Method of optimising the performance of refrigerant vaporizers including improved frost control method and apparatus

• US 5,233,841 A
• Filed: 06/28/1991
• Issued: 08/10/1993
• Est. Priority Date: 01/10/1990
• Status: Expired due to Term

• Current Assignee: KUBA Kaltetechnik GmbH
• Original Assignee: KUBA Kaltetechnik GmbH
• Inventors: Jyrek, Paul
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US07/723,494
• Time in Patent Office: 774 Days
• Field of Search: 62/223, 62/225, 62/211, 62/212
• US Class Current: 62/80
• CPC Class Codes: F25B 2700/11 Sensor to detect if defrost is necessary
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: F25B 2700/21175 of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25B 41/35 by rotary motors, e.g. by stepping motors
• CPC Class Codes: F25D 21/02 Detecting the presence of frost or condensate
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A method is described for the performance optimization of refrigeration devices fed with refrigerant, in particular of air refrigeration devices in which a setting value is formed for an electrically or electronically operatable expansion valve in dependence on different temperature measurements continually ensures the ideal filling of the vaporizer. The invention includes a method of optimising the performance of a fan air refrigerator and of determining the ideal timepoint for defrosting is described, with the time for defrosting being determined by a comparative monitoring of a temperature difference, on the one hand, and a time related monitoring of the refrigerant throughflow, on the other hand. In addition the cold room temperature is regulated by the supply air sensor by switching on and switching off the compressor.

Claims

1. A method of optimizing performance of a refrigeration device operated with a refrigerant and fed via an expansion valve, characterized in that:

in addition to a supply air temperature, both a vaporization temperature and an air cooler outlet temperature at an outlet tube are measured and a first temperature difference value measured between said supply air temperature and said vaporization temperature is determined;

said difference value is multiplied by a factor to provide a computed temperature value and said computed temperature value which is obtained is compared with a second temperature difference value measured between said air cooler outlet temperature at an outlet tube and said vaporization temperature to provide a comparison value; and

the expansion valve at an inlet side of the refrigerator device is controlled responsive to said comparison value in such a way that said air cooler outlet temperature provides said second temperature difference value at least substantially the same as said computed temperature value.

2. The optimizing method in accordance with claim 1, characterized in that said vaporization temperature is measured by means of a temperature sensor coupled to a vaporizer tube.

3. The optimizing method in accordance with claim 1, characterized in that said first and second temperature difference values, said computed value and said comparison value are continuously formed and said expansion valve is periodically controlled.

4. The optimizing method in accordance with claim 1, characterized in that the control of the expansion valve (EV) is always effected when said comparison value lies outside of a predetermined tolerance range.

5. The optimizing method in accordance with claim 1, characterized in that during a phase of commencing use of the refrigerator device a periodic control used for control of the expansion valve differs from a periodic control used in normal operation.

6. The optimizing method in accordance with claim 1, characterized in that the expansion valve is positionable and includes an adjustable valve needle.

7. The optimizing method in accordance with claim 1, characterized in that a processing of said measured values and a formation of control signals for the expansion valve takes place in a computing unit which is provided with a specially prepared program.

8. The optimizing method of claim 1 wherein said vaporization temperature and said cooler outlet temperature measuring step is performed continuously.

9. The optimizing method of claim 1 wherein said vaporization temperature and said cooler outlet temperature measuring step is performed periodically.

10. The optimizing method of claim 1 wherein said difference measuring step measures said difference in degrees Kelvin.

11. The optimizing method of claim 10 wherein said factor is between about 0.6 and 0.7.

12. The optimizing method of claim 11 wherein said factor is about 0.625.

13. The optimizing method of claim 1 wherein said temperature comparing step is performed continuously.

14. The optimizing method of claim 1 wherein said temperature comparing step is performed periodically.

15. The optimizing method of claim 2 wherein said temperature sensor is coupled to said vaporizer tube about in a region one-half a length of said vaporizer tube.

16. The optimizing method of claim 6 wherein said positionable expansion valve is electrically positionable.

17. The optimizing method of claim 16 wherein said electrically positionable expansion valve is digitally controllable.

18. A method of operating a refrigeration device, comprising the steps of:

determining a first difference temperature between an air supply temperature and a vaporization temperature;

multiplying said first difference temperature by a predetermined factor to provide a computed temperature;

determining a second difference temperature between an air cooler outlet temperature at an outlet tube and said vaporization temperature;

comparing said computed temperature with said second difference temperature; and

controlling an expansion valve of the refrigeration device to provide said second difference temperature at least about equal to said computed temperature.

19. The operating method of claim 18 wherein said difference determining step determines said difference between said air supply temperature and said vaporization temperature in degrees Kelvin and said predetermined factor is between about 0.6 and 0.7.

20. The operating method of claim 19 wherein said predetermined factor is about 0.625.

21. A refrigerator, comprising:

means for measuring a first temperature difference between and air inlet temperature of a refrigerator and a vaporization temperature of a refrigerant of said refrigerator;

means, coupled to said first temperature measuring means, for computing a temperature value from said first temperature difference by multiplying said first temperature difference by a predetermined factor;

means for measuring a second temperature difference between a vaporizer outlet temperature and said vaporization temperature; and

means, coupled to said second temperature difference measuring means and to said computing means, for controlling a temperature of said refrigerant such that said second temperature difference approximately equals said computed temperature difference.

22. Method of optimising the performance of refrigeration devices which are operated with a refrigerant and are fed via an expansion valve, in particular the performance of fan air refrigerators, in which, in addition to the air entry temperature or the supply air temperature (tL 1), both the vaporization temperature (t_O) and also the temperature at the air refrigerator outlet (t_Oh) are measured continuously or periodically and the difference value (δ

t_l) between the supply air temperature (tL

     1) and the vaporization temperature (t_O) is determined, in which this difference value (δ

t₁) is multiplied by a factor between 0.6 and 0.7, and the computed temperature value which is obtained is compared with the difference value (δ

t_oh) of the temperature at the air refrigerator outlet (t_oh), and the vaporization temperature (t_o), and in which the expansion valve (EV) at the inlet side of the air refrigerator is then controlled continuously or periodically in dependence on the result of the comparison in such a way that the temperature at the vaporizer outlet (t_Oh ) is at least substantially the same as the computed temperature value, characterized in that the difference value (δ

t₁) between the supply air temperature (tL

     1) and the vaporization temperature (t_O) is monitored for the purpose of determining the ideal defrosting time point of the refrigeration device with respect to exceeding a predeterminable boundary value;

in that, in the case of exceeding this boundary value, a compressor and fan are switched off and a defrosting heating device is switched in until the air refrigerator has reached a predeterminable temperature corresponding to the ice-free state; and

in that the compressor is then switched on again and also the fan with a time delay relative to the compressor.

23. Method in accordance with claim 22, characterized in that the switching on of the fan takes place when the vaporization temperature (t_O) has reached a predeterminable value.

24. Method in accordance with claim 22 characterized in that, in parallel to the monitoring of the difference temperature (δ

t₁), a monitoring of the refrigerant throughflow is effected with respect to a reduction of the throughflow which extends over a predeterminable time interval, and in that the switching on of the defrosting heating device takes place in dependence on both criteria.

25. Method in accordance with claim 22, characterized in that the switching on and switching off of the compressor is effected in dependence on the supply air temperature (tL 1) and a room thermostat function is thereby realised.

26. Apparatus for carrying the method in accordance with claim 22 comprising an air refrigerator (XL), an expansion valve (EV) arranged in the refrigerant supply line, temperature sensors for determining the supply air temperature (tL 1), the vaporization temperature (t_O) of the refrigerant and the overheating temperature (t_Oh) at the and of the air refrigerator, and also a computing unit for forming the setting values for the expansion valve, characterized in that a further temperature sensor is provided for the determination of the heating switch off temperature (T_STB) corresponding to an icefree state of the air refrigerator (KL) and is connected with the computing unit (KLR);

in that signal values corresponding to the degree of opening or to an angle of opening of the expansion value (EV) form evaluatable parameters for the refrigerant throughflow in the computing unit (KLR); and

in that the switching on and switching off of the air refrigerator (KL) and also of the fan are controlled via the computing unit (KLR).

27. Apparatus in accordance with claim 26, characterized in that a needle valve or ball valve controlled by a stepping motor is used as the expansion valve (EV);

and in that the respective degree of opening of the expansion valve (EV) can be detected in the computing unit (KLR) by step counting procedures.

28. Apparatus in accordance with claim 26, characterized in that the comparison time interval for the change of the refrigerant throughflow can be set in the computing unit (KLR).

29. Apparatus in accordance with claim 26 characterized in that, for the provision of a room thermostat function, the signal delivered from the sensor for the supply air temperature (tL 1) is compared in the computing unit (KLR) with a predeterminable desired value and a switching signal for the compressor control is generated in dependence on the exceeding or falling short of a tolerance range related to this desired value.

30. Apparatus in accordance with claim 29, characterized in that the tolerance range associated with the desired value is adjustable.

31. Method of claim 22 wherein said factor is about equal to 0.625.