Refrigeration – Automatic control – Refrigeration producer
Patent
1998-06-18
2000-06-27
Tanner, Harry B.
Refrigeration
Automatic control
Refrigeration producer
62202, 62225, F25B 4104
Patent
active
060792205
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national stage of PCT/DE97/00136 filed Jan. 24, 1997 and based, in turn, upon German national application 196 03 175.3 filed Jan. 30, 1996 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a process for monitoring, adjusting and controlling the filling level of a refrigerant evaporator operating in a closed cycle of a refrigerating machine and the refrigerant mass flow supplied to the refrigerant evaporator which evaporates the refrigerant to a substantially dry suction line gas and to a refrigerating machine for carrying out the process.
In refrigerating systems operating in a closed cycle, a throttle valve is generally provided between the condenser and the evaporator.
With a throttle valve opened too little, the evaporator is filled too little with refrigerant with the consequence of only a small cooling power (refrigerating capacity). With a throttle valve which is opened too wide the evaporator is flooded with the consequence that the flow of liquid in the suction line has detrimental fluctuations.
It is known that superheating of the gas phase in the suction line for evaporator filling can be used. This superheating is contravariant to the refrigerating capacity of the evaporator, i.e. the smaller the superheating, the greater the refrigerating capacity of the evaporator. However, it must be ensured that the flow of the refrigerant fluid does not have detrimental fluctuations.
The use of superheating has two serious drawbacks.
(a) The superheating is only usable in the steady state.
(b) The smallest yet permissible superheating varies from apparatus to apparatus and from operating state to operating state and there is no possibility of determining this value on line (continuously) in operation. Thus the superheating must not be made so small that the refrigerant mass flow in the suction line will have detrimental fluctuations and the suction line gas will be wet.
From EP 0 613 545 B1 it is known to provide in the suction line downstream from the refrigerant evaporator, a heatable measuring body which is flushed by the suction line gas from the refrigerant evaporator. The measurement body is heated to a temperature which exceeds that of the suction line gas. The impingement of liquid droplets of the refrigerant on the measuring body and thus the moisture content of the suction line gas originating from the refrigerant evaporator is detected in that the energy required for evaporation of the liquid droplets on the measuring body is measured or determined.
Based upon a reference limit value, which establishes the permissible moisture content of the suction line gas, the moisture content in the suction line gas is limited by an appropriate regulation or control. This control regulation process is not concerned with an optimal refrigerating capacity. It provides only a protection of the compressor against liquid impact.
OBJECTS OF THE INVENTION
The invention has as its object to develop a process for monitoring, adjusting and controlling the evaporator filling with the goal of achieving an optimum refrigerant mass flow. This process should be usable under all operating conditions and should be appropriate for all refrigerating apparatus. However, the mass flow of the liquid phase should never exceed the permitted limiting value.
SUMMARY OF THE INVENTION
These objects are attained in a method of monitoring, adjusting and controlling the degree of filling of the refrigerant evaporator which involves a measurement of the fluctuations of the flow of the refrigerant in the suction line and from these short time oscillations or fluctuations, obtaining a measure of fluctuation. This measure has been found to represent an assessment of the degree of the filling of the evaporator and can be compared to a setpoint value. Where the fluctuation measure is less than the setpoint, the supply of refrigerant of the evaporator is increased and where the fluctuation measurement exceeds the setpoint, the refrigerant fee
REFERENCES:
patent: 4586828 (1986-05-01), Winter et al.
patent: 5195331 (1993-03-01), Zimmern et al.
patent: 5495720 (1996-03-01), Buck
patent: 5502970 (1996-04-01), Rajendran
Dubno Herbert
Tanner Harry B.
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