Zero-heat-recovery case
The dump radiator is sized for the case where the heating network takes nothing, at maximum site ambient, so the engine can keep running at full electrical output.
Application · CHP & gas engines
Dump radiators and dry coolers for CHP packages
Engine heat has to go somewhere when the heat network does not need it. We build HT dump radiators and LT-circuit dry coolers to your engine data, glycol mixture and site ambient, for packagers who want a duty-matched alternate quote.
Sized to the engine datasheetHT and LT circuits selected separately, with fan control and noise limits matched to the site.
How it works
Where the dry cooler sits in a CHP package
A gas-engine CHP unit recovers jacket-water, oil and first-stage intercooler heat through its HT circuit into the heating network. When heat demand drops (summer, weekends, network maintenance), that heat still has to be rejected if the engine is to keep producing electricity. The dump radiator, also called the emergency cooler, takes over and rejects the HT heat to air.
The LT circuit cools the second intercooler stage (mixture cooler). Its supply temperature back to the engine is low, commonly around 40–50 °C depending on the engine, and it has to hold that temperature at peak summer ambient. With only a few kelvin between fluid and air, the LT radiator is often the larger and more difficult selection of the two.
Circuits at a glance
HT and LT circuits: what sizes each cooler
| Circuit | Typical duty | What sizes the cooler | Selection notes |
|---|---|---|---|
| HT dump radiator | Jacket water, oil and HT intercooler heat; fluid roughly 70–90 °C (engine-specific) | Full HT heat with zero heat recovery, at maximum site ambient | The large temperature difference to air keeps the coil compact. Check temperature limits of gaskets, headers and fan motors in the warm discharge air. |
| LT circuit radiator | Second-stage intercooler heat; supply to the engine commonly around 40–50 °C | Small approach between LT supply temperature and design ambient | Needs more face area and airflow. Adiabatic pre-cooling is worth comparing at hot sites. |
| Single-circuit engines | Some smaller engines route all heat through one circuit | Highest-heat case at design ambient | Confirm from the engine datasheet which circuits the cooler must cover. |
Temperatures are typical ranges for orientation only. Selections are made against the engine manufacturer's datasheet for the specific model and rating.
Before we quote
What we check on every CHP selection
Glycol correction
Glycol mixtures of 30–50 % transfer less heat than water and raise pressure drop. We rate the coil with the actual mixture and flow, not a water catalogue value.
Fan control at part load
EC or speed-controlled fans hold the return temperature as heat recovery varies, and can follow a 0–10 V or Modbus signal from the CHP controller.
Noise at the boundary
CHP plants often sit near homes, hospitals and hotels. Fan speed, diameter and coil size are selected against the sound limit at a stated distance, not only the capacity.
Selection information
Send engine data for a selection
An engine datasheet plus site conditions is usually enough for a first selection. We will ask for anything that is missing. To check duty and flow first, use the sizing calculator.
- Engine model, rating and number of units
- HT and LT heat to reject at 100 % load (kW)
- Fluid and glycol concentration per circuit
- Inlet / outlet temperatures and flow per circuit
- Maximum and minimum site ambient, altitude
- Noise limit, distance and fan control signal
FAQ
CHP dry cooler questions
What is a dump radiator on a CHP unit?
It is an air-cooled emergency cooler on the engine's HT circuit. When the heating network does not take the recovered heat, the dump radiator rejects it to air so the engine can keep generating electricity without overheating.
Why is the LT circuit radiator often larger than the dump radiator?
The LT circuit must return fluid to the intercooler at a low temperature, commonly around 40–50 °C, so the temperature difference to summer air is small. A smaller temperature difference needs more coil surface and airflow for the same heat.
Can one dry cooler serve both the HT and LT circuits?
Yes, with separate coil sections in one frame, each with its own connections and temperature control. Whether that saves cost depends on the heat split, footprint and control strategy, so we can quote both options.
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