zenstoves.net - details chemical reaction