Heat exchange Process Flowsheets & Simulations
Explore 4 validated, solved Heat exchange simulation flowsheets in MaximaLabs — real components: water, methane, ethane, propane, nitrogen. Open any one directly in your browser.
Solved via: STEAM, PENG-ROBINSON.
Hybrid cooling — a closed circuit isolated from the tower by a plate exchanger
Three loops in series, and the middle one is the point. The process is cooled by a closed circuit of treated water that never contacts air; that circuit rejects its heat across a plate exchanger into an open evaporative circuit; and only that outer circuit goes to the tower and loses water. Why a plant pays for the extra exchanger: open cooling water picks up oxygen, airborne dirt and biology, and concentrates its dissolved salts every cycle. Putting that water through a reactor jacket or a condenser is what fouls and corrodes them. The closed loop stays clean, stays at pressure, and its inventory never concentrates — so the equipment the process actually touches sees water that does not scale. Solved here: the process leaves at 318 K, the closed circuit picks that up (303 → 320 K) and is knocked back to 306 K across the plate exchanger, the open circuit takes it (301 → 311 K) and the tower returns it to 301.15 K at a 4.0 K approach to a 297.15 K wet bulb. Water loss appears only in the open circuit — the closed one leaves with exactly the flow it entered with, which is the whole claim made arithmetic. The tower also reports its scaling limit from the makeup analysis: this water saturates in calcite at 2.2 cycles, so the 4 cycles configured here shows negative headroom — a real operating conflict, left visible rather than tuned away. Bounded: steady state, so there is no basin inventory and no level control (a level is only meaningful in the dynamic engine). Fouling is not modelled — the argument for the closed loop is made by the chemistry, not by a fouling rate. Feeds and returns are open rather than recycled, the same convention cooling-water-tower uses.
10 unit ops • STEAM
22 1
View & openCooling-water utility circuit — treatment, dosing, consumers, blowdown
A whole cooling-water utility rather than a single tower: raw water is filtered, dosed, and joins a circulating header that a pump pushes through three consumers with different duties — a reactor jacket, a condenser and a compressor intercooler — before the warmed return goes to the tower and a blowdown draw-off leaves for effluent treatment. The number worth checking is the consistency between the two halves. The tower computes the blowdown it needs to hold 4 cycles of concentration (32.1 mol/s) and the makeup that implies (128.3 mol/s); the drawn blowdown split and the sized raw-water intake match those to under 1.5%. A circuit whose blowdown valve and cycles disagree is the commonest way a real plant silently runs at a different concentration than its water chemistry was designed for, and the flowsheet is arranged so you can see them agree. Solved: 300 m3/h circulating at 301.15 K, split 45/35/20 across the three exchangers, returning mixed at 312 K for an 11.0 K tower range at a 4.0 K approach. What is drawn but not modelled, stated plainly. The biocide, scale-inhibitor and corrosion-inhibitor streams are real streams carrying real flow, and their chemistry is not simulated — no inhibitor efficacy, no biological control, no corrosion rate exists in this tool. They are here because a utility flowsheet without them misrepresents the plant, not because dosing more of them will change a number. The scale risk that IS quantified comes from the tower's saturation indices against the makeup analysis, and on this water it says calcite saturates at 2.2 cycles — below the 4 being held. Blowdown leaves to a product labelled for effluent treatment; the treatment train itself is not modelled, because carrying dissolved hardness as flowsheet components requires an electrolyte package and would change the thermodynamics of the entire water loop. And there is no basin: steady state has no inventory, so a sump level and its controller belong to the dynamic engine.
26 unit ops • STEAM
27 2
View & openPressure-controlled cooling-water header
A distribution header held at pressure by a control valve, rather than a valve with a pressure typed into it. A pressure transmitter reads the header downstream of the distribution line, a controller compares it with the 4.5 bar setpoint, and its output is written back into the valve — the flowsheet is re-converged until the manipulated variable and the measurement agree. What makes it a real loop rather than a tautology is the line between them. The transmitter sits 180 m downstream, so the valve cannot simply be set to the setpoint: it has to sit above it by exactly whatever the line is losing, and the controller has to find that. Solved here, it lands at 462.1 kPa at the valve for 450.0 kPa at the header — a 12.1 kPa line loss it was never told about — in 5 control passes. The controller runs in integral mode, so the steady-state offset a proportional-only controller would leave is driven to zero: the header sits at the setpoint to the last significant figure, not near it. One detail worth copying if you build your own: the pipeline carries an explicit molar_mass. Darcy-Weisbach needs mass density and ThermoPkg.density returns mol/m³, so a line without it inflates its pressure drop by roughly 1/M — about 55x for water. It warns, but the warning is easy to miss, and 12 kPa became 587 kPa while this example was being built. Bounded: steady state, so this finds the operating point a controller settles at, not the transient getting there — no overshoot, no settling time, no derivative action. Those live in the dynamic engine. The consumer splits are fixed fractions, so this demonstrates pressure control, not flow redistribution when a user throttles.
14 unit ops • STEAM
19 0
View & openMultistream exchanger: one core, three streams, one free outlet
A cryogenic cold box is not a network of two-stream exchangers — it is one brazed-aluminium core with several streams exchanging heat simultaneously, and the multistream exchanger models it as such. Three streams share this core: 300 mol/s of 300 K feed gas being chilled, 250 mol/s of 190 K residue gas being rewarmed, and 60 mol/s of 200 K cold liquid. You specify outlet temperatures for all but one — 225 K for the feed gas, 280 K for the residue — and the remaining stream is the free one: its outlet, 230.1 K, is not specified but SOLVED, because it is what closes the adiabatic energy balance across the core. That is the correct number of degrees of freedom for an adiabatic exchanger, and specifying all three would over-specify it. The 1.08 MW duty and a composite-curve pinch check against a 3 K minimum approach come with it, so a specification that would need heat to flow the wrong way is rejected rather than reported. Bounded: this is a thermal feasibility and duty model, not a mechanical design. There is no core geometry, no layer stacking, no fin type, no per-stream pressure drop from passage dimensions — a real cold box datasheet needs all of those, and a vendor computes them from proprietary correlations.
7 unit ops • PENG-ROBINSON
10 0
View & open