Talk:Steam engine/Comments

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I have been trying edit this article over the past six months and quite frankly it is a tangled mess. I have come up against such intractable fundamental problems that all that I have been able to do so far is to add some factual input to the early historical material. Even the subject "steam engine" itself is ill-defined: for instance I am at present trying to clarify the initial statement, presumably intended as some sort of "disambiguation": "the term steam engine may also refer to an entire railroad steam locomotive". Well this does not just apply to locomotives: in many cases the term can signify a whole steam unit, including the steam generator and motor or as in this article, specifically to the steam "motor" (or "engine part"). The problem is that the many different types of boilers can be combined with many different types of "motor". The implication of this is that when we talk of "efficiency" we can be referring to any one of three things: the boiler, the engine part, or the two combined into a unit. Surely in each case we have to approach the problem differently: in the first case we are dealing with combustion, and heat transfer, in the second with fluid dynamics and expanders - in the third with work obtained from a given heat input (where, for example, if we wish we can compare it with Carnot's ideal engine). Confusion between the three distinct aspects leads to ludicrous statements like the following in the "efficiency" section. "One source of inefficiency is that the condenser causes losses by being somewhat hotter than the outside world. Thus any closed-cycle engine will always be somewhat less efficient than any open-cycle engine, because of condenser losses." This does not stand close scrutiny, as any steam engineer will stress the importance of maintaining feedwater temperature above a certain level . Warm condensate is most often recycled back to the boiler – and this in the interest of economy! - because it is perfectly obvious that less heat energy is needed to return warm water to working temperature than cold - so how do we square this circle? As I say the subject of the present article is limited to the steam engine viewed as an expander unit. It is not about the whole integrated system, so I would question whether in this context it is valid to discuss overall thermal efficiency at all. Anyway, where do we go from here?--John of Paris 08:11, 25 May 2007 (UTC)