Which type of heat is added to a substance without increasing its temperature?

Latent heat refers to the heat energy that is absorbed or released by a substance during a change of state, such as transitioning from solid to liquid (melting) or liquid to gas (vaporization), without a change in temperature. This process is crucial in various HVAC applications, as it affects how refrigerants and other fluids behave within the system when they undergo phase changes.

When water boils, for instance, it absorbs latent heat, which allows it to change from liquid to vapor without increasing its temperature until it is fully converted into steam. This principle is foundational in understanding how energy transfer occurs during these phase changes, which is essential for efficient system design and operation in heating and cooling mechanisms.

Other types of heat, such as sensible heat, involve changes in temperature without a change in state, which is not applicable in this context.