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Sensible heat is the name for energy in the form of heat that brings about either an increase or a decrease in temperature. Its name comes from the fact that it can be sensed as a change in temperature. Transfer of this type of heat energy occurs as either conduction or convection.
Addition of this form of heat results in a temperature increase whereas its removal results in a temperature decrease. It is distinguished from latent heat, which does not change the temperature of a substance. Rather, latent heat is heat that is exchanged between a substance and its surroundings during a phase change that occurs at a constant temperature, such as solid ice melting into liquid water.
Various techniques may be used to measure or estimate sensible heat depending on the particular circumstances. In very simple cases, such as measuring the increase in temperature of a substance in a kitchen or laboratory, a thermometer may be all that is necessary. This would not be practical on very large scales such as in measuring the sensible heat flux, or heat transfer per unit of area over time, of a large geographical region. For such situations, sensible heat flux may be estimated using a statistical method known as eddy covariance, or measured by an optical device known as a large aperture scintillometer.
Sensible heat is of interest in fields such as meteorology and climatology where it is used in near-term weather forecasting calculations and long-term climate modeling. The surface of the earth absorbs heat from the sun in the form of radiation and converts it to both sensible and latent heat. Its conversion to sensible heat results in changes in the temperatures of the earth’s surfaces, both land and water, and of its atmosphere.
Another field where this form of heat is of significance is heating, ventilation, and air conditioning (HVAC). Sensible heat load is one factor that determines the necessary temperature of the air supplied to a room and the required rate of airflow to maintain the desired room temperature. It may be used for HVAC calculation purposes in the form of the sensible heat ratio (SHR), which is the amount of sensible heat divided by the total amount of heat in a given space. HVAC equipment is selected such that the SHR of the system is compatible with the SHR of the room or building for which it will be used.
Sensible heat can also be stored for later use by raising the temperature of a material that will later release that heat for use when desired. For example, solar energy may be concentrated and stored this way during daylight hours and then drawn for use from storage during hours when the sun is not shining. Materials that may be used as storage media depend on the storage temperature, the size of the system, and other factors. They may include such diverse materials as water, various types of stones, molten salts, liquid metals, and more.
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