Cooling Theory

SKU: RVI-11476Duration: 20 Minutes

How do you properly cool a building? Cooling systems are used to cool and condition the air in rooms and building. To do this, they must remove heat from the air. How much heat needs to be removed to reach the desired temperature? What about humidity - the amount of water vapor in the air? Humidity affects how much heat we feel so it must also be addressed. This interactive online course will address these and other cooling system-related topics and issues.

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Glass vessel of water heated by a burner showing how much BTUs it takes to completely vaporize the water.

Measuring device (sling psychrometer) being used to gauge the enthalpy in air.

Diagram demonstrating how boiling temperatures are reduced at higher elevations, due to less atmospheric pressure.

Course Details

Specs

Training Time: 20 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English

Learning Objectives

State the First Law of Thermodynamics
Understand that Total Cooling must take into account Sensible Heat and Latent Heat
Identify that a thermometer measures sensible heat
Identify that a sling psychrometer measures relative humidity
Define "Enthalpy" and identify the properties of air that influence enthalpy

Key Questions

The following key questions are answered in this module:

What is the definition of "heat"?
Heat is a measure of the warmth or coldness of a substance, usually in reference to a standard. Heat is also a form of energy. Heat energy, or thermal energy must be added or removed to change the temperature of the air in a building

What is the First Law of Thermodynamics?
The First Law of Thermodynamics, also called the Law of Conservation of Energy, states that energy cannot be created or destroyed; it can only change form.

What is Sensible Heat?
Heat that results in a temperature change only, with no change in phase. It is the heat in a substance, such as air, that can be "sensed" by you and a thermometer.

What is Latent Heat?
Heat that is used to change the phase of a substance - for example, from a solid to a liquid, or a liquid to a gas. The water vapor in air contains latent heat.

How do you measure the capacity of a heating or cooling system?
The capacity of a heating or cooling system is commonly reported in BTUs. One BTU, or one British thermal unit, is defined as the amount of heat required to heat one pound of liquid water by one degree Fahrenheit.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

Air is a mixture of gases and water vapor that contains two types of heat: sensible heat and latent heat. “Sensible heat” is defined as heat that results in a temperature change only, with no change in phase. It is the heat in a substance, such as air, that can be “sensed” by you and a thermometer. When a solid melt or a liquid boil, it absorbs heat, but that heat is used to change the phase of the substance; the temperature of the substance does not change. “Latent heat” is heat that is used to change the phase of a substance – for example, from a solid to a liquid, or a liquid to a gas. The water vapor in air contains latent heat. Latent heat is not sensed by a thermometer, but you feel it because people rely upon latent heat for cooling. When we are hot, we perspire and the sweat on our skin evaporates into the air around us. The heat required for this phase change, from liquid to gas, cools us down. When the air around us is humid (when it contains a lot of water vapor), our sweat evaporates at a slower rate. This is why hot humid air “feels” hotter than hot dry air. It is also why HVAC systems must account for sensible heat and latent heat, and control both temperature and humidity. The Second Law governs how air is cooled in an AHU; heat is removed from the air by passing it through a coil that is cooler than the entering air.

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