Knowledge base
In short
In an HVAC or chilled water system a plate heat exchanger splits one large circuit into two separate ones while still passing the cooling or heat between them. It protects equipment from high pressure, keeps clean water away from dirty water and lets cold outdoor air do part of the cooling. It is chosen to divide a system, not to add capacity.
A chilled water system looks simple on a drawing: a chiller makes cold water, pumps send it round the building, coils take the cold into the air. On a real project the water often has to pass through a plate heat exchanger on the way, and the reason is rarely the cooling itself. It is the pressure, the water quality or the ownership of the pipework. This guide explains the common reasons for putting a plate exchanger into an HVAC system and what a buyer should have ready before asking for one.
Breaking The Pressure Of A Tall Building
Water in a tall building presses harder on the lowest floors than on the highest. Chillers, pumps and the lower pipework were not always made for the pressure of the whole height, and the cure is to cut the system into zones. A plate exchanger does this neatly: the plant side carries on at its own pressure, the upper zone gets a separate circuit with its own pump, and only the cooling crosses between them.
The same idea is used when an existing plant is joined to a new building, or when a part of the system is a different age and a different class of equipment from the rest.
Keeping Clean Water Apart From Dirty Water
The water on the chiller side is usually treated and clean, and the operator wants to keep it that way. The water on the building side may pass through old pipework, many fan coils and a lot of valves, and it collects dirt over the years. Without a barrier, that dirt travels back to the chiller, where it does the most harm.
With a plate exchanger in between, the dirt stays on its own side. The exchanger itself may need cleaning now and then, but that is far cheaper than a fouled chiller, and the choice between a gasketed unit that can be opened and a brazed one that cannot follows the water quality.
Cooling Without Running The Chiller
When the outdoor air is cold enough, the building does not need the chiller at all. Water cooled by an outdoor dry cooler or cooling tower can carry the load through a plate exchanger directly into the chilled water circuit. This is called free cooling, and it can take a large share of the yearly cooling duty off the chiller in a cold or mild climate. It matters most for buildings that need cooling all year, such as data centers, hospitals, laboratories and the interior of large offices.
Where a dry cooler is used in winter, the outdoor circuit carries glycol, and the exchanger is what keeps that glycol out of the building. That arrangement is described in its own guide on the plate exchanger with a dry cooler or radiator.
Heating, Heat Pumps And Heat Recovery In The Same System
Plate exchangers are just as common on the warm side. They connect a boiler or a heat pump to a heating loop, recover heat from the return air or from chillers to warm other parts of the building, and link a storage tank to the system without opening it to the building's water. In a modern building these jobs sit side by side in one plant room.
What decides the exchanger is the same set of questions each time: the liquids on both sides, the temperatures each circuit has to hold, the pressures and the room available. TECS Engineering designs and delivers plate heat exchanger solutions for engine, power plant and industrial cooling circuits; send the duty, the two circuits and the conditions on each side, and the engineering team will answer.
In Short
- Splits one system into two separate circuits
- Takes high building pressure off chillers and pumps
- Keeps dirty building water away from the chiller
- Lets outdoor cold do part of the cooling
- Links heat pumps, boilers and storage into the loop
- Gasketed where cleaning is expected, brazed where water is clean
What To Send With An Enquiry
- The duty and what the exchanger is for
- The liquids on both sides, with glycol where used
- Temperatures wanted on each side
- Operating pressures and the allowed pressure drop
- Water quality and how clean the building loop is
- Space available and whether free cooling is planned
Questions We Are Often Asked
Why put a plate heat exchanger in a chilled water system?
To divide the system into two circuits, so that pressure, water quality and ownership of each side can be handled on their own while the cooling still passes between them.
Does the exchanger add cooling capacity?
No. It passes the cooling from one circuit to the other, and a small loss of temperature is the price of the separation.
What is free cooling?
Using cold outdoor air, through a dry cooler or cooling tower and a plate exchanger, to cool the building water without running the chiller.
Gasketed or brazed in a building system?
Gasketed where the water is dirty or the unit will need opening and extending, brazed where the circuit is clean, closed and small.
What should I send to get an offer?
The duty, the liquids on both sides, the temperatures, the pressures, the water quality, the space available and whether free cooling is planned.
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.
