Fundamentals of steam heating systems

Many of the most commonly used textbooks on HVAC design used in undergraduate courses in engineering schools today do not even have a chapter on steam system design. This may appear perfectly logical since so few new buildings are being designed with steam heat. It would be unfortunate, however, if the lack of understanding of steam dynamics were the driving force in the continuing decline of the use of steam. As an intermediate thermal fluid (that is, a fluid that transfers heat over distance from a high-temperature source to lower-temperature receiver), steam has many advantages over a single-phase fluid such as water or air. The purpose of this article is to present a discussion of the physics of two-phase flow specifically as it relates to steam heating systems. Some of the concepts presented will be inconsistent with past practices in steam system design simply because they have been updated from publications and concepts based upon 1930s technology.