One of humankind’s most significant achievements has been the ability to generate heat and guide its movement for useful purposes. This ability is essential to modern life, especially when it’s used to establish and maintain thermal comfort in habitable spaces. Heat exchangers of all types are used for this purpose.
For centuries, heat was generated from fire, and methods were developed to guide that heat into occupied areas of buildings. An often-cited example of early heat exchange for improving human comfort was the Roman hypocaust. Wood-fueled fires would be maintained outside of occupied spaces. The hot combustion gases from these fires were channeled through spaces under stone floors supported on stone columns, as seen in Figure 1-1, as well as through hollow stone walls.