Heat exchanger noise problem

[remp]

I have a brazed plate heat exchanger with hot water on the primary side 130/115 Deg C and 80/70 Deg C water on the secondard side.

When both sides are pumping there is a constant noise from the unit as if there is a nut or piece of metal in the Heat exchanger trying to get thro. We have checked the hot side for debris but nothing in there.

When the cold side pump is siwtched off and the hot side running the noise goes away immediatly. So we thought it must be debris in the cold side. However if the cold side is running and the hot side is turned off the noise also goes away also.

The noise must be something to do with heat and water flow on both side. No flow on either side and the noises goes away... anyone knows what is going on?>????

 

[BronYrAur]

I would suspect that your are vaporizing some of the cold water as it enters the heat exchanger and comes in contact with the 130 deg C surface. When the steam bubbles collapse, you get a knocking noise. Conduct a test and turn off your heat source (or lower it to below 100 deg C) and and see if you get any noise.

 

[Compositepro]

You may also have dissolved gases in the water which means that bubbles will form at lower temperatures than you would expect.