Daily Question (February 4)

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is called friction loss. Fluid resistance is divided into frictional resistance and local resistance.

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is called friction loss. Forms of fluid flow resistance: (1) Frictional resistance. When viscous fluids flow, the frictional forces between the layers of fluid as well as the friction between the fluid and the walls of the flow channel always act to hinder the forward movement of the fluid. This type of frictional resistance that occurs along the flow path is known as frictional resistance along the flow. The portion of energy lost by a fluid due to friction along its path is known as frictional loss. (2) Local resistance: In the flow path of a fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; fluid particles collide with one another due to inertia as they move between these regions, forming vortices that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance. The energy lost by a fluid in overcoming local resistance is called local loss. Additionally, in the boiler ventilation system, it is also necessary to consider the resistance caused by the fluid scouring the tube bundle laterally. Because when the flue gas (air) flows laterally through the heated surface tube bundle, it comes into friction with the tube walls and flows around the tubes, causing vortices to form in the fluid and thus generating resistance. The resistance encountered when scouring the tube bundle in this manner is essentially a combination of frictional force and local resistance. This type of resistance should be considered separately in boiler ventilation calculations.

Flow resistance is divided into two types: laminar flow and turbulent flow. A piping system consists mainly of straight pipes and fittings. Fittings include elbows, tees, short pipes, valves, etc. Both straight pipes and fittings exert a certain resistance on the flow, resulting in a loss of mechanical energy. The mechanical energy loss caused by straight pipes is known as frictional loss in straight pipes (or head loss), and it arises due to internal friction within the fluid. The mechanical energy loss caused by fittings is called local loss, and it is primarily resulting from the fluid passing through fittings, valves, or areas where the pipe diameter suddenly increases or decreases. When applying Bernoulli’s equation, it is necessary to first calculate the values of the frictional loss in straight pipes and the local losses separately, and then add them together.

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is known as frictional loss. (1) Frictional loss: When a viscous fluid flows, the frictional forces between the layers of fluid as well as the friction between the fluid and the walls of the flow channel always act to hinder the forward movement of the fluid. This type of frictional resistance that occurs along the flow path is called frictional loss along the flow path. The portion of energy lost by the fluid due to friction along its path is known as frictional loss. (2) Local loss: In the flow path of the fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; particles in the fluid collide with each other due to inertia, vortices form, and other phenomena that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance. The energy lost by a fluid in overcoming local resistance is called local loss. Additionally, in the boiler ventilation system, it is also necessary to consider the resistance caused by the fluid scouring the tube bundle laterally. Because when the flue gas (air) flows laterally through the heated surface tube bundle, it comes into friction with the tube walls and flows around the tubes, causing vortices to form in the fluid and thus generating resistance. The resistance encountered when flushing the tube bundle in this lateral manner is essentially a combination of frictional force and local resistance

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is called friction loss.

There are two types of fluid resistance. One is the frictional resistance generated due to the viscosity of the fluid, which acts on objects in contact with it and moving relative to that fluid; this is known as frictional loss along the flow path. It is influenced by factors such as pipe length, fluid flow velocity, Reynolds number (flow regime), and pipe diameter； Another type of energy loss is caused by drastic changes in the path of flow (the trajectory) during fluid movement; this is known as local friction. Local friction occurs at turns in water pipes and at valves within them. It depends on the number of pipe fittings that cause such local losses, their friction coefficients, and the flow velocity of the fluid. Flow resistance is divided into two types: laminar flow and turbulent flow

What are flow resistance and loss? During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is called friction loss. What are the different forms of fluid flow resistance? (1) Frictional loss: When a viscous fluid flows, the internal friction between the fluid layers as well as the friction between the fluid and the walls of the flow channel always hinder the forward movement of the fluid. This type of frictional resistance that occurs along the flow path is known as frictional loss. The portion of energy lost by a fluid due to friction along its path is known as frictional loss. (2) Local resistance: In the flow path of a fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; fluid particles collide with one another due to inertia as they move between these regions, forming vortices that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance. The energy lost by a fluid in overcoming local resistance is called local loss. Additionally, in the boiler ventilation system, it is also necessary to consider the resistance caused by the fluid scouring the tube bundle laterally. Because when the flue gas (air) flows laterally through the heated surface tube bundle, it comes into friction with the tube walls and flows around the tubes, causing vortices to form in the fluid and thus generating resistance. The resistance encountered when scouring the tube bundle in this manner is essentially a combination of frictional force and local resistance. This type of resistance should be considered separately in boiler ventilation calculations.

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total amount of fluid as it moves along the flow path. This energy loss caused by flow resistance is called friction loss. (1) In the flow of viscous fluids without pressure loss, the frictional forces between fluid layers as well as the friction between the fluid and the wall surfaces of the flow channel always hinder the forward movement of the fluid. This type of frictional resistance that occurs along the flow path is known as frictional loss. The portion of energy lost by a fluid due to friction along its path is known as frictional loss. (2) Local resistance: In the flow path of a fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; fluid particles collide with one another due to inertia as they move between these regions, forming vortices that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance. The energy lost by a fluid in overcoming local resistance is called local loss. Additionally, in the boiler ventilation system, it is also necessary to consider the resistance caused by the fluid scouring the tube bundle laterally. Because when the flue gas (air) flows laterally through the heated surface tube bundle, it comes into friction with the tube walls and flows around the tubes, causing vortices to form in the fluid and thus generating resistance. The resistance encountered when scouring the tube bundle in this manner is essentially a combination of frictional force and local resistance. This type of resistance should be considered separately in boiler ventilation calculations.

During flow, the total energy of a real fluid gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total energy of the fluid as it moves through the system. This energy loss caused by flow resistance is called friction loss. Forms of fluid flow resistance: (1) Frictional loss. When viscous fluid flows, the internal friction between fluid layers as well as the friction between the fluid and the walls of the flow channel always act to hinder the forward movement of the fluid; this type of frictional resistance that occurs along the flow path is known as frictional loss. (2) Local resistance: In the flow path of a fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; particles in the fluid collide with one another due to inertia, vortices form, and other phenomena that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance. Additionally, in the boiler ventilation system, it is also necessary to consider the resistance caused by the fluid scouring the tube bundle laterally. Because when the flue gas (air) flows laterally through the heated surface tube bundle, it comes into friction with the tube walls and flows around the tubes, causing vortices to form in the fluid and thus generating resistance. The resistance encountered when scouring the tube bundle in this manner is essentially a combination of frictional force and local resistance. This type of resistance should be considered separately in boiler ventilation calculations.

What are flow resistance and friction loss? What are the different forms of fluid flow resistance? During the flow of a real fluid, its total energy gradually decreases in the direction of flow. This is because the fluid itself has viscosity, which generates internal friction forces during flow ； The flow channel boundaries cannot be completely smooth, and friction will also occur ； At the same time, during flow there are also changes in the shape of the flow channels and the direction of flow, as well as other obstacles, all of which cause resistance for the fluid as it flows. This type of resistance is called hydraulic resistance or flow resistance. Fluid flow must overcome these resistances, which causes a portion of the energy to be converted into heat energy that cannot do work and is thus lost, resulting in a gradual decrease in the total energy of the fluid as it moves through the system. This energy loss caused by flow resistance is called friction loss. Forms of fluid flow resistance: (1) Frictional loss. When viscous fluid flows, the internal friction between fluid layers as well as the friction between the fluid and the walls of the flow channel always act to hinder the forward movement of the fluid; this type of frictional resistance that occurs along the flow path is known as frictional loss. (2) Local resistance: In the flow path of a fluid, there are devices such as valves, baffles, elbows, tees, as well as sudden changes in the cross-sectional area through which the fluid flows. As the fluid flows through these localized areas, its velocity is redistributed; particles in the fluid collide with one another due to inertia, vortices form, and other phenomena that hinder the flow of the fluid. This resistance occurs in local sections, hence it is called local resistance.