Are you seeking to achieve peak performance in your industrial pipeline design? At Manuflo, we understand the importance of crafting a robust engineering scheme that perfectly aligns with your production needs. Today, we’ll delve into the crucial aspects of determining flow velocity (V), pressure (P), and flow rate (Q) in your pipeline to help you make informed decisions.

Understanding the Relationship of Pressure, Velocity, and Flow Rate in Pipeline

The relationship between flow velocity (V), pressure (P), and flow rate (Q) is the foundation of efficient pipeline design. Let’s take a practical example to illustrate the connection between these three vital factors.

Consider a pipe size with dimensions φ25.4×1.65, and the medium being nitrogen gas. The working pressure (P) is 0.8MPa, and the operating temperature (t) is 20℃. Now, the question arises – how do we find the flow rate (Q) under these specific working conditions?

Calculating Flow Rate: A Step-by-Step Guide

To calculate the flow rate (Q) of the medium flowing through the pipeline per hour, we use the following formula:

Q = V * π * R^2 * 3600


Q: Volume flow (m³)

V: Medium velocity (m/s)

R: Pipe radius (m)

Choosing the Right Flow Velocity

In real-world applications, the flow velocity (V) is influenced by several factors, including operating pressure, pipeline diameter, and gas usage. To ensure an optimal pipeline design, it’s essential to determine a reasonable flow velocity.

A typical velocity range for liquid measurements is 0.5~3m/s, while for gas flow rates, it’s 10~30m/s. Considering an operating pressure of 0.8Mpa, we recommend selecting a velocity (V) of 10m/s, assuming an inner pipe diameter of 22.1mm.

Converting to Standard Flow

Finding common standard conditions for metering flow rates is essential when dealing with various operating pressures. For this purpose, we utilise the Ideal Gas Law (PV = nRT) to calculate flow rates under normal conditions.

P—gas absolute pressure KPa
V—gas volume m3
n—the amount of substance in the gas kmol
R—gas molar constant 8.314kj/(kmol .K)
T is the thermodynamic temperature K of the gas

The Difference Between Standard Condition and Working Condition

Before we move forward, it’s crucial to understand the distinction between standard conditions and working condition flow rates. While the units remain the same, the corresponding flows differ. We use the temperature of 20°C (293K) and the atmospheric pressure of 101.325kPa (1 standard atmospheric pressure) for everyday conditions.

Selecting the Right Flow Meter for Measurement

Now that we’ve covered the basics of calculating pressure, velocity, and flow in pipeline design, let’s explore how to choose the perfect flow meter for your needs.

Example: Determining Flowmeter Specifications

Suppose the actual working pressure of a gas supply pipeline ranges from 0.8MPa to 1.2MPa (gauge pressure). The medium temperature fluctuates between -5℃ to 40℃, and the gas supply volume falls within 3000~10000Nm³/h (standard flow rate). Without considering the composition of natural gas, we must determine the flowmeter’s specification and model.

By applying the gas equation (Qb = Q * PTb / PbT * Zb / Zg = Q * C * F2), we calculate the flow range required for the flowmeter, which lies between (214-1200) m³/h.

Based on this flow range, we recommend selecting a flowmeter that aligns perfectly with your working conditions.

At Manuflo, we pride ourselves on offering high-quality flowmeter solutions designed to optimize your pipeline performance. Contact us today to explore the suitable flowmeter options for your industrial needs.

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