Device and method for detecting fouling in a shell and tube heat exchanger

A system for calculating the degree of fouling in a heat exchanger having at least one longitudinal tube inside of a shell, the shell having a first heat exchange medium flowing inside the tube and a second heat exchange medium flowing across the outside surface of the tube, said system comprising:

• a first temperature sensor associated with said tube for sensing the temperature (Ttube) of the tube at a first axial position of the tube;
• a device associated with the interior of said tube for determining the temperature of the first heat exchange medium (Tmedium) inside the tube at the first axial position of the tube;
• and
• a fouling detector coupled to said first temperature sensor and said device, for calculating the degree of fouling in the tube based on the initial temperature difference (ΔTinitiai) between the temperature of the tube (Ttube) and the temperature of the first heat exchange medium in the tube (Tfluid) at the first axial position, and a later temperature difference (ΔTlater) between the temperature of the tube (Ttube) and the temperature of the first heat exchange medium in the tube (Tmedium) at the first axial position.

A method of detecting fouling in a heat exchanger having a first heat exchange fluid flowing through a tube and a second heat exchange fluid flowing over an outer surface of the tube, the method comprising the steps of:

• sensing a first temperature of the tube at a first axial position;
• simultaneously with sensing the first temperature of the tube at the first axial position, determining a first temperature of the first heat exchange fluid in the tube at a position corresponding to the first axial position;
• calculating the difference between the first temperature of the tube and the first temperature of the first heat exchange fluid in the tube;
• sensing a second temperature of the tube at the first axial position after operating the condenser for a period of time;
• simultaneously with sensing the second temperature of the tube at the first axial position, determining a second temperature of the first heat exchange fluid in the tube at a position corresponding to the first axial position at the second point in time;
• calculating the difference between the second temperature of the tube and the second temperature of the first heat exchange fluid in the tube;
• and
• determining the fouling resistance of the tube as a function of:
• the difference between the first temperature of the tube and the first temperature of the first heat exchange fluid in the tube, and the difference between the second temperature of the tube and the second temperature of the first heat exchange fluid in the tube.