JPH06249533A - Failure diagnosis system for absorption type refrigerating machine - Google Patents

Abstract

PURPOSE:To provide a diagnosis system for accurately detecting a drop in heat exchange rate of a condenser in an absorption type refrigerating machine to allow the diagnosing of the cause of a failure based on the results. CONSTITUTION:A circuit section 71 of an arithmetic processing circuit 7 calculates a logarithmic average temperature difference of a condenser based on an actual measurement data obtained from a group of sensors 6. A circuit section 72 estimates a flow rate of a cooling water from an inlet temperature of a cooling water or the like based on a corresponding relationship between a heat exchange value at an evaporator and a heat exchange value at an absorber and a circuit section 73 calculates a heat exchange value at the condenser based on the flow rate of the cooling water estimated. Moreover, a circuit section 74 calculates a logarithmic average temperature difference in the normal operation based on a table indicating a relationship between the heat exchange value and the logarithmic average temperature difference in the normal operation as prepared previously. Then, a circuit section 75 calculates[j abnormality based on the logarithmic average temperature difference during the diagnosis of a failure and that in the normal operation sends the results to an output device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption refrigerator, and more particularly to a system for detecting a decrease in heat exchange rate of a condenser constituting a refrigeration cycle and diagnosing a failure of the refrigerator based on the detection. is there.

[0002]

2. Description of the Related Art In an absorption chiller, a condenser, an evaporator, an absorber, a regenerator and the like are connected to each other by piping to form one refrigeration cycle. In particular, double-effect absorption chillers are widely used because of their high refrigeration efficiency (see, for example, JP-A-62-77567 [F25B15 / 00]).

By the way, in the absorption refrigerator, the cooling water circulates between it and the outdoor cooling tower, so that the cooling water absorbs dust and the like in the outside air in the process. When such cooling water passes through a heat exchange unit such as an absorber or a condenser, the heat transfer surface becomes dirty and the heat exchange rate decreases.

Further, when a failure such as a vacuum abnormality occurs, the leaked gas collects on the lower body. Most of the gas is discharged to the storage chamber by the mechanism for discharging the gas from the lower body to the storage chamber, but as the pressure in the storage chamber increases, more gas remains in the lower body. In the lower body, since steam flows from the heat transfer tube of the evaporator to the heat transfer tube of the absorber, the non-condensable gas is collected around the heat transfer tube of the absorber and absorbs the water vapor in the absorber. Hinder. As a result, the logarithmic mean temperature difference of the absorber rises abnormally. In this way, when a certain kind of failure occurs, the logarithmic average temperature difference is reduced in one or a plurality of heat exchange units related to the cause of the failure, even though their heat transfer performance is not abnormal. Rises abnormally.

Therefore, conventionally, various sensors for measuring temperature, flow rate, concentration and the like are provided at the input / output portions of each unit such as a condenser and an absorber, and the sensor output is monitored to detect the heat transfer surface. Faults such as dirt and vacuum abnormality are detected.

In a general heat exchanger, the heat exchange amount Q
Is represented by the product of the heat exchange rate K and the logarithmic average temperature difference ΔT, and the heat exchange rate K, that is, the value K obtained by dividing the heat exchange amount Q by the logarithmic average temperature difference ΔT, is monitored. A drop is detected. This method is applied to other heat exchange units such as absorbers and condensers, and the cause of failure such as vacuum abnormality is diagnosed by knowing the type and combination of heat exchange units whose heat exchange rate is decreasing. You can

[0007]

However, in the absorption refrigerator, for example, in order to calculate the heat exchange amount of the condenser, a plurality of temperatures are measured in order to measure the temperatures and flow rates of the two media flowing in the condenser. Not only does it require a large space to install a meter, especially for a flow meter,
There is a problem that the cost increases.

The object of the present invention is to accurately estimate the decrease in the heat exchange rate by estimating the cooling water flow rate based on the heat exchange amount in the absorber without directly measuring the cooling water flow rate flowing through the condenser. It is to provide a failure diagnosis system capable of detecting the above.

[0009]

A failure diagnosis system for an absorption refrigerator according to the present invention is a first data processing for deriving temperature difference data according to a temperature difference between two media flowing into a condenser (11). Means, storage means for storing the correspondence between the temperature difference data of the absorption chiller during normal operation and the heat exchange amount in the condenser (11), and the flow rate Vc of cold water flowing into the evaporator (21), Cold water inlet temperature Tc_in, cold water outlet temperature Tc_o
ut, the temperature (cooling water intermediate temperature) Tco_mid of the cooling water flowing from the absorber (22) to the condenser (11), and the inlet temperature Tco_in of the cooling water flowing into the absorber (22), Second data processing means for estimating the cooling water flow rate Vco, the estimated cooling water amount Vco, and a condenser (11)
Based on the correspondence between the storage means and the third data processing means for calculating the heat exchange amount in the condenser (11) based on the measured data of the outlet temperature Tco_out of the cooling water flowing out from the tank and the intermediate temperature Tco_mid of the cooling water. A fourth data processing means for deriving temperature difference data in a normal state corresponding to the calculated heat exchange amount, temperature difference data in the normal state, and a temperature difference in a failure diagnosis obtained from the first data processing means. It is provided with fifth data processing means for judging the degree of abnormality of the condenser (11) by comparison with the data, and output means for outputting the judgment result of the fifth data processing means.

[0010]

When constructing the fault diagnosis system of the present invention,
In advance, in the normal state of the absorption chiller, the correspondence relationship between the heat exchange amount in the condenser and the temperature difference data (logarithmic average temperature difference) is tabulated or made into a function and stored in the first storage means.

In the failure diagnosis, the temperature difference data (logarithmic mean temperature difference ΔT) of the condenser (11) is measured and the evaporator is also used.
Flow rate Vc of cold water flowing into (21), cold water inlet temperature Tc_i
n, cold water outlet temperature Tc_out, absorber (22) to condenser
Temperature of cooling water flowing to (11) (cooling water intermediate temperature) Tco_
Mid temperature and the inlet temperature T of the cooling water flowing into the absorber (22)
Measure co_in.

In an absorption refrigerator, it has been empirically found that there is a certain relation expressed by, for example, a linear expression between the heat exchange amount in the evaporator (21) and the heat exchange amount in the absorber (22). Known to. Since the heat exchange amount is represented by the product of the medium flow rate and the inlet / outlet temperature difference, the cold water flow rate Vc, the cold water inlet temperature Tc_in, the cold water outlet temperature Tc_out, the cooling water intermediate temperature Tco_mid, and the cooling water inlet temperature Tco.
Once the measured data of _in is obtained, the flow rate of the cooling water passing through the absorber (22) and thus the condenser (11) can be estimated by using the above relationship.

Therefore, in the present invention, the heat exchange amount is calculated using this estimated cooling water flow rate. And
The normal temperature difference data corresponding to the calculated heat exchange amount is derived from the correspondence relationship stored in advance. By comparing the temperature difference data at the time of normal and the temperature difference data at the time of failure diagnosis, it is possible to accurately determine the degree of decrease in the heat exchange rate under the same heat exchange amount in the condenser (11), that is, the degree of abnormality. This enables failure diagnosis.

At this time, if the moving average processing for a predetermined time is performed on the estimated data of the cooling water flow rate Vco, the fluctuation (noise) due to the variation of the temperature measurement data is smoothed, and thereby more accurate. Fault diagnosis is possible.

[0015]

According to the failure diagnosis system of the absorption refrigerator according to the present invention, it is possible to accurately detect the decrease in the heat exchange rate based on the cooling water flow rate estimated by a proper method. It is not necessary to install a flow meter to directly measure the cooling water flow rate.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to a double-effect absorption refrigerator is described below in detail with reference to the drawings. As shown in FIG. 1, the absorption refrigerator uses water as a refrigerant and lithium bromide (LiBr) solution as an absorption liquid, and a condenser (11)
And an upper body (1) including a low temperature regenerator (12), a lower body (2) including an evaporator (21) and an absorber (22), a high temperature regenerator (3) including a burner (31), and high temperature heat The exchanger (4), the low temperature heat exchanger (5) and the like are connected to each other by piping. In addition, necessary sensors (not shown) are installed in the medium input / output unit of these multiple devices.
Is attached, and various physical quantities described later are measured.

Cooling water having a low temperature supplied from a cooling tower (not shown) first passes through the absorber (22) and then
The cooling water, which has passed through the condenser (11) and the temperature of which has risen, is returned to the cooling tower again. Further, cold water having a high temperature from the indoor unit (not shown) passes through the evaporator (21), and cold water having a low temperature cooled by this is supplied to the indoor unit.

FIG. 2 shows the configuration of a failure diagnosis system for the condenser (11). The sensor group (6) includes a pressure in the upper body (1) shown in FIG. 1, a refrigerant outlet temperature of the condenser (11), an outlet temperature Tco_out of cooling water flowing out from the condenser (11),
Cooling water intermediate temperature Tco_m between the absorber (22) and the condenser (11)
id, inlet temperature Tco of cooling water supplied to the absorber (22)
_In, a chilled water outlet temperature Tc_out of the evaporator (21), a chilled water inlet temperature Tc_in, and a cold water flow rate Vc, respectively.

The arithmetic processing circuit (7) shown in FIG. 2 is composed of a microcomputer, and has the following nine calculation sections (71) to (75).
It is equipped with The condenser logarithmic average temperature difference calculation unit (71) calculates the logarithmic average temperature difference of the condenser from the upper shell pressure, the refrigerant outlet temperature, the cooling water outlet temperature, and the cooling water intermediate temperature.

Specifically, the logarithmic average temperature difference ΔT of the condenser
(cond) is calculated by the following equation 1.

[0021]

[Formula 1] ΔT (cond) = (Tcond-Tco_out-Tcond + Tco_mid) / ln {(Tcond-Tco_out) / (Tcond-Tco_mid)}

Here, Tcond is the saturated vapor temperature in the condenser, and is calculated from the pressure in the upper body (1).

Cooling water quantity estimating unit (72) of the arithmetic processing circuit (7)
Is the cooling water intermediate temperature Tco_mid, the cooling water inlet temperature T
Based on the measurement data of co_in, cold water outlet temperature Tc_out, cold water inlet temperature Tc_in, and cold water flow rate Vc,
The estimated value Vco of the cooling water flow rate is calculated by the following equation 2.

[0024]

## EQU00002 ## Vco = Kv.Vc. (Tc_in-Tc_out) / (Tco_mid-Tco_in) + Cv

Here, Kv and Cv are values obtained experimentally, and in the general absorption refrigerator shown in FIG. 1, for example, Kv = 1.277 and Cv = −0.183 are set. To be done.

The condenser heat exchange amount calculation unit (73) in FIG. 2 has a cooling water outlet temperature Tco_out and a cooling water intermediate temperature Tco_m.
Based on id and the estimated cooling water flow rate Vco, the heat exchange amount Q of the condenser (11) is calculated by the following mathematical expression 3.

[0027]

## EQU00003 ## Q = Vco.multidot. (Tco_out-Tco_mid)

In the arithmetic processing circuit (7), the logarithmic average temperature difference calculating section (73) of the condenser in the normal state has a table of the correspondence relationship between the logarithmic average temperature difference and the heat exchange amount in the normal state. .

FIG. 5 is a qualitative graph showing the relationship between the heat exchange amount Q and the logarithmic mean temperature difference ΔT in the condenser. The solid line shows the relationship between the logarithmic mean temperature difference calculation in the normal state. Corresponds to the table stored in the department.
This relationship is created in advance by actually measuring the heat exchange amount of the condenser and the logarithmic average temperature difference under normal operating conditions.

The logarithmic mean temperature difference calculation unit (7
4) searches the table based on the heat exchange amount obtained from the condenser heat exchange amount calculation unit (73) in FIG. 1 and derives the logarithmic average temperature difference corresponding to the heat exchange amount.

The condenser abnormality degree calculation unit (75) calculates the abnormality degree from the logarithmic average temperature difference at the time of failure diagnosis and at the time of normality. Here, the abnormality degree A is obtained by normalizing the logarithmic mean temperature difference ΔT (Q) at the time of failure diagnosis by the logarithmic mean temperature difference ΔTs (Q) at the time of failure diagnosis in the graph shown in FIG. Is defined by

[0032]

## EQU4 ## A = {ΔT (Q) -ΔTs (Q)} / ΔTs (Q)

The output device (8) shown in FIG. 2 is used as a numerical data for the degree of abnormality of the condenser obtained from the condenser abnormality degree calculation unit (75) or as an alarm when the reference value is exceeded. Output to. As a result, it is possible to know that the performance of the condenser itself has deteriorated or a failure has occurred in another unit.

The graph of FIG. 4 is a comparison of the changes over time of the actually measured cooling water flow rate and the estimated cooling water flow rate calculated by the above-mentioned equation 2 in the process in which the refrigeration load fluctuates with time. is there. According to this, although there is some variation in the estimated cooling water flow rate, it is almost in agreement with the measured cooling water flow rate, and the validity of the estimation is proved. Therefore, the abnormality degree calculated as described above based on the estimated cooling water amount is
It has sufficient accuracy, and accurate failure diagnosis can be performed by monitoring this degree of abnormality.

By the way, in the above embodiment, since the heat exchange amount is calculated using the instantaneous value of the estimated value Vco of the cooling water flow rate, the estimated cooling water flow rate varies in the temperature measurement data as shown in FIG. As a result, time fluctuations occur. Therefore, in order to perform the abnormality determination of the condenser more accurately, it is necessary to monitor the abnormality degree for a certain period of time.

Therefore, as shown in FIG. 3, a constant time T is applied to the estimated cooling water amount obtained from the cooling water flow rate estimating unit (72).
Moving average processing unit for performing moving average over 10 minutes, for example
(78) is provided, and at the input side of the condenser heat exchange amount calculation unit (73), the cooling water outlet temperature Tco_out, the cooling water intermediate temperature Tco_mid, and the cooling water inlet temperature Tco_in are respectively T / 2 hours (for example, A FIFO (77) for performing a delay process of 5 minutes) is provided. Then, the moving average processing unit (7
8) and based on the data output from the FIFO (77),
Calculate the heat exchange rate of the condenser. On the other hand, the logarithmic average temperature difference of the condenser obtained from the logarithmic average temperature difference calculation unit (71) is also provided with a FIFO (76) for performing a delay process of T / 2 hours, and is output from the FIFO (76). Data to be supplied to the condenser abnormality degree calculation unit (75).

As a result, the degree of abnormality obtained from the condenser degree-of-abnormality calculation unit (75) becomes a more accurate value, and it becomes possible to determine the abnormality by the instantaneous value thereof.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. Further, the configuration of each part of the present invention is not limited to the above embodiment, but various modifications can be made within the technical scope described in the claims.

For example, the degree of abnormality is not limited to that defined by the above equation 4, and it goes without saying that various evaluation values that reflect a decrease in the heat exchange rate of the condenser can be adopted.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an absorption refrigerator according to the present invention.

FIG. 2 is a block diagram showing a configuration of a failure diagnosis system.

FIG. 3 is a block diagram showing another configuration example of the failure diagnosis system.

FIG. 4 is a graph showing a comparison between measured and estimated cooling water flow rates.

FIG. 5 is a graph showing a relationship between a heat exchange amount and a logarithmic average temperature difference.

[Explanation of symbols]

 (11) Condenser (12) Low temperature regenerator (21) Evaporator (22) Absorber (3) High temperature regenerator (4) High temperature heat exchanger (5) Low temperature heat exchanger (6) Sensor group (7) Calculation Processing circuit (8) Output device

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masahiro Furukawa 2-18 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kazuhiro Yoshii 2-chome Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. An absorption chiller in which a condenser (11), an evaporator (21), an absorber (22) and the like are connected to each other by piping to form one refrigeration cycle, and the heat of the condenser (11) is A system for diagnosing an abnormality of a refrigerator based on a decrease in exchange rate, the first data processing means deriving temperature difference data according to a temperature difference between two media flowing into a condenser (11), Temperature difference data and condenser (1
Storage means storing the correspondence with the heat exchange amount in 1), flow rate Vc of cold water flowing into the evaporator (21), and cold water inlet temperature T
c_in, cold water outlet temperature Tc_out, temperature of cooling water flowing from the absorber (22) to the condenser (11) (cooling water intermediate temperature) T
co_mid and second data processing means for estimating the cooling water flow rate Vco based on the measured data of the inlet temperature Tco_in of the cooling water flowing into the absorber (22), the estimated cooling water amount Vco, and the condenser ( 11) based on the measured data of the outlet temperature Tco_out of the cooling water flowing out from 11) and the cooling water intermediate temperature Tco_mid
Fourth data processing means for deriving normal temperature difference data corresponding to the calculated heat exchange amount based on the correspondence between the third data processing means for calculating the heat exchange amount in (11) and the storing means. And comparing the temperature difference data in the normal state with the temperature difference data in the failure diagnosis obtained from the first data processing means,
A failure diagnosis system for an absorption chiller, comprising: fifth data processing means for determining the degree of abnormality of the condenser (11); and output means for outputting the determination result of the fifth data processing means. 2. The estimated data of the cooling water flow rate Vco obtained from the second data processing means is subjected to moving average processing over a predetermined time, and the result is sent to the third data processing means as the estimated cooling water quantity Vco. The fault diagnosis system according to claim 1, comprising a sixth data processing means.