Water is a ubiquitous substance on Earth that is colorless, odorless, and non-toxic. It undergoes three different states of change, including solid, liquid, and vapor, depending on temperature. In an ideal state, water freezes into a solid state at 0 ℃, with a smaller specific gravity. When we heat the ice, the temperature does not immediately rise and remains at 0 ℃. It needs to absorb a latent heat of dissolution of 80kcal/kg before it slowly turns into water at 0 ℃, forming a state of coexistence of solid and liquid phases. When liquid water completely turns into 0 ℃ saturated water, adding 1 kilocalorie (kcal) of heat will increase the temperature of 1 kilogram (kg) of water by 1 ℃. Continuing to heat will gradually increase the temperature of the water, and the continuous injection of enthalpy will increase the water temperature to 100 ℃. The temperature change process from 0 ℃ water to 100 ℃ water is called sensible heat (visible heat), which can be displayed on a thermometer. The specific heat of water is 1 kcal/kg, which requires 1 kcal of heat to increase the temperature of 1 kilogram of water by 1 ℃. At 1 atmospheric pressure, when the liquid water temperature reaches 100 ℃, the water begins to boil, known as the boiling point. Continue to provide heat, but the water temperature does not increase. Water gradually changes into gas and undergoes a phase change (from liquid to gas), which is the phenomenon of latent heat of water evaporation (which absorbs heat but cannot see temperature changes on the thermometer). The heat of latent heat of evaporation is very huge, at 539 kcal/kg, which is about 5.4 times the sensible heat (100 kcal/kg).

The increase or decrease in sensible heat enthalpy can clearly indicate temperature changes

The increase or decrease in latent heat enthalpy does not show a change in temperature;

Known as latent heat of vaporization and liquefaction

At 1 atmospheric pressure:

The liquid specific heat of water is 1kcal/kg ℃

The latent heat of water dissolution is 80kcal/kg ℃

The latent heat of vaporization of water is 539kcal/kg ℃

In the humidification industry, it is to try to use external energy to convert liquid water into vapor water, and then use external force to deliver it to the space that needs to be humidified.