How it works
A heat exchanger moves thermal energy from a hot stream to a cold one through a separating wall, so the two never mix — only their energy is exchanged. The hot stream gives up sensible heat and cools; the cold stream takes it up and warms. How much heat actually crosses depends on the two streams’ heat capacities and mass flows (which side can absorb or release more energy) and on how effectively the device is arranged: a counter-current layout, where the streams flow in opposite directions, extracts far more of the available temperature difference than a co-current one, where they flow together and approach a common temperature.
The practical measure is the exchange efficiency (effectiveness) — the fraction of the maximum thermodynamically possible heat transfer that the unit actually achieves. Set it high for a good counter-current exchanger, lower for co-current or a partially fouled one. With the two inlet temperatures, the mass flows, and the heat capacities, the efficiency fixes the outlet temperatures and the duty.
The model
Dyssol Pro models the heat exchanger as a two-stream energy exchange: the two streams pass through without mixing — each outlet keeps its inlet stream’s mass and composition — and only energy crosses between them, at every time point of the flowsheet.
How much heat crosses is fixed by an exchange efficiency — the fraction of the thermodynamically maximum transfer the unit achieves — together with the two streams’ mass flows and heat capacities from the materials database. Set it high for an effective counter-current unit, lower for a co-current or partially fouled one, and the energy balance returns both outlet temperatures and the heat duty.
The efficiency stands in for the device’s geometry and flow arrangement, so on this basis Dyssol Pro covers indirect energy exchange from shell-and-tube and plate exchangers to recuperators and economizers, and whole heat-exchanger networks can be built and studied for overall energy recovery inside the flowsheet.
Equipment this model can represent
Any indirect (non-mixing) energy-exchange duty between two process streams.
Shell-and-tube exchangers
Robust, high-pressure/temperature duty; one stream in tubes, the other in the shell.
Plate / plate-and-frame exchangers
Compact, high-effectiveness, easy to clean.
Spiral and tubular exchangers
For fouling or particle-laden streams.
Recuperators / economizers
Recover heat from hot exhaust to preheat a feed.
Typical engineering studies
What teams investigate with the heat-exchanger model.
Duty & outlet temperatures
Predict outlet temperatures and heat duty for two streams at a chosen efficiency.
Heat recovery
Connect a hot dryer or kiln exhaust to a cold feed and quantify recovered energy.
Co- vs. counter-current
Compare arrangements by varying the exchange efficiency.
Heat-exchanger networks
Build and study networks for overall energy efficiency in a flowsheet.
Performance matching
Set the efficiency to match a known exchanger’s performance, then use it predictively.
Technical FAQ
How do I calculate heat duty for a solids process heat exchanger?
Heat duty is the energy crossing per unit time, fixed by the streams’ mass flows and heat capacities and the achievable temperature approach. Dyssol Pro computes it directly from the two streams’ mass flows and heat capacities and your exchange efficiency, returning the duty and both outlet temperatures.
How can I improve heat recovery in a drying or calcination process?
The standard move is to recover hot exhaust heat to preheat the incoming air or feed. In Dyssol Pro you connect the dryer or kiln exhaust to a heat exchanger against the cold feed, set the efficiency, and read off the recovered duty and the preheated-stream temperature.
Why is my heat exchanger fouling so quickly?
Rapid fouling comes from deposition, scaling, or particle build-up on the surfaces, so it is limited by higher velocities, cleanable geometries, and treating the feed. Dyssol Pro computes the duty and outlet temperatures for a given effectiveness, so a measured drop shows up as a lower effective efficiency you can study across the process.
How do I choose between direct and indirect heating?
Direct heating mixes a hot medium into the stream; indirect keeps them separate through a wall. Dyssol Pro’s heat exchanger is the indirect case (energy only, no mixing); a direct-contact arrangement would instead be modelled by mixing the streams, so the two are distinct units in the flowsheet.
How does particle deposition affect heat exchanger efficiency?
Deposits add a thermal resistance that lowers the real heat transfer, i.e. the effectiveness. In Dyssol Pro you capture that by reducing the exchange efficiency, and it computes how the duty and outlet temperatures respond.
How can I reduce steam consumption in a heat exchanger?
Steam (external heating) falls when more of the duty is met by recovered process heat. Dyssol Pro lets you add recovery exchangers and study how their efficiency and arrangement reduce the residual heating needed, trimming steam use.
What causes temperature fluctuations after a heat exchanger?
Outlet temperature swings come from fluctuating inlet temperatures or flows on either side. In a dynamic flowsheet Dyssol Pro propagates those inlet variations through the energy balance to the outlet, so you can study how upstream upsets reach the exchanger outlet.
How do I size a heat exchanger for slurry heating?
Sizing a slurry heater means finding the surface area from the required duty and a heat-transfer coefficient. Dyssol Pro computes that duty and both outlet temperatures for a target effectiveness, defining the load the area must be sized to deliver.
How can I prevent scaling in liquid heat exchangers?
Scaling grows fastest at hot surfaces with hard water and low velocity, so it is limited by keeping wall temperatures down, maintaining turbulent flow, and treating the feed. Dyssol Pro computes the stream temperatures across the exchanger, so you can favor duties that keep surface temperatures below the scaling threshold.
How can I model heat transfer between gas, liquid, and solids?
This is exactly the unit’s strength: it exchanges energy between two streams of any phase using their heat capacities and mass flows. In Dyssol Pro you connect the two streams, set the efficiency, and the energy balance gives the heat transferred and both outlet temperatures regardless of phase.
How do I optimize heat exchanger network energy efficiency?
Network optimization (pinch analysis) maximizes internal heat recovery across many exchangers. Dyssol Pro lets you build the network of heat-exchanger units in the flowsheet, set their efficiencies, and study the overall recovery to find an energy-efficient arrangement.
Why is my heat exchanger outlet temperature lower than expected?
A lower-than-expected outlet usually means the real effectiveness is below the design value — often fouling or a flow imbalance. Dyssol Pro lets you compare outlet temperatures at the assumed and a reduced efficiency, so you can infer the effectiveness the unit is actually achieving.
How does slurry viscosity affect heat exchanger design?
Viscosity lowers the real heat transfer coefficient and thus the effectiveness, and raises pressure drop. In Dyssol Pro a more viscous slurry is represented by a lower efficiency, and it computes the resulting duty and outlet temperatures so you can see the process impact.
How can I reduce fouling in a slurry heat exchanger?
Fouling is reduced by higher velocities, smoother surfaces, and cleanable geometries such as plate or spiral units. Dyssol Pro computes the duty and outlet temperatures for a given effectiveness, so you can quantify how a fouling-driven drop in efficiency plays through the process.
What causes thermal degradation in heated process streams?
Degradation happens when a sensitive stream is taken above its temperature limit. Dyssol Pro computes the outlet temperatures, so you can choose stream pairings and efficiency that deliver the required heating while keeping the sensitive stream below its degradation threshold.
How do I calculate overall heat transfer coefficient?
The overall heat transfer coefficient combines the film coefficients on each side and the wall resistance through standard correlations. Dyssol Pro computes the duty and both outlet temperatures the exchanger must deliver, which is exactly the load a coefficient-based sizing is designed to achieve.
How can I recover waste heat from dryer exhaust air?
Dryer exhaust carries recoverable sensible heat. In Dyssol Pro you connect the exhaust stream to a heat exchanger against a cold inlet (e.g. fresh drying air), set the efficiency, and quantify the recovered heat and the preheat achieved.
How do I choose between shell-and-tube and plate heat exchangers?
Plate units give higher effectiveness and easy cleaning; shell-and-tube handle higher pressures and fouling. Dyssol Pro models the energy exchange through the efficiency regardless of type, so you set the efficiency to match the candidate’s performance and compare the process outcomes.
How can I model transient heat exchanger behavior?
Real transient behavior is shaped by the wall and internals storing thermal mass, so the outlet lags and smooths a sudden inlet change. Dyssol Pro’s dynamic flowsheet re-solves the energy balance at every time step as inlet temperatures and flows change, so you can study how upstream swings propagate to the outlet temperatures.
How do I design a heat exchanger for particle-laden gas?
Particle-laden gas raises fouling and erosion concerns that drive the equipment choice, such as spiral or tubular geometries. Dyssol Pro treats the gas–solids stream’s heat capacity and mass flow and computes the duty and both outlet temperatures, so you can pin down the thermal load the design must meet.