Significance of pressure
The cold and hot fluid inlet and outlet temperature and ΔP of the fluids across the heat exchangers are very significant in determination of the health of that heat exchanger. In condensers ΔP is shown as vacuum. Any increase in ΔP or decrease in vacuum is an indication of fouling or decrease in flow rate of the fluid.
Increase in ΔP for hot fluid when the inlet hot fluid P remains same, across a heat exchanger could be due to fouling on the heat-exchanging surface exposed to the hot fluid. The same applies to CW side. An increase of ΔP with an increase in inlet P is very much possible.
In condensers the decrease in vacuum could be due to fouling on heat-exchanging surface on both or either side. Most probably it will be due to fouling of heat-exchanger surface on CW side. In condensers the decrease in vacuum could also be due to leakage from the heat-exchanging surface or from the surface exposed to atmosphere.
It is important to know the design pressure on both sides (hot & cold). The high-pressure fluid may ingress in low-pressure fluid. Normally the hot fluid pressure is higher than cold fluid pressure.
| Change in ΔP | Indication |
| Increase, in hot fluid | Increase in flow-rate of hot fluid
Fouling on HE surface on hot-fluid side |
| Decrease, in hot fluid | Decrease in flow-rate of hot fluid
Leakage on hot fluid path. |
| Increase, in cold fluid | Increase in flow-rate of cold fluid
Fouling on HE surface on cold-fluid side |
| Decrease, in cold fluid | Decrease in flow-rate of cold fluid
Leakage on cold fluid path. |
It is important to know the design pressure on both sides (hot & cold). The high-pressure fluid may ingress in low-pressure fluid. Normally the hot fluid pressure is higher than cold fluid pressure.