Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1993-02-19
1994-11-29
Hofsass, Jeffery A.
Communications: electrical
Condition responsive indicating system
Specific condition
340625, 62129, 73305, G08B 2100
Patent
active
053693957
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a differential float means and sensor incorporating same. The differential float means is particularly, although not exclusively, envisaged for use in detecting the entrainment of a gas in a liquid. The sensor means is particularly, although not exclusively, envisaged for use in detecting excess refrigerant vapour entrained in refrigerant liquid in a refrigeration system.
The present invention will hereinafter be described with particular reference to use in refrigeration systems although it is of general applicability. For example, the invention could be used to detect the entrainment of a fluid, having a given specific gravity, in another fluid having a different specific gravity.
DISCUSSION OF PRIOR ART
When there is a loss of refrigerant from a refrigeration system refrigerant vapour becomes entrained in refrigerant liquid in both low pressure and high pressure lines in the refrigeration system. This greatly reduces the efficiency and effectiveness in cooling of the refrigeration system.
It is known to provide refrigeration cooling systems with a sight glass S (see FIG. 1) in a high pressure liquid supply (hereinafter referred to as the high pressure line) line so that a technician may observe the occurrence of refrigerant vapour entrained in the refrigerant liquid immediately up stream from a refrigerant expansion device. A disadvantage of the use of a sight glass S is that the entrained vapour can only be detected when inspected. An amount of refrigerant must be lost before the entrained vapour can be observed by a technician inspecting the refrigerant through the sight glass S. Also, due to the time between inspections, considerable amounts of refrigerant may leak from the refrigerant system (thus causing vapour to be circulated with the refrigerant liquid) before the technician observes vapour bubbles in the refrigerant.
It is also known to install a liquid level detector in a storage reservoir R (see FIG. 1) of the refrigeration system to monitor the proper functioning of the system. The detector is set to trigger an alarm in the event that the liquid level falls below a predetermined level. The detector includes a float switch for detection of changes in liquid level about the predetermined level. The float switch is a conventional nature designed to operate under the relatively high pressure conditions existing in the storage reservoir R.
There are some difficulties in installing and operating conventional float switches in the high pressure line. This is because for conventional float switches to operate they must comprise elements which are capable of floating in the liquid, whose level they are to detect, and capable of withstanding relatively high pressures. Hence, the specific gravity of the float switch must be less than the specific gravity of the refrigerant liquid yet, at the same time, be strong enough so as not to collapse under the pressure of the surrounding fluid. To this end the floats generally have relatively thick walls which are capable of withstanding the pressures experienced in the high pressure line, such as, for example, about 2 MPa and are relatively large in diameter so as to float in the refrigerant liquid.
A disadvantage of such an arrangement is that further refrigerant must be added to the storage reservoir to enable proper functioning of the relatively large float switch. The cost of adding the extra refrigerant is significant and in the case of horizontally disposed storage reservoirs it is sometimes impractical. Another disadvantage is that such float switches cannot detect low levels of refrigerant liquid in the high pressure line and thus can not detect vapour entrained in the refrigerant liquid in the high pressure line.
Location of the float switch in the reservoir has the added disadvantage that false level sensing of the float switch can occur where the refrigerant liquid is spinning as in a whirlpool (which is not uncommon). In such a case, the float switch may not show the actual amount of refrig
REFERENCES:
patent: 3365899 (1968-01-01), Cuny et al.
patent: 4138879 (1979-02-01), Liebermann
patent: 4876888 (1989-10-01), Ricketts et al.
Patent Abstracts of Japan, P-979, p. 101, JP,A,1-242938 (Nisshin Steel Co Ltd) 27 Sep. 1989.
Derwent Abstract Accesion No. 20943A/11, class H03, SU,A, 556334 (Shorokhov) 23 May 1977.
Hofsass Jeffery A.
Refrigerant Monitoring Systems Pty. Ltd.
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