Automatic temperature and humidity regulation – Thermostatic – Expanding fluid
Patent
1996-07-29
1998-07-14
Tapolcai, William E.
Automatic temperature and humidity regulation
Thermostatic
Expanding fluid
G05D 2312
Patent
active
057791422
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for achieving a specific temperature behaviour of adjusting elements of valves or thermostatic apparatus, which elements operate in dependence on temperature, and an adjusting element operating in dependence on temperature.
One class of temperature-dependent adjusting elements, as disclosed, for example, in U.S. Pat. No. 5,044,170, has a pressure chamber which is filled partially with fluid and partially with gas, the gas-filled part of the pressure chamber containing at least in part the gaseous phase of the liquid. If the temperature to which the pressure chamber is exposed then changes, the temperature of the liquid-gas filling also changes, and consequently the pressure in the pressure chamber. The change in pressure can be detected either by measuring techniques or can be used directly to operate an actuator, for instance, to displace a diaphragm. If the liquid comprises a pure substance, the temperature behaviour of the adjusting element can be predicted relatively easily, because with pure substances there is a simple correlation between pressure and temperature. This correlation can be represented in a pressure-temperature graph by a single line. The adjusting element in the form of a signal transducer between the temperature and the desired output signal, for example, a displacement movement or the actuation of an electrical switch, accordingly has exactly the same simple correlation, which can also be easily predicted in advance.
But many of these pure substances, which are used for a number of common applications, are toxic or at least greatly harmful to the environment. Provided that the adjusting elements are sound and operational, this gives no further cause for concern, but in the event of damage, considerable threats to health or the environment are therefore posed. Disposal of such adjusting elements also becomes especially difficult. By virtue of their filling, the adjusting elements are then frequently classed as special-grade waste.
The invention is based on the problem of achieving a desired temperature-dependent adjustment without using toxic or ecologically harmful substances.
This problem is solved by a method for adjusting the temperature behaviour of adjusting elements which operate in dependence on temperature of valves or thermostatic apparatus which have an actuating element acted on by pressure in a pressure chamber, in that a zeotropic mixture is produced from at least two substances, the mixture is introduced into the pressure chamber and the ratio of component substances is adjusted in dependence on the desired temperature behaviour.
One is therefore no longer restricted to the use of a pure substance, which, as stated, is in many cases toxic or ecologically harmful. It is now possible to use substances that are not harmful to the environment and are non-toxic. The desired temperature behaviour is then achieved firstly by using not just one, but several substances and, secondly, by setting the ratio of these component substances so that the desired temperature behaviour is achieved. In most cases the adjusting elements do not need to be changed mechanically at all. By suitable selection of the substances and by suitable setting of the ratio of these component substances, it is possible to simulate the desired temperature behaviour. It should be noted, however, that when using several substances as the filling, the relationship between the temperature and the pressure is generally no longer a simple theoretical one. For zeotropic mixtures, however, the pressure is a clear function of temperature, the ratio of components and the density of the substance. Normally, the boiling point line of multi-substance mixtures differs from the condensing point line. Between the two lines there exists a region in a pressure-temperature graph in which a part of the liquid has already gone over into the gaseous phase, but another part is still in the liquid phase. It is in this region that the resulting pressure-temperature line is found; this can be determi
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Pedersen J.o slashed.rgen Trelle
Rudebeck Viggo
Danfoss A/S
Tapolcai William E.
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