NeqSim represents a pipe wall as concentric material layers and can combine their cylindrical conduction resistance with a simplified surrounding-environment model. Use this page for screening and for preparing heat-transfer inputs. It does not replace a hydraulic flow model, a transient thermal model, or a qualified insulation design.

Model basis

For a layer with inner radius $r_i$, outer radius $r_o$, thermal conductivity $k$, and unit pipe length, NeqSim uses

\[R'_{layer} = \frac{\ln(r_o/r_i)}{2\pi k}\]

where $R’$ is in K m/W. PipeWall.calcCylindricalThermalResistancePerLength() sums this resistance over all layers. PipeWallBuilder.calcOverallUValue(double) adds the inner-film and outer-environment resistances and returns an overall coefficient in W/(m² K), referenced to the inner pipe area.

The builder’s inner-film argument is caller-owned. NeqSim does not infer it from a flow regime in this geometry calculation. The air, seawater, and soil environment factories also use simplified correlations; verify their applicability for the actual installation.

Units and current API

Quantity Unit Current API
Inner diameter, radius, layer thickness m PipeWallBuilder, MaterialLayer, PipeWall
Material conductivity W/(m K) PipeMaterial.getThermalConductivity()
Density kg/m³ PipeMaterial.getDensity()
Specific heat capacity J/(kg K) PipeMaterial.getSpecificHeatCapacity()
Ambient temperature K exposedToAir, subseaEnvironment, buriedInSoil
Wind or current velocity m/s environment factory argument
Inner-film coefficient W/(m² K) calcOverallUValue(double)
Resistance per unit length K m/W calcCylindricalThermalResistancePerLength()

PipeWallBuilder has a private constructor. Start with a factory such as carbonSteelPipe, barePipe, withInnerDiameter, or subseaPipe. Add layers from the inside out. The predefined PipeMaterial values are nominal properties near 20 °C, not temperature-dependent material certificates.

Executable subsea screening example

This complete Java 8 program builds carbon steel, FBE, and polyurethane layers. It adds a simplified seawater environment, evaluates the overall coefficient, and calculates a screening heat loss per metre from bulk-fluid to ambient temperature.

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import neqsim.fluidmechanics.geometrydefinitions.internalgeometry.wall.PipeMaterial;
import neqsim.fluidmechanics.geometrydefinitions.internalgeometry.wall.PipeWall;
import neqsim.fluidmechanics.geometrydefinitions.internalgeometry.wall.PipeWallBuilder;
import neqsim.fluidmechanics.geometrydefinitions.surrounding.PipeSurroundingEnvironment;

public final class PipeWallHeatTransferGuideExample {
  private static final Logger LOGGER =
      LogManager.getLogger(PipeWallHeatTransferGuideExample.class);

  private PipeWallHeatTransferGuideExample() {}

  public static void main(String[] args) {
    double innerDiameterM = 0.254;
    double steelThicknessM = 0.0127;
    double fbeThicknessM = 0.0004;
    double insulationThicknessM = 0.050;
    double bulkFluidTemperatureK = 333.15;
    double seawaterTemperatureK = 277.15;
    double seawaterCurrentMPerS = 0.5;
    double innerFilmCoefficientWPerM2K = 800.0;

    PipeWallBuilder builder =
        PipeWallBuilder.carbonSteelPipe(innerDiameterM, steelThicknessM)
            .addFBECoating(fbeThicknessM)
            .addInsulation(PipeMaterial.POLYURETHANE_FOAM, insulationThicknessM)
            .subseaEnvironment(seawaterTemperatureK, seawaterCurrentMPerS);

    PipeWall wall = builder.build();
    PipeSurroundingEnvironment environment = builder.buildEnvironment();
    double resistanceKMW = wall.calcCylindricalThermalResistancePerLength();
    double overallUWPerM2K = builder.calcOverallUValue(innerFilmCoefficientWPerM2K);
    double heatLossWPerM =
        overallUWPerM2K
            * 2.0
            * Math.PI
            * wall.getInnerRadius()
            * (bulkFluidTemperatureK - seawaterTemperatureK);

    assert wall.getNumberOfLayers() == 3;
    assert environment.isSubsea();
    assert resistanceKMW > 0.0;
    assert overallUWPerM2K > 0.0;
    assert overallUWPerM2K < innerFilmCoefficientWPerM2K;
    assert heatLossWPerM > 0.0;

    LOGGER.info(
        "layers={}, outerDiameter={} m, resistance={} K m/W, U={} W/(m2 K), heatLoss={} W/m",
        wall.getNumberOfLayers(),
        2.0 * wall.getOuterRadius(),
        resistanceKMW,
        overallUWPerM2K,
        heatLossWPerM);
  }
}

Run the program with assertions enabled (java -ea ...). The assertions are executable checks, not design acceptance criteria.

Environment choices

For a custom material, use addCustomLayer(name, thicknessM, conductivityWPerMK, densityKgPerM3, specificHeatJPerKgK). The thickness is the second argument; older examples that put conductivity second are incorrect.

Flow-solver integration boundary

PipeWallBuilder is a geometry screening API. It does not automatically configure a OnePhasePipeLine. The Pipeline API uses the plural array setters setOuterTemperatures(double[]), setPipeOuterHeatTransferCoefficients(double[]), and setPipeWallHeatTransferCoefficients(double[]). Each array must contain numberOfLegs + 1 values, representing the boundary values along the legs. There is no singular setOuterTemperature(double) or setOverallHeatTransferCoefficient(double) on this pipeline type.

Do not insert the builder’s overall coefficient into a wall-film or outer-film array without reconciling the resistance basis. For a correlation-based pipeline model, follow the model-specific heat-transfer contract in the pipeline simulation guide.

Engineering limits

For a local bare-pipe outdoor surface-temperature calculation, see the heat-transfer guide.