What is a Plate Heat Exchanger?

Plate Heat Exchangers are everywhere. No matter who you are, where you are or what you do professionally, you need to reduce your energy waste. However, no home or business can afford to let their energy bills soar because the heat energy they’re paying for goes through the roof or out of the window. Heat energy loss is a big enough problem for homes. For businesses, it can be a very expensive problem. This waste of energy can place a stranglehold on their cash flow. This is why everyone from the automotive industry to heavy manufacturing uses heat exchangers to salvage as much heat as possible from waste gases. 

We see plate heat exchangers at work everywhere from fridges to air conditioning units and even in the engines of cars, ships, and planes. But what exactly are heat exchangers? How do they work? And how do you know that they’ve stopped working?

Let’s dive a little bit deeper…

What is a Plate Heat Exchanger?

A plate heat exchanger transfers heat from one fluid to another. This heat transfer takes place through a sectional division facilitated by plates. Inside you’ll find a series of plates with hollow space between them. The space between forms ducts in which the two fluids are allowed to flow, exchanging heat through the plates. As a result, plates have a larger surface area, they facilitate a faster exchange of heat than the shell and tube variety of heat exchangers.

Different exchangers use different numbers of plates depending on their heat exchange capacity. However, the more plates the heat exchanger uses, the higher the capacity in kilowatts.

This type of heat exchanger is predominantly used for liquid to liquid heat exchange. It is sometimes also used for liquid to gas heat exchange.

Many are made from conductive metals. However, they can also be made with ceramics, plastic polymers and metal or ceramic composites. 

Manufacturers of plate heat exchangers include Alfa Laval, APV/SPX, GEA and Schmidt Bretten.

The composition of a Plate Heat Exchanger (How it works)

Let’s take a closer look at how a Plate Heat Exchanger is put together. The exchanger is built upon a frame with one fixed heavy section to the front and rear. This has a number of ports (usually four) and a heavy moveable section that slides along a guiding bar. A series of clamping bolts run down the side of both heavy front and rear plates and the interior plates are placed and clamped between them.

Each plate has a gasket, allowing the plates to form a closed system of flow channels. This allows both the primary and secondary fluids to flow through every other plate. The gaskets are either clipped or glued onto the plates, separating the different media (liquids and/or gases) on the primary and secondary circuits.

Gaskets are fitted to the front and rear plates in the heat exchanger around all four ports. The plates in between, however, have a gasket around two ports controlling which plate circuit the fluid is allowed to flow through.

Flow diagram | Heat Exchanger Parts | WCRUK
The composition of a Plate Heat Exchanger

How do I know if my Plate Heat Exchanger isn’t working?

Now that we know a little about what a plate heat exchanger is and how it works, let’s take a look at some of the signs that yours may be in need of repair or replacement.  However, the sooner you recognise the signs of a malfunctioning plate heat exchanger, the better your chances of mitigating any loss of energy efficiency. 

Keep an eye out for the following warning signs;

Abnormal/poor performance

Poor performance is the most common issue with Plate Heat Exchangers. If you notice that yours is performing erratically or less effectively than usual this could be due to a number of factors. Poor performance is usually attributed to;

  • An error in the plating
  • An accumulation of dust, dirt or debris within the unit (this is known as fouling)
  • A buildup of mineral deposits on the plates (known as scaling) 
  • Something impeding the flow of liquid
  • A faulty installation.

Try running a standard CIP cycle to clear out any excess matter in the heat exchanger. If the debris does not clear, you may need to clean the unit manually. 

Leaks

If you notice deposits of liquid outside the plate heat exchanger, fast intervention is needed. Most commonly, a leak indicates that the gaskets have been damaged, although it can also be a sign of improper assembly. Unless proper aligned at the top and bottom, the plates can move from side to side or up and down during the tightening process. This causes the gaskets to become misaligned resulting in leakage.

Liquids mixing

If the liquids inside the unit begin to mix together, this indicates that the plates are leaking within the unit. The most likely explanation for this is that the unit has been damaged and one of the plates has become perforated.

A simple pressure test should be all you need to confirm this. All you need to do is fill the unit with water but only pressurise one side. If there is a perforated plate, the side which has not been pressurized will start to overflow. 

Apply constant water pressure to one side of the unit. You should never use compressed air with a plate heat exchanger. Fill the other side of the unit with water, but do not continue pressure on this side. Open the connections on the side which has not been pressurised. A plate that is perforated on the pressurised side will leak into the unpressurised side causing an overflow. 

If a plate is found to be perforated, you will need to disassemble the unit and inspect the plates with a crevice detection liquid. 

Can I repair my Plate Heat Exchanger myself?

Even the slightest misalignment of the plates or the plates being put back in the wrong order can cause catastrophic failures. In short, unless you’re absolutely certain of what you’re doing, attempting to repair a plate heat exchanger yourself can create more problems than it solves. 

Plate heat exchangers can be extremely difficult to put back together unless you know you’re inserting the plates in the right order, which is why it’s vital to number them as you go.

It’s highly recommended that you consult a professional to inspect and repair your plate heat exchanger. If it cannot be repaired it will need to be replaced… But this is still much more cost effective than simply going without one!

If you have a question regarding service or repair of your plate heat exchanger contact us to see how we can help.