Refrigeration – Refrigeration producer – Sorbent type
Reexamination Certificate
2000-01-21
2001-09-04
Doerrler, William (Department: 3744)
Refrigeration
Refrigeration producer
Sorbent type
C062S494000
Reexamination Certificate
active
06282918
ABSTRACT:
The invention refers to an absorption refrigerating apparatus of steel, where a refrigerant by means of an absorption liquid, in which the refrigerant is dissolvable, circulates through in turn a boiler where refrigerant is liberated from the absorption liquid, a condenser where the refrigerant condenses, an evaporator where the refrigerant evaporates, an absorber where the refrigerant is absorbed by the absorption liquid, and an absorber vessel for collecting the absorption liquid, from which absorber vessel the absorption liquid circulates back to the boiler, where the absorption liquid is heated in a so-called pump pipe so that the refrigerant is again liberated from the absorption liquid.
Such a refrigerating apparatus is known through e.g. EP patent No. 366 633.
Absorption refrigerating apparatuses are usually made of soft carbon steel. The reason for this is that the cold working qualities and weldability are very good at the soft carbon steel. In order to avoid corrosion in the apparatus, where the absorption liquid is water and the refrigerant ammonia, a small amount of sodium chromate (Na
2
CrO
4
) is added to the water-ammonia solution. A thin film consisting of chrome and iron oxides (Cr
2
O
3
and Fe
2
O
4
)is built up on the surface of the steel tubes and protects the apparatus from corrosion. If a crack would appear in the protecting film, more chromate is immediately taken from the solution to repair the crack.
Such hexavalent chrome combinations are, however, poisonous for human beings and possibly cancerogenic, and it is therefore desirable to exclude these substances from the apparatus.
If on the other hand a corrosion inhibitor is missing in the apparatus magnetite is formed under development of hydrogen gas according to the following sum reaction:
3Fe+4H
2
O→Fe
3
O
4
+4H
2(g)
The reaction velocity at room temperature is very low, but becomes considerable at temperatures exceeding 100° C. This results in that the apparatus will cease to work within very short time owing to corrosion products which are deposited and obstruct the pump pipe, which has the narrowest cross section for the circulating liquid.
The object of the invention is to bring about an absorption refrigerating apparatus of the kind introductorily set forth, where the construction is such, that corrosion, and by that obstruction of the pump pipe is suppressed.
This object is reached by the apparatus according to the invention thereby that the pump pipe is made of a material, which is more corrosion resistant to the media in the apparatus than the steel material in at least the condenser, evaporator, absorber and absorber vessel, and that in the boiler there are no joints between different materials, which can cause galvanic corrosion.
REFERENCES:
patent: 4185470 (1980-01-01), Eber
patent: 4362029 (1982-12-01), Blomberg et al.
patent: 4914919 (1990-04-01), Walfridson et al.
patent: 5001904 (1991-03-01), Blomberg
Eriksson Staffan
Levin Per
Lindhagen Carl
Aktiebolaget Electrolux
Doerrler William
Jones Melvin
Pearne & Gordon LLP
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