What does the term 'sensible heat' refer to?

The term 'sensible heat' refers to the amount of heat that causes a change in temperature of a substance without changing its state. This heat can be sensed and measured using a thermometer, which makes option A the most accurate definition. When sensible heat is added to a substance, such as air or water, its temperature increases, and this increase can be tracked with temperature-measuring instruments.

In contrast, the other options do not accurately represent the concept of sensible heat. While heat that is felt but not seen might refer to latent heat or other forms of thermal energy, it is less precise than the terminology of sensible heat. Heat lost through ventilation pertains more to energy losses and efficiency rather than a definition of heat itself. Similarly, heat absorbed by insulation is a specific application of heat transfer but does not define what sensible heat is. Understanding the definition and properties of sensible heat is crucial for HVAC professionals, as it directly relates to temperature control and thermodynamics in heating and cooling systems.