What Is A Btu?

A Btu, or British Thermal Unit, is a traditional unit of energy and is a measure of the heat content of fuels.

Originally, the Btu was the amount of energy needed to increase the temperature of 1 pound of liquid water by 1 degree Fahrenheit.  The term became common among engineers in the late 1800’s.

A single Btu is insignificant in terms of the amount of energy used by a single household or by an entire country. In 2013, the United States used about 98 quadrillion (written out, 1 quadrillion is a 1 followed by 15 zeros) Btu of energy.

One Btu is approximately equal to the energy released by burning a match.

Match

Interesting Energy Conversion Factors

Energy source Physical units and Btu (averages,¹ 2012)
Electricity 1 kilowatt hour = 3,412 Btu
Natural gas 1 cubic foot = 1,025 Btu
Motor gasoline (10% ethanol) 1 gallon = 120,524 Btu
Diesel fuel 1 gallon = 138,690 Btu
Heating oil 1 gallon = 138,690 Btu
Propane 1 gallon = 91,333 Btu
Wood 1 cord = 20,000,000 Btu (Estimated)

1Weighted averages across different contexts of each fuel such as imports, exports, production, and consumption. Source:  www.eia.gov/EnergyExplained by the U.S . Energy Information Administration

EXAIR manufactures the Cabinet Cooler System.  The Cabinet Cooler System is a low cost, reliable way to cool and purge electronic control panels.  They incorporate a vortex tube to produce cold air from compressed air – with no moving parts! EXAIR Cabinet Cooler Systems are available for NEMA 12, 4, and 4X type enclosures.  For the most efficient way to operate Cabinet cooler, a thermostat control system would be utilized. The standard thermostat control systems include an adjustable thermostat factory set at 95F.  Also, available is the ETC Electronic Temperature Control, providing precise control with easy adjustability and a digital readout.

Cabinet Cooler Family
EXAIR Cabinet Cooler Systems

In the United States, the power of HVAC (Heating Ventilating and Air Conditioning) systems is often expressed in BTU/hr.

The EXAIR Cabinet Cooler Systems are available with cooling capacities ranging from 275 to 5,600 Btu/hr.  To cool the down the equivalent of 98 quadrillion Btu’s of energy used by the US in 2013, it would take 17.5 trillion of our largest Cabinet Cooler Systems!

If you would like to find out how many Btu’s of cooling your electrical cabinet needs, please fill out and send in the Cabinet Cooler Sizing Guide and we can let you know.

Brian Bergmann
Application Engineer
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Match Photo courtesy of Samuel M. Livingston via Creative Commons License

The Heat is On!

Well, it is here.  The middle of summer cannot be denied in Cincinnati this week.  We have had a high temperature of at least ninety degrees the last five days with near 100% humidity.  These are the days when you have to either work very earlier in the morning or very late at night to get any yard work done.  You’ll notice that the most of our blogs the last couple weeks have been about keeping things cool, like Cabinet Cooler systems, or High Temperature Cabinet Coolers.  I’m not one to buck a trend, so I’m going to talk about cooling as well, but I will talk about cooling a manufactured product.

A customer this week was designing a new plastic extrusion system and he needs to quickly cool four plastic extrusions strands from 400 degrees Fahrenheit to 120 degrees at a fairly high feed rate.  In the past the customer had used an immersion bath followed by a blow off station using EXAIR’s Air Knives, Air Wipes, or Super Air Nozzles depending on the plastic extrusions geometry.  The immersion bath would use the specific heat of the water to quickly take away the heat from the extruded plastic.  This process had worked well for him in the past, but the immersion bath was expensive to build and maintain.  For these reasons, he was looking for an alternative.

What is going to cool better than water?  The water in the immersion bath has a very high specific heat, which is what makes it such a good material for cooling large amounts of heat very quickly.  Specific heat is the amount of energy it takes to raise 1 pound of mass 1 degree Fahrenheit.  One British Thermal Unit (BTU) is the amount of energy it takes to heat or cool one pound of water one degree.  A BTU is 1,055 Joules, which is a very high specific heat compared most other common materials.  So we can’t change the immersion liquid, but could we come up with a better process?

Well of course we can.  We can use both the specific heat of water and the latent heat of water.  The latent heat is the amount of energy water takes to evaporate.  The latent heat of water is 970.4 BTU per pound.  If we can use both the specific heat of water and the latent heat of water, we can increase our cooling and not need a large, expensive immersion bath.  The customer came up with the idea of using Atomizing Spray Nozzles and a blow off station to get the same amount of cooling but without needing a water bath.  By spraying a fine mist of water onto the extrusions, we create almost the same amount of conduction with the water and the plastic.  The water takes out the energy of rising from room temperature to its boiling point, then takes out the energy of evaporating, and then the air dries the remaining water and takes away any more heat that may be remaining.

Dave Woerner
Application Engineer
davewoerner@exair.com
@EXAIR_DW