Refrigeration – With indicator or tester – Condition sensing
Reexamination Certificate
1999-03-25
2001-01-30
Tanner, Harry B. (Department: 3744)
Refrigeration
With indicator or tester
Condition sensing
C062S158000
Reexamination Certificate
active
06178758
ABSTRACT:
The present invention pertains to a refrigerating system with a refrigerating circuit for cooling a cooling room and to such a refrigerating system in particular, with a control means for detecting a defect of the cooling circuit.
A cooling circuit of the above kind includes an evaporator arranged in a cooling room to be cooled and passed by a coolant which enters the evaporator in cooled form, absorbs heat there and subsequently leaves the evaporator in heated form. Outside of the cooling room a unit is provided for, which again cools down the coolant exiting the evaporator and anew supplies it to the evaporator. However, energy or power, respectively, has to be supplied to said unit to enable it to carry out this cooling function of the coolant. This energy or power, respectively, in case of a compression circuit can be supplied to the cooling circuit e.g. by means of a compressor or in case of an absorption circuit—by means of a heating means.
Defects occurring in these cooling circuits can be coolant losses due to leakages, defects at the unit of energy or power supply, respectively, to the cooling circuit and others.
However, under certain circumstances such defects can be detected with difficulty only: Due to fabrication spreads, in absorption cooling circuits the efficiency may very from apparatus to apparatus. As a consequence, a final temperature achieved by the refrigerating unit, in the cooling room can differ from apparatus to apparatus so that for sure a conclusion as to a defect can for sure not be drawn on basis of the final temperature in the cooling room alone.
Furthermore, the final temperature achievable in the cooling room also depends on the ambient temperature. In addition, the time required for essentially reaching the final temperature during cooling down of a unit depends on the charging condition of the cooling room, a heavily charged cooling room e.g. under certain circumstances requiring distinctly long time for reaching its final temperature. Thus, it may happen that at a given time the actually possible final temperature has not yet been reached and in case of exclusive detection of the cooling room temperature existence of a defect could be concluded erroneously. Further dependencies result from the installation situation of the refrigerating unit so that here e.g. ventilation and cooling of a heat exchanger can be influenced.
However, it nevertheless is desirable that a defect in the cooling circuit is detected as soon as possible in order to request repair of the defect or taking the apparatus out of service. In particular leakages occurring in case of cooling circuits operated with ammonia can cause interference, maybe annoyance caused by bad smell, for a user of the refrigerator, this being the reason why also in this case early detection of defects of the cooling circuit is of great importance.
Thus, it is an object of the present invention to make available a refrigerating system with a cooling circuit permitting detecting of defects of the cooling circuit.
For solving this object, a refrigerating system is proposed which includes:
a cooling circuit for cooling a cooling room, said cooling circuit comprising an evaporator arranged in said cooling room and being passed by a coolant and the power supplied to said cooling circuit being adjustable,
a control means for providing a performance value stating the power to be supplied, to said cooling circuit,
a temperature sensor for providing a temperature measurement value essentially stating the temperature of the coolant in the evaporator, to said control means,
a clock for providing a given first time interval and a second given time interval subsequent to said first time interval, to said control means,
said control means during said first time interval providing a performance value stating a first essentially constant power to be supplied and upon termination of said first time interval providing a second given performance value stating a second power to be supplied, being greater than said first power to be supplied, and
wherein said control means at the beginning of said second time interval detects a first temperature value and at the end of said second time interval detects a second temperature value and issues a defect signal when the absolute value of the difference between said first and said second temperature values is less than a given value of difference.
The invention is based on the idea of not carrying out detection of a defect of the cooling circuit in an essentially stationary condition of the refrigerating system but to cause a non-stationary condition of the cooling circuit, in which parameters of the cooling circuit are subject to a notable temporal variation. From these temporal changes then conclusion is drawn to a correct function or to a defect, respectively, of the cooling circuit. In accordance therewith in accordance with the present invention the power to be supplied to the cooling circuit is adjusted to a first performance value during a first time interval and upon expiry of said first time interval the power supplied to the refrigerator is changed into a second performance value being larger than said first performance value, during a second time interval. Due to the difference between said first and said second performance values the non-stationary condition of the cooling circuit is brought about.
In accordance with the present invention the temperature of the coolant in the evaporator is provided as parameter of the cooling circuit, whose detection in the non-stationary condition forms a sensible indicator for the presence of a defect. Correspondingly, the refrigerating system comprises a temperature sensor which essentially records the temperature of the coolant in the evaporator and provides a temperature measurement value essentially reflecting said temperature.
With entry into the non-stationary condition, a control means in the beginning of the second time interval detects a first temperature value of said temperature sensor and in the end of said second time interval it detects a second temperature value of said temperature sensor. Subsequently, the control means calculates the difference of said two temperature values. If the absolute value of said difference is larger than a given value of difference, the control means concludes that no defect is present since the cooling circuit reacted on the changed condition sufficiently quickly. If the absolute value, however, is less than the given value of difference, the defect means concludes presence of a defect as the cooling circuit did not react on the changed operating condition in sufficient way and issues a corresponding defect signal.
Preferably, said first performance value is chosen such that it states a power supplied of essentially zero. This means that during said first time interval the cooling circuit is not effective and the cooling room is not cooled further. This time thus can be used for defrosting the evaporator and/or the cooling room, respectively. Herein it is advantageous that the period of said first time interval is defined such that defrosting as complete as possible, of the evaporator and/or the cooling room, respectively, is reached.
To permit reproducibility as good as possible, of detection, said second performance value at least in the beginning of said second time interval states an essentially constant power to be supplied.
However, it also is possible to carry out regulation of the cooling circuit already during said second time interval such that a temperature detected by a cooling room temperature sensor, of the cooling room assumes a given desired value. This measurement is meaningful in particular, when the above-mentioned essentially constant power to be supplied during the entire second time interval would cause cooling down of the cooling room below the given desired temperature thereof.
A particularly preferable solution results when in the beginning of said second time interval an essentially constant power is supplied and in the end of said time interval the power
Electrolux Siegen GmbH
Pearne & Gordon LLP
Tanner Harry B.
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