Method for detecting changes in a first flux of a heat or cold transport medium in a refrigeration system

• US 20050172647A1
• Filed: 04/12/2003
• Published: 08/11/2005
• Est. Priority Date: 04/22/2002
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Rasmussen, Bjarne Dindler, Thybo, Claus, Izadi-Zamanabad, Roozbeh
• Granted Patent: US 7,685,830 B2
• Time in Patent Office: Days
• US Class Current: 62/129
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2700/1352 at the inlet
• CPC Class Codes: F25B 2700/195 of the condenser
• CPC Class Codes: F25B 2700/197 of the evaporator
• CPC Class Codes: F25B 2700/21163 of the refrigerant at the outlet of the condenser
• CPC Class Codes: F25B 2700/21172 at the inlet
• CPC Class Codes: F25B 2700/21173 at the outlet
• CPC Class Codes: F25B 2700/21175 of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25D 2500/04 Calculation of parameters
• CPC Class Codes: F25D 29/008 Alarm devices

Abstract

The invention concerns a method for detecting changes in a first flow of a heating or cooling medium in a refrigeration system whereby the first flow is conveyed through a heat exchanger wherein occurs heat transfer from the first flow to a second flow of a heating or cooling medium. The earliest possible detection of the changes is desired. For this it is provided that for the supervision of the first media flow moving through the heat exchanger a change in the enthalpy of the second media stream or a value derived therefrom is determined.

Claims

1-12. -12. (canceled)

13. A method for detecting changes in a first media flow of a heat or coldness transport medium in a refrigeration system, the method comprising the steps of causing the first media flow to move through a heat exchanger in which a heat transfer between the first media flow and a second media flow of a heating or cooling agent occurs, and wherein for the control of the first media flow flowing through the heat exchanger by determining the change in the enthalpy of the second media flow or a value derived therefrom is determined.

14. The method according to claim 13, wherein for the determination of the change in the enthalpy of the second media flow a mass flow and a specific enthalpy differential of the second media flow across the heat exchanger are determined.

15. The method according to claim 14, wherein for the determination of the specific enthalpy change of the second media flow, at the input of an expansion valve the temperature and the pressure of the second media flow is determined and at the output of the heat exchanger the temperature of the second media flow and either the pressure at the output of the heat exchanger or the boiling temperature of the second media flow at the input of the heat exchanger are determined.

16. The method according to claim 13, wherein a specific enthalpy change of the first media flow across the heat exchanger is determined.

17. The method according to claim 13, wherein the second media flow from a pressure differential across and the opening degree of an expansion valve is determined.

18. The method according to claim 13, wherein the second media flow from operating data and a difference in the absolute pressure across a compressor together with the temperature of the second media flow at the compressor is determined.

19. The method according to claim 17, wherein the first media flow from the second media flow and a ratio of the specific enthalpy change of the second media flow and the specific enthalpy change of the first media flow across the heat exchanger are determined.

20. The method according to claim 17, wherein the first media flow is compared with a desired value.

21. The method according to claim 17, wherein a residual is formed as the difference between a first value, which is formed from a first pregiven mass flow of the first media flow and the specific enthalpy change, and a second value which corresponds to the change in the enthalpy of the second media flow, and that one monitors the residual.

22. The method according to claim 21, wherein for the pregiven mass flow of the first media flow one uses an average value over a predetermined time interval.

23. The method according to claim 21, wherein a fault indicator S_i is formed according to the following rule:

$S_i=\{\begin{array}{c}{S}_{i-1}+s_i,\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>S_{i-1}+s_i><br><br>0\\ 0,\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>S_{i-1}+s_i\le <br><br>0\end{array}<br><br><br><br>\mathrm{with}<br><br><br><br>s_i=k_1<br><br>\left(r_i-\frac{{\mathrm{\mu <br><br>}}_0+{\mathrm{\mu <br><br>}}_1}{2}\right)$

where

r_i;

residual

k_i;

proportionality constant

μ

₀;

first reliability value

μ

₁;

second reliability value.

24. The method according to claim 13, wherein determination of a predetermined change includes the introduction of a thawing process.