Process for setting, controlling and monitoring the level in a r

Details Process for setting, controlling and monitoring the level in a r Process for setting, controlling and monitoring the level in a r

1994-05-27

1996-03-05

Tanner, Harry B.

Refrigeration

Processes

Compressing, condensing and evaporating

62202, 62225, F25B 4104

Patent

active

054957206

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/EP92/02739, filed 27 Nov. 1992, and is based, in turn, upon German national application P 41 39 064.4 of 28 Nov. 1991, under the International Convention.


FIELD OF THE INVENTION

The invention relates to a process for setting, controlling and monitoring the level in a refrigerant evaporator in a closed circuit of a refrigerator and evaporating a mass flow of refrigerant to a substantially dry gas.


BACKGROUND OF THE INVENTION

In this process in a refrigerant line arranged downstream of the refrigerant evaporator a heatable measuring unit is inserted. The refrigerant flows around it. The measuring unit is heated to a temperature which is greater than that of the refrigerant. The impact of liquid drops of the refrigerant on the measuring unit and therewith the moisture content of the gas originating from the refrigerant evaporator is established by measuring the energy required to evaporate the liquid drops impacting the measuring unit.
Such processes are known from DE-OS 39 34 801 and DE-OS 40 06 040. During the implementation of the known process in connection with the refrigerators described in both cited references it has been found that an optimal setting, control and monitoring of the level in the refrigerant evaporator based on the measuring signals at the measuring unit cannot always be achieved during the operation of the refrigerator. This is due in part, to insufficient signal processing.


OBJECT OF THE INVENTION

It is an object of the invention to provided an improved process for the setting, controlling and monitoring of the level in a refrigerant evaporator so that with regard to those operational situations for which the respective refrigerating machine is intended, the refrigerant evaporator can be optimally set, controlled and monitored.


SUMMARY OF THE INVENTION

This object is attained by comparing the detected measuring signal to a basic signal, which is composed of a first partial signal coming from the electronic noise of a measuring and evaluating unit used for the implementation of the process and of a second partial signal from the flow of dry refrigerant passing the measuring unit. The difference between measuring signal and basic signal is found and compared with an adjustable limit or reference value established for that level of moisture content of the gas, above which the gas may be considered wet. In this way it can be insured that signal variations based on the electronic noise and the movements and changes of the flow will not cause new settings or changes in the operational conditions of the refrigerant evaporator. By setting the limit value or the reference value, which correspond to a minimal acceptable moisture content of the gas, but can also correspond to a completely dry gas it is possible to adjust the process to various refrigerants and to various refrigerators.
It is possible to use as a measured value the temperature of the measuring unit, which is then detected by means of a temperature sensor. In this process one measures directly the cooling of the measuring unit occurring at the impact and evaporation of the liquid drops on its outer surface as a result of the heat needed for the evaporation. In this case voltage, current and/or electric power are kept constant.
Instead it is possible to establish the energy required for maintaining a constant temperature of the measuring unit above the reference temperature, whereby then the energy needed for the evaporation of the liquid drops is supplied to the measuring unit by an energy supply source which must anyway be provided for the heating of the measuring unit.
In this case the voltage, the current intensity or even the electric power, which are furnished by the energy supply source used for heating the measuring unit, can serve as the actual measured value.
A particularly precise and significant reading of the measured value results when a predetermined time interval is subdivided to equal time periods, a measuring signal in

REFERENCES:
patent: 4571951 (1986-02-01), Szymaszek
patent: 4835980 (1989-06-01), Oyanagi et al.
patent: 5050393 (1991-09-01), Bryant

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