# Pressure in district heating network

• Martin V.
In summary, the figure attached shows the relation between head loss and Reynolds number in a pipe. Head loss is related to pressure difference and is affected by the velocity of the fluid, diameter of the pipe, and kinematic viscosity. The red curve represents laminar flow, while the blue curve represents turbulent flow, with the head loss increasing significantly as the Reynolds number increases. The Colebrook-White equation can be used to calculate head loss in a turbulent flow.

## Homework Statement

Can somebody explain the figure attached?

## Homework Equations

H=p/(rho*g)+(v^2/2g)+z

## The Attempt at a Solution

Search on the internet and looking in fluid mechanics book. Not possible to get book to get a explanation.

#### Attachments

• DH.png
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The figure is showing the head loss due to friction in a pipe. The vertical axis is showing the head loss (H) and the horizontal axis is showing the Reynolds number (Re). The head loss (H) is related to the pressure difference between the two ends of the pipe (dp) by the equation: H = dp/(ρ*g). The Reynolds number (Re) is a dimensionless parameter defined as: Re = vD/ν, where v is the average velocity of the fluid, D is the diameter of the pipe and ν is the kinematic viscosity of the fluid. It is used to characterize the state of the flow, whether it is laminar or turbulent. The red curve shows the head loss due to friction for a laminar flow, which is described by the Hagen-Poiseuille equation: H = 8fL/D2, where f is the Darcy-Weisbach friction factor, L is the length of the pipe and D is the diameter of the pipe. As the Reynolds number increases, the flow becomes more turbulent and the head loss due to friction increases significantly. This is modeled by the blue curve, which is the Colebrook-White equation. The head loss due to friction in a turbulent flow is highly dependent on the Reynolds number, and can be calculated using the Colebrook-White equation.

## 1. What is pressure in a district heating network?

Pressure in a district heating network refers to the force per unit area exerted by the circulating fluid (usually hot water) on the walls of the pipes in the network. This pressure is necessary to maintain the flow of hot water throughout the network and deliver heat to the consumers.

## 2. Why is pressure important in a district heating network?

Pressure is important in a district heating network because it ensures the proper flow of hot water to all connected buildings and facilities. If the pressure is too low, the water may not reach all consumers, resulting in uneven heating. On the other hand, if the pressure is too high, it can put unnecessary strain on the pipes and increase the risk of leaks or bursts.

## 3. How is pressure controlled in a district heating network?

Pressure in a district heating network is typically controlled by a pressure regulating valve, which is installed at strategic points in the network. This valve automatically adjusts the pressure to maintain a constant level, within a predetermined range, as the hot water flows through the network.

## 4. What factors can affect pressure in a district heating network?

The pressure in a district heating network can be affected by various factors, such as changes in demand for heat, the distance between the heat source and consumers, the size and condition of the pipes, and the temperature of the circulating water. In addition, any obstructions or blockages in the network can also impact the pressure.

## 5. How is pressure measured in a district heating network?

Pressure in a district heating network is typically measured using a pressure gauge, which is attached to the pipes at different points in the network. This gauge displays the pressure in units of pressure per square inch (psi) or bar. Regular monitoring of pressure is important to ensure the proper functioning of the network and to identify any potential issues that may arise.