Types of Heat Exchanger

 

 

Shell and Tube type

 

 

The shell side is shown as silver coloured flanges, the tube side being red.

The shell side usually contains the process fluid and the tube side water from the town mains or a cooling tower, or an ethylene glycol solution from a chiller unit.

 

Stainless Steel Heat Exchangers are particularly useful in bad water environments caused by pollution or from the chemicals used to counter it. They can also be used to overcome the corrosive nature of some synthetic oils and refrigerants.

 

Plate type

 

The heat transfer surface consists of a number of thin corrugated plates pressed out of a high grade metal.

The most common plate material is stainless steel.

Plate and frame heat exchangers were first used in the food and dairy industries, where the ability to access plate surfaces for cleaning is imperative.

The heat transfer surface consists of a number of thin corrugated plates pressed out of a high grade metal.

The pressed pattern on each plate surface induces turbulence and minimises stagnant areas and fouling.

 

The diagram below shows a honeycomb arrangement of heat exchanger plates.

 

 

The pressed pattern on each plate surface induces turbulence and minimises stagnant areas and fouling.

Unlike shell and tube heat exchangers, which can be custom-built to meet almost any capacity and operating conditions, the plates for plate and frame heat exchangers are mass-produced using expensive dies and presses. Therefore, all plate and frame heat exchangers are made with what may appear to be a limited range of plate designs.

 

The inlet and outlet connections in the plate heat exchangers shown above are axially in line. This means that they can be installed directly in pipework without any change of direction. Each fluid stream flows in series through alternate plates. As a consequence, the plate spacing is larger and internal velocities are higher than is normally the case with this type of heat exchanger, thus rendering them less prone to fouling.

The units sown above feature stainless steel AISI 304 / 316 plates and EPDM (Ethylene Propylene Diene Monomer sometimes called Ethylene Propylene rubber).

gaskets. The gaskets are arranged so that the two media are directed into the alternate channels created by the plates. A double seal arrangement around the two ports ensures that if fluid leaks it passes through the interspace direct into the atmosphere, avoiding cross contamination.

The plate pack consists of a number of herringbone patterned, pressed heat transfer plates. These are assembled in an inverse formation to create two sets of parallel channels, one for each liquid. Since the herringbone patterns point in opposite directions a large number of points of support are achieved, creating a lattice in each channel. This provides a high level of turbulence, which in turn leads to an elevated rate of heat transfer.

 

Plate Heat exchangers have the following uses; heating and cooling for the brewing, food, dairy, pharmaceutical and power generation industries; heat recovery for the chemical, pharmaceutical, power generation and paper & pulp industries.

 

In Line Plate Heat Exchanger

 

In Line Plate Heat Exchangers have been designed as a low-cost alternative to shell and tube types.

They consist of numerous 316 stainless steel heat transfer plates, two outer covers and four connections copper vacuum-brazed together to form an integral unit.

 

Gaskets

 

Gasket properties have a critical bearing on the capabilities of a plate and frame heat exchanger, in terms of its tolerance to temperature and pressure.

Gaskets are commonly made of:

Nitrile rubber.

Hypalon.

Viton.

Neoprene.

EPDM (Ethylene Propylene Diene Monomer).

 

 

 

Plate type for Hot Water Heating


The plate heat exchanger shown below is used to generate hot water cutting out storage altogether.

This reduces the risk of the legionella bacteria.

Also the Hot Water system can be easily pressurised from the supply mains water system.

The packaged Hot Water heat exchanger shown above is fitted with primary pumps and a 4-port motorised primary control valve together with a built in bypass. The control box is fitted with a PID temperature controller.

Combined type

The unit shown above is a semi-instantaneous hot water system comprising a DHW instantaneous compact plate heat exchanger with a combined storage vessel.

This hot water heater has been designed to enable a reduction in the necessary boiler power rating and storage volume without a corresponding decrease in the amount of hot water capable of being delivered.

 

 

The Hot Water Storage Cylinder is sized to deliver small Hot Water flows in the building.

When a larger amount of Hot Water is required then the Plate Heat Exchanger can deliver the appropriate amount instantaneously.

The Secondary Return Water is heated by the Plate Heat Exchanger where it passes into the Storage Cylinder until it is required.

Another way to operate this system is to reduce boiler power and make the Hot Water Cylinder large enough to cope with a significant portion of the Hot Water demand.

The storage vessel shown above would have to be capable of being pressurised so that enough pressure is available at outlets.