Plate heat exchanger design

neqsim.process.mechanicaldesign.heatexchanger.PlateHeatExchangerDesignCalculator calculates film coefficients and overall U from plate geometry and supplied fluid properties. It reports duty, outlet temperatures, channel and port pressure losses, and frame expansion headroom. This complements the generic PLATE_AND_FRAME area estimate in HeatExchangerMechanicalDesign; it does not change that estimate or automatically select a plate exchanger for existing process equipment.

Model and units

The calculator uses the Martin 1999 friction and heat-transfer formulation. Its returned friction factor is Darcy, four times the Fanning factor in Martin’s appendix. The original transition at Re = 2000 is preserved. The correlation’s documented experimental range is Re = 200–10000; rating remains available outside it, with isWithinCorrelationRange() returning false. Chevron angles must be from 10 through 80 degrees (the heat-transfer range), measured relative to the main flow direction. Wall/bulk viscosity correction is unity.

For clear gap b, effective width W and surface enlargement factor phi:

setPortLossCoefficient specifies the combined inlet/outlet coefficient per pass; its illustrative default is 1.5. Port/manifold geometry must be checked against vendor data. Turning losses, elevation and maldistribution are excluded. sizePortDiameter(massFlow, density, maximumVelocity) gives a minimum circular port bore from a user-specified velocity limit.

All geometry is in m, developed one-face plate area in m², flow in kg/s, viscosity in Pa s, density in kg/m³, Cp in J/(kg K), conductivity in W/(m K), and inlet/outlet temperatures in °C. Pressure losses are returned in Pa; duty in W; U in W/(m² K).

The installed count includes both end plates. There are N−1 alternating fluid channels and N−2 active plates; area is (N−2) times the area of one plate. An extra channel with an even installed count belongs to the cold side. Channels must divide exactly into the specified passes on each side.

Representative glycol/seawater cooler

This example is covered by PlateHeatExchangerDesignCalculatorTest. It reproduces the thermal targets of issue #3763 within its stated 5% duty and 10% U tolerances. It is a representative rating, not an independently validated reconstruction of the vendor cooler: the issue gives no gap, width, angle, enlargement factor, plate thickness, conductivity, port diameter or fluid transport-property data. The following missing inputs are explicit engineering assumptions. They must be replaced with vendor geometry and a validated property model for equipment decisions.

Input Hot side: 40 wt% TEG/water Cold side: seawater
Mass flow, kg/h, from issue 844230 765000
Inlet temperature, °C, from issue 37 10
Assumed density, kg/m³ 1055 1025
Assumed dynamic viscosity, Pa s 0.0025 0.00108
Constant Cp, J/(kg K) 3560 4020
Assumed conductivity, W/(m K) 0.45 0.60

The heat capacities approximately close the issue’s stated duty and terminal temperatures, so that energy-balance agreement is not independent property-model validation. U is calculated from the correlations; the reference U is never an input. The example assumes clean surfaces and no wall-viscosity correction.

PlateHeatExchangerDesignCalculator calc = new PlateHeatExchangerDesignCalculator();
calc.setNumberOfPlates(721);
calc.setFrameCapacityPlates(869);
calc.setBoltedCapacityPlates(721);
calc.setPlateArea(1.49);
calc.setEffectiveFlowWidth(0.65);
calc.setPlateSpacing(0.003);
calc.setSurfaceEnlargementFactor(1.18);
calc.setChevronAngle(60.0);
calc.setPlateThickness(0.0006);
calc.setPlateConductivity(16.0);
calc.setHotPortDiameter(0.20);
calc.setColdPortDiameter(0.20);
calc.setPortLossCoefficient(1.5);
calc.setHotSide(844230.0 / 3600.0, 37.0, 1055.0, 0.0025, 3560.0, 0.45);
calc.setColdSide(765000.0 / 3600.0, 10.0, 1025.0, 0.00108, 4020.0, 0.60);

PlateHeatExchangerDesignCalculator.Rating rating = calc.calculate();
double dutyW = rating.getDuty();
double overallU = rating.getOverallU();
double hotOutletC = rating.getHotOutletTemperature();
double coldOutletC = rating.getColdOutletTemperature();
String report = calc.toJson();

Expected results (rounded): duty 17.64 MW, U 2694 W/(m² K), outlets 15.87 / 30.65 °C, active area 1071.31 m². The issue quotes 1078.5 m²; 721 × 1.49 is 1074.29 m², so its plate count, rounded individual area and total area are not exactly consistent even before excluding the two end plates. This implementation retains its explicit N−2 active-plate convention.

For the assumed 0.20 m ports, predicted losses are approximately 84 / 67 kPa. The hot port velocity is about 7.1 m/s; port loss is substantial. These are plausibility results, not a pressure-drop validation against undisclosed vendor port geometry. Increase the port diameter or use sizePortDiameter to assess an independently specified velocity limit.

Fouling and retrofit limits

The two sides independently accept existing FoulingModel instances. For example:

FoulingModel seawater = FoulingModel.createCoolingWaterModel(0.0002, 720.0);
seawater.advanceTime(720.0);
calc.setColdFoulingModel(seawater);
PlateHeatExchangerDesignCalculator.Rating fouled = calc.calculate();

Resistance is read at the model’s current operating time on every call, without advancing time or changing conditions. The overall resistance is 1/h_hot + thickness/k_metal + 1/h_cold + Rf_hot + Rf_cold. Both clean U and fouled U are reported. This represents thermal fouling resistance; it does not reduce the channel gap or predict a fouling-related hydraulic blockage. The cooling-water factory requires service-specific asymptotic resistance and time constant; it is not a calibrated seawater biofouling model.

For 721 installed plates, frame capacity 869 and bolt capacity 721:

Result Value
getFrameSparePlates() 148 plates
getFrameAdditionalArea() 220.52 m²
Active-area increase permitted by frame alone 20.58%
getAdditionalPlatesWithoutBoltReplacement() 0 plates

Capacities default to zero, meaning unknown. Unknown headroom is null in the JSON report and raises IllegalStateException through the headroom getters. An installed count exceeding either known capacity is rejected. To assess filling the frame, update the assumed bolt capacity as well as the installed count only after establishing that the retrofit is mechanically possible.

Recalculate at every new plate count: more channels lower the velocity and film coefficients. The area increase must not be used as a proportional increase in UA or duty. Bolts, tie bars, gaskets, compression length, nozzle loads and design pressure require a separate mechanical check; these capacity fields are limits supplied by the caller, not stress calculations or retrofit approval.

Process streams and limits

setHotStream(StreamInterface) and setColdStream(StreamInterface) snapshot already flashed single-phase stream properties without changing the feed. The calculator can therefore use named streams from a ProcessSystem. It does not modify their outlets or pressures. Properties are frozen at the snapshot inlet state; for large temperature changes use explicit representative mean-temperature properties through the side setters. No salinity or glycol-composition model is embedded in the calculator, and multiphase snapshots are rejected.

calculate() supports single-pass counterflow through a stable effectiveness–NTU calculation. It handles equal heat-capacity rates, tiny inlet temperature differences, equal inlet temperatures and zero flow without LMTD division. Zero flow on either side gives zero duty, unchanged outlet temperatures and zero overall conductance. Zero-flow results fall outside the correlation range. The stream adapter rejects phase change at its input; explicit property inputs require the caller to establish single-phase validity over the whole exchanger.

setHotPasses and setColdPasses support separate multipass hydraulic screening through calculateHydraulics(boolean hotSide). Multipass thermal rating is explicitly rejected: pass counts do not specify the required parallel/counterflow network, return arrangement and mixing. No silent single-pass approximation is made.

Rating and ChannelResult are immutable snapshots. Invalid subsequent inputs raise an exception; no cached old rating is returned. JSON reports label units, separate channel and port losses, and include both mechanical capacity limits.

Verification and references

Tests check independent published numerical examples for the Darcy and Nusselt correlations, both friction branches, energy conservation, port sizing and D⁻⁴ port-loss scaling, equal-capacity and zero-duty limits, fouling time ownership, plate-count changes, serialization, stream snapshots, invalid input and extrapolation reporting. The representative cooler is an assumption-based acceptance example, not an experimental validation of TEG/seawater properties.