Knowledge base
An engine turns only part of its fuel into electricity; the rest leaves as heat in the cooling water, the oil, the charge air and the exhaust. A combined heat and power plant collects that heat and sells it as hot water, and the plate heat exchanger is the part that hands it over from the engine to the heating circuit. This guide explains where the exchanger sits in the heat recovery chain, why a plate exchanger is used there and what it has to cope with.
The Handover Point
The engine's cooling circuits are closed and belong to the engine: a treated mixture, a set pressure, a flow the engine maker asks for. The heating circuit belongs to the customer: a district network, a building, a greenhouse or a process, with its own water, its own pressure and its own pumps. A plate heat exchanger stands between them. The engine's heat crosses the plates and the heating water carries it away, but the two liquids never meet, so a problem in the network cannot reach the engine and the engine circuit cannot leak into the network.
Collecting Heat Along The Chain
Heat recovery is usually arranged as a chain. The heating water passes first through the exchangers that collect the lower-grade heat, such as the oil and the charge air where they are recovered, then through the exchanger on the jacket water circuit, and finally through the exhaust heat exchanger, which raises it further. The exhaust exchanger is a separate unit built for hot gas, because a plate exchanger is not meant for exhaust; the plate units do the liquid-to-liquid work before it. The order matters, and it is set so that each source gives up as much heat as it can.
Why A Plate Exchanger Is Used
Engine plants are often built as compact containers or skids, and a plate exchanger delivers the duty in little space. It can bring the heating water close to the temperature of the engine circuit, which means more heat sold from the same engine. It reacts quickly when the engine load or the heat demand changes. The gasketed kind can be opened and cleaned when the heating side, which is often the less clean of the two, leaves deposits; the brazed kind suits smaller plants with clean, closed circuits.
When Nobody Wants The Heat
Heat demand rarely matches the engine exactly: a warm day, a network fault or a stopped process can leave the heating side unable to take the heat. The engine must still be cooled, so the plant needs a second way out, usually an emergency cooler or dump radiator, and a control valve that sends the engine heat to the exchanger or to the radiator as needed. The plate exchanger and the radiator are designed together so that the engine stays within its limits in both cases. TECS Engineering designs and delivers plate heat exchanger solutions for engine, power plant and industrial cooling circuits, and builds the radiators and emergency coolers that go with them; send the engine data, the heat demand and the site conditions and the engineering team will answer.
In Short
- Hands the engine's heat to the heating circuit while the liquids stay apart
- Protects the engine circuit from the heating network and the network from the engine
- Part of a chain: oil and charge air, then jacket water, then exhaust
- The exhaust heat exchanger is a separate unit built for hot gas
- Compact, close in temperature and quick to react
- An emergency cooler takes the heat when the heating side cannot
What To Send With An Enquiry
- Engine data sheet with the heat of each circuit
- The heating circuit: its water, temperatures and flow
- Which heat sources are to be recovered
- Pressure on each side and the allowed pressure drop
- How the heat demand varies and what happens when it stops
- Space available, site conditions and any material specification
Questions We Are Often Asked
What does a plate heat exchanger do in a CHP plant?
It passes the heat of the engine's cooling circuits to the hot-water circuit that delivers it to the customer, while keeping the two liquids apart.
Can a plate heat exchanger recover exhaust heat?
Not directly. Exhaust heat is collected by a separate exchanger built for hot gas; the plate exchangers handle the liquid circuits before it.
Why not connect the engine straight to the heating network?
The network's water, pressure and cleanliness are not what the engine needs, and a fault on one side would reach the other. The exchanger keeps them separate.
What happens when the heat is not needed?
A control valve sends the engine heat to an emergency cooler or dump radiator, so the engine stays cooled whatever the heating side does.
Which type of plate exchanger is used?
A gasketed unit where the heating side may foul and cleaning access is wanted; a brazed unit in smaller plants with clean, closed circuits.
Contact Us
Send us the heat duty, the fluid temperatures and flow rates, the ambient conditions and the installation limits. We answer with a design proposal - or write to us on WhatsApp.
