What is Net Refrigeration Effect (NRE)?
Net refrigeration effect (NRE) is the quantity of heat that each pound of the refrigerant absorbs in the refrigerated space to produce useful cooling. That’s a pretty vague definition. We know that it’s an amount of heat in processes that take place within the evaporator. Still, the phrase “useful cooling” seems rather broad. Even though […]
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How to Send Heat to Outer Space – What Ancients Knew That You Don’t
You likely already know a bit about radiant heating from your education and work in the HVAC industry. Science textbooks like to use the sun and campfires as classic examples of radiant heat transfer. We also have plenty of heating devices with radiation right in the name, such as water radiator heaters and radiant space […]
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What is Compressor Volumetric Efficiency?
Simply stated, a compressor’s volumetric efficiency (VE) is a compressor’s ability to pump the most pounds of refrigerant over time. The compressor’s function is right in the name: it compresses gaseous refrigerant. After compression, the gas moves on to the condenser and continues the refrigeration cycle. However, some of the refrigerant vapor that enters the […]
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The Misunderstood Lockout Relay
Educators love lockout relays and we also love pretending you will still see them out in the field all the time. Sometimes I have to look myself in the mirror in the morning and sadly repeat “lockout relays are dead” several times before the reality sinks in. before I get the emails… they aren't COMPLETELY […]
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Understanding Heat Transfer
Heat is a byproduct of mechanical energy that presents itself as a temperature increase. French physicist James Prescott Joule aimed to equate heat to mechanical energy. Early experiments used paddle-like structures to stir water within a container and raise its temperature. The paddles would move and agitate the water whenever a mass on a pulley […]
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False Alarms: The Legacy of Phosgene Gas
We’ve all been in the unenviable position of unsweating a compressor and getting blasted in the eyes with a waft of gas that smells like burning sulfur from the pits of Hades. As we stagger back, covering our nose and holding our breath, memories of the phrase “phosphene gas” from trade school or World War […]
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