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The pressure flow theory describes the movement of food through the phloem. The theory was originated by Ernst Munch.
Pressure flow refers to the movement of fluid through a conduit driven by a pressure difference between two points. This flow is governed by principles like the Hagen-Poiseuille equation for laminar flow, Bernoulli's principle for energy conservation in ideal fluids, and the Darcy-Weisbach equation for pressure loss in turbulent flow. It's fundamental in various applications, including piping systems, cardiovascular circulation, hydraulic machinery, and irrigation.
The Mass or Pressure Flow Theory, also known as the Munch Hypothesis, is a well-accepted theory that explains the mechanism of transport of organic solutes (like sugars) in the phloem of plants. This theory was proposed by a German scientist, Ernst Munch, in 1930.
The theory is based on the following key points:
Source and Sink: The 'source' is the part of the plant where the organic solutes are produced (like leaves), and the 'sink' is the part where these solutes are utilized or stored (like roots, fruits, etc.).
Active Transport: At the source, sugars are actively transported into the phloem. This process requires energy in the form of ATP. The accumulation of sugars in the phloem decreases the water potential, causing water to move into the phloem from the xylem by osmosis. This creates a high turgor pressure in the phloem at the source.
Translocation of Solutes: The high pressure at the source pushes the solutes towards the sink, where the pressure is lower. This movement of solutes from a region of high pressure to a region of low pressure is known as mass flow or pressure flow.
Utilization or Storage: At the sink, sugars are actively transported out of the phloem and utilized or stored. This decreases the sugar concentration in the phloem, causing water to move out of the phloem and back into the xylem. This reduces the turgor pressure in the phloem at the sink.
Thus, the difference in turgor pressure between the source and the sink drives the mass flow of solutes from the source to the sink. This is the essence of the Mass or Pressure Flow Theory.
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What is mean by cold chamber die casting machine?
cold chamber die casting machine can be divided into the direction of the direction of the flow of fluid in the hydraulic system used to control or regulate the pressure and flow valves, pressure valves and flow control valve three categories. A same shape as the valve, because of the different mechanisms of action have different functions. Pressure valve and flow valve with a throttle effect of the flow passage cross section to control the system pressure and flow direction valve replacement of the flow passage control the oil flow direction.
How is supersonic flow produced in a de laval nozzle?
Supersonic flow is produced in a de laval nozzle by constricting the flow in the center in order to increase the velocity. The shape will be hour-glass in nature. The initial mass flow rate and inlet pressure must be sufficient to produce a supersonic choked flow and the discharge pressure must be sufficiently low enough for supersonic flow to occur.
What is critical pressure in nozzle?
Critical pressure in a nozzle is the pressure at which the flow of material through the nozzle reaches its maximum. Beyond which any increase in pressure will not result in an increase in flow. The point at which the velocity of a fluid in the throat of the nozzle reaches the local speed of sound, creating a sonic wave, or a sonic choke.
What is the function of the impeller in a centrifugal pump?
Impeller make the flow has velocity in a centrifugal pump. The purpose of pump is increasing the pressure. The flow has velocity envergy via impeller and the energy change to pressure energy in diffuser.
What is the difference between normal flowrate and Actual flow rate?
Normal flow is 100% of the flow you actually expect. Rated flow is the maximum safety factor times the normal flow. i.e. for a maximum safety factor of 1.2 Normal flow = 100 gpm Rated flow = 1.2*100 gpm = 120 gpm Safety factors are applied to ensure a piece of equipment has some flexibility of operating conditions in its application. The minimum flow is the minimum safety factor time the normal flow i.e. i.e. for a maximum safety factor of 0.5 Normal flow = 100 gpm Rated flow = 0.5*100 gpm = 50 gpm If sized properly a pump specified in this way could operate at any point between 50 and 120gpm with no problems.
What happens to flow when pressure is increased?
Pressure decreases.
What role does pressure play in the flow of fluid?
Pressure plays a crucial role in the flow of fluid by determining the direction and speed of the flow. Fluids flow from high-pressure areas to low-pressure areas, creating a pressure difference that drives the movement. The relationship between pressure and flow rate is described by principles like Bernoulli's equation.
Does pump create pressure?
No. Pumps create flow. Resistance to flow creates pressure.
What is the impact on flow and pressure when the impeller of a pump is trimmed?
Both pressure and flow decreases
How do pressure gradients affect bulk flow?
Pressure gradients drive bulk flow by creating a difference in pressure between two points, causing the movement of fluids from high pressure to low pressure areas. The greater the pressure gradient, the faster the bulk flow of fluids will occur.
How is flow rate related to pressure?
Flow rate is directly related to pressure in a system. As pressure increases, flow rate typically increases as well. This relationship can be described by principles such as Bernoulli's equation, which shows that an increase in pressure leads to an increase in fluid velocity and thus flow rate.
Does static pressure affect flow rate?
Yes, static pressure plays a role in determining the flow rate of a fluid in a closed system. A higher static pressure typically results in a higher flow rate, while a lower static pressure results in a lower flow rate. This relationship is governed by Bernoulli's principle, which states that an increase in pressure leads to a decrease in velocity and vice versa.
What is constant flow versus constant pressure?
Constant flow means that a system delivers a consistent flow rate regardless of changes in the downstream pressure, while constant pressure means that the system maintains a set pressure level regardless of changes in the flow rate. Constant flow is commonly used in applications where flow consistency is crucial, such as chemical processing, whereas constant pressure is useful in systems where maintaining a set pressure is important, such as in water distribution systems.
What is the relationship between flow rate pressure?
With the increase in flow rate the velocity of the fluid increases. and with the increase in velocity the pressure decreases, because there will be pressure drop (Refer Bernoulli's Theorm). So with increase in Flow rate the pressure decreases.
What is pressure gradient?
It is a difference in pressure
What is a pressure differential?
its pressure between suction and discharge flow...
What area of pressure does the wind flow clockwise around?
Low pressure systems. In the Northern Hemisphere, winds flow counterclockwise around low pressure systems, while in the Southern Hemisphere, winds flow clockwise around low pressure systems.
