NeqSim provides single-stream temperature or duty equipment and a two-stream heat exchanger. This guide separates their specifications and result APIs so that a model does not accidentally mix heater, exchanger, column-condenser, or mechanical-design semantics.

API ownership

Equipment Package Primary use
Heater neqsim.process.equipment.heatexchanger Add heat, specify an outlet temperature, or connect a heat-duty stream
Cooler neqsim.process.equipment.heatexchanger The Heater calculation with cooler naming and typically a lower outlet temperature
HeatExchanger neqsim.process.equipment.heatexchanger Exchange heat between exactly two process streams
MultiStreamHeatExchanger2 neqsim.process.equipment.heatexchanger Exchange heat among more than two streams; see the multi-stream guide
ReBoiler neqsim.process.equipment.heatexchanger Apply a specified reboiler duty to one stream
Condenser neqsim.process.equipment.distillation Model a distillation-column condenser and reflux split; it is not a two-stream exchanger

WaterCooler, air-cooler, steam-heater, and detailed shell-and-tube calculations have dedicated guides under water cooler and reboiler, air cooler, steam heater, and thermal-hydraulic design.

Runnable two-stream quick start

The following complete Java program creates independent hot and cold inlet streams, sets a UA in W/K, solves the exchanger, and checks the energy-transfer direction. getDuty() is reported in W; use Math.abs(...) when the engineering question is the transferred-duty magnitude because the sign follows the internally selected calculation side.

import neqsim.process.equipment.heatexchanger.HeatExchanger;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemInterface;
import neqsim.thermo.system.SystemSrkEos;

public final class HeatExchangerGuideExample {
  private HeatExchangerGuideExample() {}

  public static void main(String[] args) {
    SystemInterface gas = new SystemSrkEos(303.15, 30.0);
    gas.addComponent("methane", 0.90);
    gas.addComponent("ethane", 0.10);
    gas.setMixingRule("classic");

    Stream hot = new Stream("hot feed", gas);
    hot.setTemperature(100.0, "C");
    hot.setFlowRate(10000.0, "kg/hr");
    hot.run();

    Stream cold = new Stream("cold feed", gas.clone());
    cold.setTemperature(20.0, "C");
    cold.setFlowRate(8000.0, "kg/hr");
    cold.run();

    HeatExchanger exchanger = new HeatExchanger("E-100", hot, cold);
    exchanger.setUAvalue(5000.0);
    exchanger.setGuessOutTemperature(70.0, "C");
    exchanger.run();

    double hotOutletC = exchanger.getOutStream(0).getTemperature("C");
    double coldOutletC = exchanger.getOutStream(1).getTemperature("C");
    double dutyKW = Math.abs(exchanger.getDuty()) / 1000.0;
    double effectiveness = exchanger.getThermalEffectiveness();
    double minimumApproachK = exchanger.getApproachTemperature();

    if (!(hotOutletC < 100.0 && coldOutletC > 20.0 && dutyKW > 0.0)) {
      throw new IllegalStateException("Unexpected heat-exchanger result");
    }

    System.out.printf(
        "hot out %.2f C, cold out %.2f C, duty %.2f kW, effectiveness %.3f, approach %.2f K%n",
        hotOutletC, coldOutletC, dutyKW, effectiveness, minimumApproachK);
  }
}

setGuessOutTemperature(...) supplies an initial estimate; it is not an outlet specification. The two outlets retain side indices 0 and 1 from the constructor. getOutletStream() returns only side 0, so use getOutStream(int) or getOutletStreams() when both sides matter.

Single-stream heater and cooler specifications

Use setOutletTemperature(value, unit) for a unit-bearing heater or cooler temperature specification. The legacy setOutTemperature(double) accepts kelvin only and is deprecated; there is no setOutTemperature(double, String) overload on Heater or Cooler.

Other supported modes are:

The most recently selected temperature, duty, or energy-stream mode controls the calculation. After run(), read getDuty() in W or getDuty(unit) in a supported power unit such as "kW".

Two-stream exchanger specifications

UA mode

setUAvalue(double) stores UA in W/K. In this mode, give a reasonable initial outlet estimate with setGuessOutTemperature(value, unit) and solve the exchanger. Read the retained setting with getUAvalue().

For a counter-current exchanger,

\[Q=UA\Delta T_{\mathrm{lm}}\]

with

\[\Delta T_{\mathrm{lm}}=\frac{\Delta T_1-\Delta T_2}{\ln(\Delta T_1/\Delta T_2)}\]

where $\Delta T_1=T_{h,in}-T_{c,out}$ and $\Delta T_2=T_{h,out}-T_{c,in}$. The public exchanger API does not expose getLMTD() or getNTU(). getSizingReport() includes the calculated LMTD; getThermalEffectiveness() returns the solved effectiveness. The array-valued getEffectiveness() and getNtu() methods belong to FoulingScreeningResult, not to HeatExchanger itself.

Fixed outlet temperature

To pin one exchanger side, first call setOutStreamSpecificationNumber(0) or setOutStreamSpecificationNumber(1), then call setOutTemperature(value, unit). The selected side is flashed to that temperature at its inlet pressure and the other side is energy-balanced. This unit-bearing overload exists on HeatExchanger; do not confuse it with the heater API.

Results and checks

After a successful run, inspect:

Always confirm hot- and cold-side energy changes independently when using results for design or optimization. A converged process calculation is not a mechanical guarantee.

Dynamic model

The dynamic wall model is opt-in. Configure setDynamicModelEnabled(true), a positive wall mass with setWallMass(...), wall heat capacity with setWallCp(...), heat-transfer area with setHeatTransferArea(...), and shell/tube heat-transfer coefficients with setShellSideHtc(...) and setTubeSideHtc(...). Advance it with runTransient(double dt, UUID id), where dt is seconds. The no-argument runTransient() call shown in older examples is not a HeatExchanger API.

Use a ProcessSystem transient workflow when the exchanger is coupled to upstream equipment, controllers, or recycles; see dynamic simulation.

Auto-sizing and mechanical design

Call autoSize(safetyFactor) only after the exchanger has two connected streams and a solved operating point. The safety factor multiplies the absolute calculated duty. Then inspect isAutoSized() and getSizingReport().

Detailed candidate geometry belongs to HeatExchangerMechanicalDesign:

  1. Obtain it with exchanger.getMechanicalDesign().
  2. Call calcDesign() after the process-side duty and temperatures are available.
  3. Iterate getSizingResults().
  4. Read HeatExchangerSizingResult.getRequiredArea(), getRequiredUA(), getEstimatedPressureDrop(), and the other typed result getters.

There is no HeatExchangerSizingResult.getArea() method. The calculations are screening and sizing support; accountable TEMA, materials, vibration, relief, fabrication, and code compliance remain engineering-review tasks. See the mechanical-design guide, two-phase heat-transfer guide, and design framework.

Condenser and reboiler boundary

neqsim.process.equipment.distillation.Condenser is a column-tray component constructed with a name and configured through condenser/reflux APIs such as setTotalCondenser(...) and setRefluxRatio(...). It does not accept a vapor stream in its constructor and does not provide heater-style setOutTemperature(...), setDewPointTemperature(...), or setSubCooling(...) methods. Use the owning distillation-column workflow rather than treating it as a stand-alone cooler.

ReBoiler is a simpler two-port unit. setReboilerDuty(double) accepts W and adds that enthalpy to its inlet during run(); it does not perform a full column-equilibrium reboiler design.