What is latent heat?

Latent heat refers specifically to the energy required to change the state of a substance without changing its temperature. This process occurs during phase transitions, such as melting, freezing, vaporization, or condensation. For example, when ice melts into water, it absorbs heat energy (latent heat of fusion) without a rise in temperature until the entire substance has transitioned into the liquid state.

Understanding latent heat is crucial in HVAC applications because it plays a significant role in refrigeration and air conditioning systems. These systems rely on the principles of latent heat to transfer heat from inside a space to the outside environment, effectively removing heat in order to cool the indoor air.

The other options do not accurately describe latent heat. The energy required to raise temperature pertains to sensible heat, which is the heat that changes the temperature of a substance. Heat lost through conduction refers to the transfer of heat between materials that are in direct contact. Heat that is stored but not used could describe other forms of energy but is not a specific definition in thermodynamics related to phase changes. By understanding latent heat, one can better grasp how HVAC systems operate efficiently by managing heat transfers and state changes in refrigerants.