Heat exchanger monitoring system

1. A heat exchanger monitoring system comprising:

a heat exchanger for receiving a flow of a working fluid therethrough;

a first sensor for measuring a property relating to an amount of contaminant material carried by a first flow of fluid entering the heat exchanger and configured to output a first sensor signal indicative of the measured property relating to the amount of contaminant material carried by the first flow of fluid;

a second sensor for measuring the same property relating to an amount of contaminant material carried by a second flow of fluid exiting the heat exchanger and configured to output a second sensor signal indicative of the measured property relating to the amount of contaminant material carried by the second flow of fluid; and

a monitoring device configured to receive and compare the first and second sensor signals to thereby determine a variation in the property relating to the amount of contaminant material carried by the fluid as it passes through the heat exchanger.

2. A heat exchanger monitoring system as claimed in claim 1 comprising a reference database containing values for converting the sensor signals into information regarding one or more contaminant types and a concentration of the one or more contaminant types in the working fluid.

3. A heat exchanger monitoring system as claimed in claim 2 , wherein the monitoring device is configured to output:

a) a first output signal if the concentration of contaminants measured by the first sensor is greater by a first predetermined amount than the amount of contaminants measured by the second sensor;

b) a second output signal if the concentration of contaminants measured by the second sensor is greater by a second predetermined amount than the concentration of contaminants measured by the first sensor; and

c) a third output signal, or no output signal, if the criteria for outputting the first output signal and second output signal are not met.

4. A heat exchanger monitoring system as claimed in claim 2 , wherein the monitoring device is configured to output an upstream wear signal if the concentration of contaminants measured by the first sensor is above a predetermined threshold.

5. A heat exchanger monitoring system as claimed in claim 1 , wherein the monitoring device is arranged to record changes in the first and/or the second sensor signal over time.

6. A heat exchanger monitoring system as claimed in claim 1 , wherein the first and second sensors are capacitive sensors.

7. A heat exchanger monitoring system as claimed in claim 1 , comprising:

a first housing for receiving the first sensor and a second housing for receiving the second sensor.

8. A heat exchanger monitoring system as claimed in claim 7 , wherein the first and second housings are each located on a flow line external to the heat exchanger.

9. A heat exchanger monitoring system according to claim 1 , wherein the heat exchanger is at least partially constructed by an additive manufacturing method.

10. A heat exchanger monitoring system according to claim 9 wherein housings for the first and second sensors are integrally formed with the heat exchanger.

11. A method of monitoring a heat exchanger, the heat exchanger being for receiving a flow of fluid, the method comprising:

using a first sensor, measuring a property relating to an amount of contaminant material carried by a first flow of fluid entering the heat exchanger;

thereby obtaining a first sensor signal indicative of the measured property relating to the amount of contaminant material carried by the first flow of fluid;

using a second sensor, measuring a property relating to an amount of contaminant material carried by a second flow of fluid exiting the heat exchanger;

thereby obtaining a second sensor signal indicative of the measured property relating to the amount of contaminant material carried by the second flow of fluid; and

comparing the first and second sensor signals to thereby determine a variation in the property relating to the amount of contaminant material carried by the fluid as it passes through the heat exchanger.

12. A method of monitoring a heat exchanger as claimed in claim 11 , comprising:

converting the sensor signals into information regarding one or more contaminant types and a concentration of the one or more contaminant types in the working fluid.

13. A method of monitoring a heat exchanger as claimed in claim 11 , comprising:

outputting a first output signal if the concentration of contaminants measured by the first sensor is greater by a first predetermined amount than the amount of contaminants measured by the second sensor;

outputting a second output signal if the concentration of contaminants measured by the second sensor is greater by a second predetermined amount than the concentration of contaminants measured by the first sensor; and

outputting a third output signal, or no output signal, if the criteria for outputting the first output signal and second output signal are not met.

14. A method of monitoring a heat exchanger as claimed in claim 11 , comprising:

outputting an upstream wear signal if the concentration of contaminants measured by the first sensor is above a predetermined threshold.

15. A method of monitoring a heat exchanger as claimed in claim 11 , comprising:

monitoring the first and/or the second sensor signal over time and recording changes in the sensor signals with time.