PowerPoint 3: Pressure, Force, and Flow of Water PDF

PowerPoint 3 Pressure, force and flow of water LESSON INTENT Leaners will look at the different pressures in plumbing systems We will be looking at the different forces exerted in different plumbing systems Discussing how flow will be affected in our plumbing systems.  PRESSUR...

PowerPoint 3 Pressure, force and flow of water LESSON INTENT Leaners will look at the different pressures in plumbing systems We will be looking at the different forces exerted in different plumbing systems Discussing how flow will be affected in our plumbing systems.  PRESSURE, FORCE AND FLOW OF WATER SI units of pressure, force and flow Velocity Metres per second m/s Acceleration Meters per second squared m/s2 Flow rate Litres per second/minute l/s or l/m Force Newtons N Pressure Pascal (N/m2) Pa Velocity The rate at which an object changes its position , taking into account speed and direction (m/s). Acceleration The rate at which an object increases its velocity. Acceleration due to gravity Gravitational pull of 9.81m/s (gravity is 9.81KN/m2). Flow rate The amount of fluid that flows through a pipe at a given time. Force An influence on an object that may cause it to move (N)+. Pressure Task! This is the force per area. Look at this CWSC – both are the same size. Which is exerting the greatest pressure on the floor and can you explain why? Which is exerting the least pressure on the floor and can you explain why? CWSC 1 CWSC 2 The pressure exerted by a solid object is in a downward direction only. The pressure exerted by a liquid is not only downwards, but outwards as well. Pressure Equations! Static pressure: water is stationary Dynamic pressure: water is flowing Both are worked out the same way: Head height x 9.81(gravity) = Intensity of Pressure N/m2 Can you work these out using the formula above? What would the IoP be if the head height was 6m? 6 x 9.81= 58.86 N/m2 If the IoP was 78.48N/m2 what is the head height? 78.48 divided by 9.81 = 8M  PRESSURE, FORCE AND FLOW OF WATER Pressure: the greater the head, the greater the pressure. Kilopasca Bar Meters ls head kPa 10 0.1 1 20 0.2 2 30 0.3 3 40 0.4 4 50 0.5 5 100 1.0 10 150 1.5 15 200 2.O 20 250 2.5 25 Pressure Atmospheric pressure is exerted by the atmosphere onto every object. At sea level, atmospheric pressure is 101.3kPa; below sea level it increases and above sea level it decreases. Siphonic action happens due to atmospheric pressure; this is how many WCs flush. Pressure Siphonic action happens due to atmospheric pressure. Both cisterns have atmospheric pressure acting on them. The lower beaker has greater pressure because it is lower. When suction is applied at point C, water will flow upwards from beaker A, over the weir and down to beaker B. Atmospheric pressure is constant. The pressure at point B is below atmospheric pressure. The pressure at point A is above atmospheric pressure. B Atmospheric pressure 101.3kN/m2 A Force An influence on an object that may cause it to move. When the tap is closed the body of water is at rest. When the tap is open, the force of gravity pushes the water down the pipe and out of the tap, causing a flow of water. 1 litre of water = 1kg If the cistern holds 40 litres of water, you can work out the force of water leaving the tap. 40kg x 9.81m/s gravity = 392N Force If you reduce the pipe diameter, like on this garden hose, the speed increases and the water shoots out further, but the pressure and flow rate have reduced. Flow rate The amount of fluid that flows through a pipe at a given time. Flow rate can be affected by many factors: Changes in direction Pipe size Pressure Length of pipe Frictional resistance Constrictions. Changes in pipework If an appliance requires an increase in the flow rate, the elbows should be removed and replaced by machined bends, as this will ease the restriction. The pipe diameter can be increased, to increase the velocity of the water, which is commonly the case for a bath feed compared to a basin feed. What is the resistance of the pipework if you use elbows? What is the resistance of the pipework if you use machine bends? (This is more a factor when working with gas) Elbow 0.5m Tee 0.6m Stop valve 4.0m Check valve 2.5m Pulled bend 0.3m  In a property The incoming main CWSC and rising main to a property. First floor basin Discuss where you think the pressure is Kitchen sink the highest and why.  In a property The cold distribution, fed from the CWSC in the loft. First floor bath Discuss where you think the pressure is Ground floor the highest and why. basin CHECK YOUR KNOWLEDGE WITH THESE QUESTIONS. 1. What is this describing? The rate at which an object changes its position, taking into account speed and direction (m/s). 2. What is this describing? The amount of fluid that flows through a pipe at a given time. 3. What is dynamic pressure? 4. What is static pressure? 5. You have a CWCS in the loft, it feds a tap below. Form the cwsc the head Hight is 5m what is the intensity of pressure at the tap? Show your working out!  TRAFFIC LIGHT IT: WHERE IS YOUR LEARNING AT? Red = I have not really understood the content we have studied today (write down 2 questions that you need help with) Amber = I have understood the content on Effective Questionning (write down 1 one question you need to clarify) Green = I have understood all the content (write down one example from what we have studied)