2019 AHR Expo

Just returned from attending the Air Conditioning, Heating, and Refrigeration Expo held in Atlanta Georgia.  Some of the biggest names in the HVAC industry, such as Carrier, Trane, and York, were in attendance.  Along with cooling and heating equipment, those manufacturers that make specialty items such as boilers, compressors, piping, controls, motors and refrigerants were also in attendance.  Visitors, as well as vendors, came from all over the world to see new product lines as well as to showcase their products.  The trend, as has been the case for several years now, is to make machines more energy efficient.  Incorporating electronics to measure different parameters such as temperature and pressure, is now routinely done.  Depending on the type of equipment, manufacturers are also offering options on how the equipment is monitored.  Some owners prefer to let their on-site personnel keep up with the operation of their equipment while others are connected by internet to a servicing agency.

No matter how efficient or how well built a machine is, it will eventually fail.  Hopefully, when it does, there won’t be any property damage or personal injury.  But if there is,  the information collected during the Expo on various products will be invaluable in helping to determine the cause of failure and subsequent damage.  More specifically, the literature can be used to help identify a machine by model number, determine the pressure limitations, or establish the power requirements.

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Runaround Coil Heat Recovery

With all the talk about green house gases and oil dependency, energy efficiency and specifically, energy savings, is a top consideration these days.  One of the things that you don’t hear about too often is something called a “runaround” coil.  The system isn’t really limited to a coil but, instead describes a very simple  system for absorbing heat from one air stream and rejecting it to another.  Consider a large office building or hospital application where 100% outside air is conditioned, distributed to the individual spaces, and then completely exhausted.  A runaround system is nothing more than two heat transfer coils, one positioned in the inlet air stream ahead of the conditioning coils, and the other in the exhaust air stream.  The two coils are connected by piping in which water or a glycol solution is circulated by a centrifugal pump, hence the name “runaround”.  During the summer when outdoor air temperatures can reach into the 90s and 100s, the fluid in the runaround system absorbs heat from the outside air and in the process, cools it to a certain temperature.  The heat carried by the fluid is then circulated to the coil in the exhaust air stream where it is rejected to the air.  Heat rejection occurs because the exhaust air is at a temperature lower than that of  the fluid stream.  Significant energy savings occur when the cooling requirements of the building can be reduced.  For example, a building without a runaround system has a 100 ton load.  In order to meet the load, the cooling equipment has to cool outside air from 95 to 55 degrees.  Precooling of the outside air by 5 degrees (90 degrees) reduces the load on the cooling equipment to approximately 87 tons.  Dropping the cooling requirement by 13 tons can result in significant electrical energy cost savings.  Now, what happens if evaporative cooling is employed in the exhaust air stream? If an evaporative cooler is added upstream of the runaround coil, then the air stream can be cooled further resulting in an increased heat transfer rate from the fluid to the air stream, further reducing the cooling capacity requirements of the cooling equipment.   The use of a runaround coil is not a novel idea but one whose time is coming.

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