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« Back to Glossary Index Delta (Δ) is the fourth letter of the Greek alphabet, is used as a mathematical symbol and describes the difference of any variable quantity. Examples of quantities are: P is the formula symbol for the physical pressure. Pressure indicates the force exerted by a body on a surface. Pressure is expressed in pascals (Pa). When these two pieces of information are combined, it is understood that delta p (Δp) stands for pressure difference. Use of delta p (∆p)Delta p (∆p) thus describes the pressure difference between two measured values. These values can be measured at different times or at different locations in a system. Three situations can be recorded:
Calculation of delta p (∆p)∆p = p1 — p2 Practical examples of delta p (∆p)Pressure differences can be measured in many areas. Typical examples are the pressure drop in a piping system — for example before and after a tool, a heat exchanger, a pump or a filter. A small pressure drop in these examples is due to wall friction in the systems. Unintended pressure differencesDelta p (∆p) is an important measurement of the quality of pressurized systems. Unintended changes in the pressure structure quickly have a negative impact on the functions in the system and should be noticed and corrected as soon as possible. For quick verification of pressure differences, data loggers can be used to record changes in the circuit and provide conclusions about the problem. « Zurück zum Glossar Index
For more information on pressure measurement, call Mead O-Brien at (800) 892-2769 or visit www.meadobrien.com. Here is a great video, courtesy of Ashcroft, that provides an excellent visual understanding of differential pressure.
With a few exceptions, most homes in the U.S. use some form of ducted heating/cooling system with air returns and registers located throughout the rooms in the house. The central air handler moves air from the returns back to the cooling and heating coils and then moves it back into the house to either heat or cool the indoor environment. On the return air side of the air handler where all the returns merge at one point is where the air filter is located. The filter is designed to remove all the airborne dust and dirt that is in the air. Only dust particles in the air that are pulled into the return air grills will be filtered. If the dust particles are too heavy to be airborne they will remain at rest on a surface and never reach the filter. The HVAC unit in your home is a balanced system. It is designed so that there is slightly more air moving than returning. This helps to keep the house in a positive pressure mode which eliminates in-leakage of cold or hot air. The balance also includes the ability of the blower/motor to move the air throughout the duct work as well as through the air filter. The air ducts and filter all have a resistance known as Delta P or pressure drop. The higher the pressure drop or static pressure the more powerful a blower/ motor will be required. If the air pressure is balanced with a clean air filter, once the air filter starts to load up the resistance or pressure drop across the filter ( Delta P ) will increase. If the Blower/Motor is not properly sized as the Delta P increases the air flow across the air handler decreases. Once this takes place the amount of air and amount of airborne dust that is in the air will be significantly reduced and you end up with the air handler running more often just to keep the house cool or warm and more dust in the environment. This is one reason why you need to change your air filter at least once every 6 months and more often if you live in an urban area. For more information on air filtration and how it works please go to our website at: https://www.pureairsystems.com or call us on our toll-free number at: 800-869-8025. Share On: Facebook Twitter Google Plus LinkedIn Don't miss out! Like us on Facebook, Follow us on Twitter or subscribe to our RSS Feed on Feed Burner and get our latest posts. This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more.
By closing this message or continuing to use our site, you agree to our cookie policy. Learn More This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more. ΔP stands for the difference between two measured pressure values. This can be measured either at different times/dates or at different positions in a system. The measurement at different times, can be a continuous measurement from day to day to see a trend as the ΔP develops over a longer period of time. Measurement at different positions in a system, i.e. you compare the pressure at the input with the pressure at the output of a machine. And get the pressure drop - Delta P. In a piping system or a heat exchanger with a moving fluid, the pressure usually drops due to friction. The friction happens in between the water and the contacting surfaces, e.g. the pipe wall. As higher the differnce, as more likely there is fouling in the system. The ΔP in the heat exchanger to the left can be calculated very simple. Subtract the inlet pressure (P1) at the point B, from the outlet pressure (P2) at the exit A and you will get Delta P. The equation for the pressure difference is: ΔP = P2 – P1 It is obvious that a high concentration of deposits, in pipe or exchanger, lead to a high pressure drop, ΔP. If there are deposits the water can't flow free. Hence the outlet pressure is much lower than the inlet pressure. Examples about delta P the differential pressureIf you are sitting in an airplane and drink from a plastic bottle, then the pressure in the bottle is the same as in the airplane. Once you have landed you will notice that the bottle is pushed inwards. That's because the pressure in the plane is much lower than the atmospheric pressure at the ground. This pressure difference can be seen on the bottle. The delta P would be the difference in between the lower pressure in the airplane and the normal pressure on the ground. We at Merus use delta P for the performance monitoring. After the installation of Merus Rings the delta P decreases, if all works well to its design level. |