I have been flirting around with only shell and tube heat exchangers, for the last 40 years, been checking on their health from time to time. But with all said and done, it’s easier to conquer a woman’s heart than a heat exchanger…!

The design of Heat Exchanger is complicated, much like a human being. Every human being is different by nature and also, in how he or she reacts to different situations. Similarly, it is difficult to understand the situation in a heat exchanger in totality. So, how does one design a heat exchanger? How does one know the kind of fouling – Biological algae, the sticky substance that sticks on the inner and outer surface of the tubes? Exactly like the LDL that sticks on the inner surface of the arteries carrying blood. The other kind of fouling, more like debris, is like HDL – the scavenger that cleans up the tube/arteries. If the debris is not sufficient and the clogging takes place, it may lead to an increase in pressure in that zone. This may lead to failure causing rapture and leakage in the heat exchanger joints, similar to heart attack in the human bodies.

Heat Exchanger is quite similar to God’s creation

Although a lot of research has been done, this cannot be confined to an empirical formula or correlations obtained from experiments.

For that matter, although, so much research has been done on the human body, we still don’t know everything about it. Every now and then, a new disease crops up as a challenge for the experts to find a solution to. Then we find newer techniques on how to optimise on health and skills. Heat exchanger is quite similar to the God’s creation in that regard. The skills required to maintain the exchanger can become as complicated. Companies and organizations like IOCL and HTRI, together, have a wealth of knowledge.

I have been flirting around with only shell and tube heat exchangers, for the last 40 years, been checking on their health from time to time. But with all said and done, it’s easier to conquer a woman’s heart than a heat exchanger.

Heat Exchanger is static equipment but only on the surface; there is tremendous movement inside. More like the universe, where there is so much of movement and yet static with such harmony and peace; It is still extremely unpredictable, much like a heat exchanger.

Design of a Heat Exchanger

This heat transfer equipment cannot be designed with correlations and empirical formulae, the design can only evolve.  The designer has to understand that it is close to nature.  Heat transfer between two bodies is a most natural phenomenon. It has its presence just about everywhere; it is omnipresent – from radiators in the car to refrigerators. Specific to the Shell and tube type, there are cooler, condenser, heater, boiler, vaporiser, gasifiers, liquefiers and many more. Shell and Tube heat exchangers are present in all types of plants – chemical, petrochemical, oil refineries, fertiliser, power, nuclear etc.

It is the most challenging to design for the simple reason that the variables are too many and it is very difficult to confine them to empirical formulae and correlations obtained from research. The most worrisome would be for dirty service e.g. in refining for petroleum products, the crude which is with dirt is never consistent and hence, the Renault number taken in the thermal design cannot be relied upon. Furthermore, any mishaps or inconsistency in the plant, such as malfunctioning of the smallest equipment like valves, will greatly affect the performance of the heat exchanger, both in heat transfer and mechanical functioning, as both are interlinked.

The most difficult to predict is also the one in a dirty service. The dirt is also like the cholesterol in the blood the LDL that’s bad and responsible for all the fouling and the HDL the good one that’s the scavenger that eats up the bad. There is the dirt that sticks to the walls of the tube and the other one the non sticky, hard and solid that actually removes the soft sticky one from the walls.

More like a plumbing system right there in your body, where the roughage will clean up your system: the intestine on one hand and the arteries on the other.

Copyright © 2020 Haresh Sippy

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