Undersökning av tryckfall relaterat till avstånd mellan två 90 graders krökar i cirkulär ventilationskanal

Sammanfattning: Due to higher standards of living around the world, greater industries and larger infrastructures causes an increase of the global energy consumption. This harvest of energy puts a great stress on the global environment. With this development, it becomes increasingly important to utilize energy resources in the best possible way. Fans are components that are often used in the industry and in households. A common problem is that the fan is oversized. An oversized fan causes an excessive flow, which has to be adjusted in order to achieve the correct flow. This results in larger energy usage than the use of a properly sized fan. When designing a ventilation system calculations have to be made in order to determine the total pressure loss of the system. A series of simplifications are applied when using theoretical calculations. The total pressure loss of the system is assumed to be the sum of the pressure loss of each component in the system. This simplification ignores the separation distance that exists between each component. In reality, when air passes through the components, swirls emerge and a distortion of the velocity profile occurs. This causes large pressure losses due to friction losses occurring between the fluid and the pipe wall. The recommendation given in HVAC installations states that two 90 degree elbows should not be placed closer to each other than 6D (D representing the hydraulic diameter of the pipe) to thereby prevent large pressure drops. This dissertation will address the following questions: The recommendation in HVAC installations states that two 90 degree elbows should not be placed closer to each other than 6D (D representing the hydraulic diameter of the pipe) to thereby prevent large pressure drops. Does this recommendation conform with the empirical data obtained from conducted experiments?  What is the relation between the pressure drop and the separation distance between two 90 degree elbows? In this dissertation a series of experiments are conducted where pressure loss measurements are made within a circular ventilation duct with two integrated 90 degree elbows. Pressure loss measurements within a U-shaped piping system are made at five different fluid velocities each at 11 different separation distances between the two 90 degree elbows. By analysis of the obtained empirical data and by comparing it to the recommendation no results were found to validate this statement.