One of the most fundamental principles that has an integral role in the HVAC/R industry is heat: what it is, how it is transferred, and its different forms. Heat is defined by the laws of thermodynamics. Temperature, which describes the level of heat with reference to no heat, is quantified by temperature which is related to heat content defined by the British thermal unit (BTU).

Specifically, the BTU is defined as the amount of heat required to raise the temperature of 1 lb. of water 1°F. Heat is transferred in one of three ways: conduction, convection, and radiation – sometimes in a combination of these methods simultaneously. When a change in temperature can be registered using one or more of these methods, it is known as sensible heat; conversely, latent heat or hidden heat occurs when there is heat added or taken away which results in a phase change but with no change in temperature. The specific affect heat has on a substance refers to as its specific heat.

Coupled with this general core concept of heat is pressure and how the two relate to one another. Pressure is defined as force per unit of area; expressed as pounds per square inch (psi). For reference, a column of water 1 ft. high exerts 0.433 psi at the bottom. Barometers are instruments used to measure atmospheric pressures in inches of mercury; two of the most commonly used types of barometers are the mercury and the aneroid. As it relates to use in HVAC/R, pressure gages have been designed and implemented to measure pressure in enclosed systems like most refrigeration cycles.

There are two commonly used types of pressure gages, the compound gage and the high-pressure gage. A compound gage reads both above and below atmospheric pressure. In closed refrigeration cycles, it is helpful to note that temperature are not mutually exclusive, meaning that if you know one then you know the other. Pressure is measured in psi and kilopascals (kPa), wherein 1 psi is equal to 6890 pascal, or 6.89 kPa. As you can see, these concepts of heat and pressure are crucial fundamentals to grasp when working in the air conditioning, heating, and refrigeration industry as they work in tandem with one another, bound by the laws of physics and thermodynamics.

As you can see, these concepts of heat and pressure are crucial fundamentals to grasp when working in the air conditioning, heating, and refrigeration industry as they work in tandem with one another, bound by the laws of physics and thermodynamics. Are you an individual that has both experience working with and an understanding of how these concepts work? Do you feel an enriching career in commercial HVAC/R will have its rewards for you? Reach out to us today via the link below and let us know a little about yourself.

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