Failure diagnosing system for absorption chillers

• US 5,623,426 A
• Filed: 02/22/1995
• Issued: 04/22/1997
• Est. Priority Date: 02/23/1994
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Kamada, Yasushi, Yasuda, Masashi, Furukawa, Masahiro, Ozawa, Yoshio, Mizukami, Kazuaki, Suzuki, Hiroyuki, Kurogi, Yasuharu
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): VO, HIEN XUAN
• Application Number:
  US08/392,332
• Time in Patent Office: 790 Days
• Field of Search: 364/557, 364/185, 364/186, 364/505, 364/551.01, 371/29.1, 340/346.79, 62/107, 62/108, 62/109, 62/101
• US Class Current: 702/99
• CPC Class Codes: F25B 49/043 Operating continuously
• CPC Class Codes: G05B 23/0235 based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold

Abstract

A failure diagnosing system for an absorption chiller including an evaporator, absorber, etc. comprises a plurality of sensors for measuring at least one representative temperatures of each of two fluids participating in heat exchange in a specified heat exchange unit, and an arithmetic unit for receiving measurement data from the sensors. The arithmetic unit comprises a circuit for calculating an actual temperature difference using a simple calculation equation defined by a linear expression, a circuit for calculating the amount of heat exchange by the absorber, and a circuit for calculating the degree of abnormality of the absorber by comparing the actual temperature difference with an ideal temperature difference for the same amount of heat exchange as the calculated amount.

Claims

1. A failure diagnosing system for an absorption chiller comprising a plurality of heat exchange units including a regenerator, condenser, evaporator and absorber, the failure diagnosing system comprising:

temperature measuring means for measuring at least one representative temperature of each of two fluids participating in heat exchange at a specified heat exchange unit,

temperature difference data calculating means for storing a temperature difference data calculating equation comprising a linear expression containing the representative temperatures of the two fluids as its factors and using the calculating equation to calculate actual temperature difference data from the measurement data obtained by the temperature measuring means,

heat exchange amount deriving means for deriving by measuring and calculation the amount of heat exchange by the specified heat exchange unit or other amount of heat exchange which varies with said amount of heat exchange,

storage means having stored therein ideal temperature difference data for normal operation as related to the amount of heat exchange, and

abnormality identifying means for preparing abnormality data indicating an abnormality of the specified heat exchange unit by comparing the actual temperature difference data obtained by the temperature difference calculating means with the ideal temperature difference data for the same amount of heat exchange as the amount of heat exchange obtained by the deriving means.

2. A failure diagnosing system as defined in claim 1 wherein the heat exchange amount deriving means calculates the amount of heat exchange by the absorber based on the temperature of cooling water at the inlet and outlet of the absorber and the flow rate of the cooling water.

3. A failure diagnosing system as defined in claim 1 wherein the heat exchange amount deriving means calculates the amount of heat exchange by the evaporator based on the temperature of cold water at the inlet and outlet of the evaporator and the flow rate of the cold water.

4. A failure diagnosing system as defined in claim 1 wherein the abnormality identifying means calculates an abnormality degree A defined by the mathematical expression

5. A failure diagnosing system as defined in claim 1 wherein means is provided for nullifying abnormality identification by the abnormality identifying means when an absorbent pump for recycling an absorbent through the generator and the absorber has come to a halt.

6. A failure diagnosing system as defined in claim 1 wherein the temperature difference data calculating means has means for calculating an offset of temperature difference data as to the specified heat exchange unit, and means for correcting the result of calculation of the temperature difference data based on the calculated offset, and the corrected temperature difference data is fed to the abnormality identifying means as the actual temperature difference data.

7. A failure diagnosing system for an absorption chiller which system comprises:

sensor means for measuring the temperature of a plurality of fluids participating in heat exchange in a condenser and an absorber,

an arithmetic circuit for calculating condenser abnormality degree data and absorber abnormality degree data representing the abnormality degree of the condenser and that of the absorber by calculating condenser temperature difference data and absorber temperature difference data representing the mean temperature differences of the fluids through the respective condenser and absorber based on measurement data obtained by the sensor means and comparing each of these items of data with a corresponding normal value,

absorber abnormality degree modifying means for modifying the calculated absorber abnormality degree data in accordance with the magnitude of the calculated condenser abnormality degree data, and

failure identifying means for identifying a failure of the absorber based on the modified absorber abnormality degree data.

8. A failure diagnosing system as defined in claim 7 wherein the temperature difference data is a logarithmic mean temperature difference, and the abnormality degree data is an abnormality degree A defined by the mathematical expression

9. A failure diagnosing system as defined in claim 7 wherein the arithmetic circuit comprises means for calculating an offset of the temperature difference data as to each of the condenser and the absorber, and means for correcting the result of calculation of the temperature difference data based on the calculated offset, and calculates the condenser abnormality degree data and the absorber abnormality degree data each based on the corrected temperature difference data.

10. A failure diagnosing system for an absorption chiller comprising:

sensor means for detecting the temperature of an absorbent flowing toward an absorber, the condensation temperature of a refrigerant in a condenser and the temperature of cooling water flowing through the absorber and the condenser,

storage means having stored therein temperature correction data in accordance with the difference between the saturated vapor temperature of the condenser and the refrigerant condensation temperature using the cooling water temperature as a variable,

temperature correcting means for retrieving the temperature correction data from the storage means in accordance with the cooling water temperature obtained from the sensor means and correcting the refrigerant condensation temperature obtained from the sensor means with the retrieved temperature correction data,

concentration estimating means for estimating the concentration of the absorbent based on the refrigerant condensation temperature corrected by the temperature correcting means and the absorbent temperature obtained from the sensor means, and

abnormality identifying means for detecting occurrence of an abnormality based on the estimated concentration obtained from the concentration estimating means.

11. A failure diagnosing system as defined in claim 10 wherein the abnormality identifying means comprises calculation means for deriving a normal value of absorbent concentration based on a refrigeration load and cooling water temperature, and prepares and outputs diagnosis data representing the degree of the abnormality in accordance with the magnitude of the difference between the estimated concentration and the normal value of concentration obtained from the calculation means.

12. A failure diagnosing system as defined in claim 10 wherein the abnormality identifying means comprises:

means for calculating abnormality degree data representing the degree of abnormality of the condenser by calculating temperature difference data representing the mean temperature difference between the refrigerant and the cooling water to be subjected to heat exchange in the condenser from temperature measurement data as to the refrigerant and the cooling water and comparing the temperature difference data with a corresponding normal value,

means for calculating the deviation of the estimated concentration obtained from the concentration estimating means from a corresponding normal value, and

means for modifying the calculated concentration deviation in accordance with the magnitude of the calculated condenser abnormality degree data,

and detects occurrence of the abnormality based on the modified concentration deviation.

13. A failure diagnosing system for an absorption chiller comprising:

sensor means for detecting a refrigeration load and the temperature of cooling water flowing through an absorber and a condenser,

concentration detecting means for detecting the concentration of an absorbent flowing toward the absorber by actual measurement or measurement including estimation,

storage means having stored therein concentration characteristics representing variations in the concentration of the absorbent during normal operation using the refrigeration load and the cooling water temperature as variables,

calculation means for deriving a normal value of concentration of the absorbent from the concentration characteristics in the storage means based on the refrigeration load and the cooling water temperature obtained from the sensor means, and

abnormality identifying means for comparing the concentration detected by the concentration detecting means with the normal value of concentration derived by the calculation means and detecting occurrence of an abnormality based on the result of comparison.

14. A failure diagnosing system as defined in claim 13 wherein the sensor means further detects the condensation temperature of a refrigerant in the condenser, and the concentration detecting means comprises:

storage means having stored therein temperature correction data in accordance with the difference between the saturated vapor temperature of the condenser and the refrigerant condensation temperature using the cooling water temperature as a variable,

temperature correcting means for retrieving the temperature correction data from the storage means in accordance with the cooling water temperature obtained from the sensor means and correcting the refrigerant condensation temperature with the retrieved temperature correction data, and

concentration estimating means for estimating the concentration of the absorbent based on the refrigerant condensation temperature corrected by the temperature correcting means and the absorbent temperature detected by the sensor means.

15. A failure diagnosing system as defined in claim 13 wherein the abnormality identifying means comprises:

means for calculating abnormality degree data representing the degree of abnormality of the condenser by calculating temperature difference data representing the mean temperature difference between a refrigerant and the cooling water to be subjected to heat exchange in the condenser from the temperature measurement data as to the refrigerant and the cooling water and comparing the temperature difference data with a corresponding normal value,

means for calculating the deviation of the detected concentration from the derived normal value of concentration, and

means for modifying the calculated concentration deviation in accordance with the magnitude of the calculated condenser abnormality degree data,

and detects occurrence of the abnormality based on the modified concentration deviation.

16. A failure diagnosing system for an absorption chiller characterized in that the system comprises:

measuring means for obtaining the temperature of a refrigerant recycled through an evaporator, the temperature of cold water at the inlet and outlet of the evaporator and the flow rate of the cold water by acutal measurement or measurement including estimation,

first calculation means for calculating a refrigeration load from values measured by the measuring means,

second calculation means for calculating the logarithmic mean temperature difference of the evaporator from the refrigeration load and the cold water inlet and outlet temperatures obtained by the measuring means,

third calculation means for calculating a normal value of logarithmic mean temperature difference of the evaporator based on the refrigeration load obtained by the first calculation means,

fourth calculation means for calculating the degree of abnormality of the evaporator by normalizing the logarithmic mean temperature difference obtained from the second calculation means with the normal value obtained from the third calculation means,

memory means for storing variations in the abnormality degree of the evaporator obtained by the fourth calculation means with time over a specified period in the past, and

diagnosing means for detecting a change of the tendency for the abnormality degree to vary with time to a different tendency at a certain time, from the abnormality degree history stored in the memory means to thereby recognize that the refrigerant was contaminated with the absorbent at said time.

17. A failure diagnosing system as defined in claim 16 wherein the second calculation means comprises means for calculating an offset of the logarithmic mean temperature difference of the evaporator, and means for correcting the result of calculation of the evaporator logarithmic mean temperature difference based on the calculated offset, and the fourth calculation means calculates the abnormality degree of the evaporator based on the corrected logarithmic mean temperature difference.