Fans Ventilation A Practical Guide

W T W (Bill) Cory

In an age when political correctness has become the state religion, it is perhaps courting disaster to tell a joke about our fellow human beings. That it might be interpreted as racist by the professional do-gooders is doubly worrying. However, as a man of English-Scottish ancestry and with Welsh-lrish wife I feel impervious to such slings and arrows.

“Excuse me, my good man”, said an Englishman lost in the wilds of Ireland. “Can you tell me the way to Ballykelly?” “If I were you, sir, I wouldn’t start from here."

A perfectly correct and helpful answer. It’s just the same with the fan world. We shouldn’t have started when and where we did. But the die was already cast and aline from there to the present day shows us the path we trod. There were numerous setbacks and diversions, but an extension of that line, shows us the direction to the future. If we have studied that history, we may even avoid making the same mistakes twice, and will not have to suffer the old “Codger” in the corner saying “We tried that in 1961 and it didn’t work”.

To maintain the interest of those who like to classify and define, the Chapter continues with a description of the various fan types in what is hopefully a logical progression. It describes the shape of the characteristic curves, but the reader’s patience will be rewarded in the Chapters that follow.

It is inevitable that the content of this chapter will reflect the per­sonal experiences, and indeed preferences, of the author. Apologies are, therefore, proffered in advance to those compa­nies whose products are conspicuous by their absence. The privilege of all historians is to be able to “slant” the investiga­tions to suit their own individual prejudices — and I am no exception.

Mechanical fans are a particularly mature product — they have been around, and running most of the time, since at least the sixteenth century. Engineers will be the first to acknowledge that nothing is new, and most of the major design principles had been established by the early twentieth century. We, who have followed, have merely improved, tinkered with, or fitted theories to that which our fathers invented. We are but pygmies, stand­ing on the shoulders of giants.

To appreciate the present and future developments, it is essen­tial to know something of the past. Where we have come from gives us a direction as to where we might go in the future. It may also help to explain why there are so many different types of fan. The reasons for their existence are invariably that they met a customer need. Whilst managing directors may complain that they have half a million models in their manufacturing range, the chief engineer may reflect that if he or she were to meet all the requirements of flowrate, pressure and efficiency in the presence of hot, erosive and/or corrosive gases then an even larger range might be desirable.

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