Protection of external pipelines

Pipe Fluid Freezing Time Calculator

Rating for a still liquid in a horizontal or vertical area outdoors.The calculation separates cooling to the crystallization point and subsequent freezing with the growth of the ice layer.

natural convection wind blowing thermal radiation

Liquid: water
Pipe: steel
Insulation: 50 mm

Design scheme

Pipe position

Horizontal Vertical

For free convection, horizontal cylinder correlation is used.

Geometry

Pipe and section

Pipe outer diameter mm Wall thickness mm Open length m

Ends and fittings are not taken into account.For a vertical pipe, the length also determines the characteristic size of natural convection.

Terms

Liquid and air

Initial temperature °C Air temperature °C Wind speed across the pipe m/s

At zero speed, only free convection is taken into account.The wind is assumed to be directed across the axis of the pipe.

Thermal protection

Thermal insulation

Material Insulation thickness mm Thermal conductivity λ W/(mK)

Calculated value λ = 0.040 W/(m K).For the project, use the manufacturer’s value at operating temperature.

Pipe and fluid properties Water and carbon steel are selected by default

Liquid

Liquid type

Crystallization temperature °C Density kg/m³ Heat capacity J/(kg K) Latent heat kJ/kg Thermal conductivity of the solid phase W/(mK)

For glycol solutions, specify the manufacturer’s data.Their freezing occurs over a range of temperatures, so the one-point model will be approximate.

Pipe and outer surface

Pipe material

Thermal conductivity of the pipe W/(mK) Pipe density kg/m³ Heat capacity of the pipe J/(kg K) Shell blackness degree ε

ε ≈ 0.9 for a painted or non-metallic surface;0.05–0.2 for pure aluminum casing.

The calculation is performed for constant air temperature and stationary liquid.

Result

Time before freezing

—

First crystals — cooling to freezing point

Complete freezing — from initial temperature

Crystallization stage — taking into account the growing layer of ice

Heat loss at the beginning of freezing — —

Start —

First crystals —

Complete freezing —

Temperature profile

Temperature change over time

In the crystallization area, the temperature is constant, and the proportion of ice increases from 0 to 100%.

Beginning of crystallization: — Complete freezing: —

Inner diameter —

Liquid mass —

Outer diameter of insulation —

Heat transfer coefficient —

Surface temperature —

Linear heat transfer coefficient —

Show calculation model

Limits of applicability

What is important to consider at the site

Liquid is motionless

Circulation, make-up and internal heat sources are not taken into account.Even a small constant flow can significantly increase the time.

The weather is constant

Temperature and wind do not change.Sun, clear sky cooling, precipitation, snow and wet insulation are not included in the model.

This is an engineering estimate

Cold bridges on supports, reinforcement and joints can determine the real moment of freezing before the straight section.

Methodology and sources of initial data

The cylindrical thermal conductivity of the pipe and insulation is calculated from the logarithmic resistance of the layer.
Natural convection—Churchill-Chu correlations for a horizontal cylinder and a vertical surface.
Wind blowing - Churchill-Bernstein correlation for a cylinder in a cross-flow.
Complete freezing is calculated step by step by the balance of latent heat with the resistance of the growing annular layer of ice.
ASHRAE Handbook: Thermal Insulation of Utility Systems.
NIST: natural convection near a horizontal cylinder.
Churchill & Bernstein: cross flow cylinder.