A Cooling Element provides cooling to a medium in an instrument or a device that is being used for measurement. camping refrigerator It is particularly used when the medium temperature would exceed the permissible temperature limit of a pressure measuring instrument and this in turn could cause errors in the measurements. Through air circulation and heat radiation at the cooling element, the medium temperature is lowered sufficiently so that the limits of the measuring instrument can be met and any possible errors are eliminated.
According to the invention, a cooling element is provided which comprises two layers of foil material and an intermediate layer of liquid-absorbing, vapour-releasing material, said two layers being fastened to one another by means of connections such that a compartment is formed between them and the welded connections. In addition, the welded connection is formed within the circumference of the compartment and the welded connections are in liquid communication with a buffer reservoir via at least one flow restriction.
The welded connection is formed within the circumference because this makes it stronger than if only the edges necessary for forming a compartment were welded together. It also prevents the intermediate layer of liquid-absorbing, vapour-releasing materials from being crumpled.
In this context, the foil materials are of a thermoplastic plastic with a high moisture-vapour transmittance and a low water resistance at a temperature of more than 3800 g/m2/24h according to the testing norm ASTM E96-BW and a maximum water column of at least 4700 mm according to the testing norm ISO 811. The welding tear resistance of the two layers of foil material is also determined accordingly.
A welded connection is therefore more mechanically reliable, leak-proof and ready for finishing treatment substantially immediately after the actual welding operation than a glued or stitched connection. Furthermore, it prevents stress concentrations that could arise if the connection between the two layers of foil material were to be made with glue or stitching instead of welding.
It is thus possible to obtain a high-quality, leak-proof and durable cooling element in a simple manner and at a reasonable cost. The welded connection can be rounded at their corners and ends, which helps to reduce the formation of tears upon deformation of the cooling element during the use thereof, for example when the cooling element is bent as in the normal use of a rucksack.
Additional welded connections can be provided between the two layers of foil material within the circumference of the compartment (5) and these may even be welded in any position as desired. The additional welded connections provide the strength of the overall assembly, as they prevent the intermediate layer from being folded or crumpled.
Moreover, the buffer reservoir is of a maximal volume essentially equal to the liquid volume of the liquid-absorbing, vapour-releasing material when it is saturated with liquid, which makes it possible to obtain precisely one filling of the wick without making the cooling element thicker than necessary for this purpose. This prevents water pockets from forming, which are otherwise often the case with similar constructive variants of the cooling element.