Hydraulic systems comprise the core of industrial machines, supplying all kinds of equipment from building machines to press presses for manufacturing to the marine system and mobile machinery that is heavy duty. They generate a lot of heat when they are operating due to friction in the fluid, pressure drop, and mechanical inefficiencies. If this heat isn't efficiently controlled, the hydraulic fluid may be degraded, system efficiency may decrease, and crucial components could suffer premature wear.

This is the reason why plate heat exchangers play an essential role. The plate heat exchanger is constructed for the transfer of heat generated by hot fluids to a cooling medium, typically glycol or water, ensuring that the temperature of the hydraulic oil stays within the operational temperature.

But choosing the best plate heat exchanger to fit into a hydraulic system isn't as easy as deciding just based on its size. Many design elements need to be evaluated carefully to ensure the best efficiency in cooling, reliability, and long-term efficiency.

This article will discuss the most important design parameters to take into consideration when selecting an exchanger plate for hydraulic use.

Why temperature control matters in hydraulic systems?

Hydraulic oil serves a variety of critical essential functions:

• Transmission of power

• Lubrication of moving parts

• Transport that is contaminated

• Heat dissipation

The majority of hydraulic systems function optimally in the temperature range that is between 40°C and 60°C. When temperatures go beyond the limit, issues could arise:

1. Oil viscosity breakdown

The high temperatures decrease hydraulic oil viscosity and make it less pliable to provide the proper lubrication.

2. Oxidation and fluid degradation

Overheated temperatures accelerate the process of oxidation and lead to the formation of sludge, which reduces the lifespan of oil.

3. Seal damage

The high temperatures can cause the material to harden and break seals, leading to leaks.

4. Reduced component life

Pumps, valves, and actuators suffer from increased wear when temperatures are elevated.

A well-chosen plate heat exchanger can help keep thermal stability in check and helps avoid these problems.

Key design parameters for choosing a plate heat exchanger

1. Heat load requirement

The most important factor can be described as what is the energy load is that the exchanger needs to take away.

The term "heat load" refers to the amount of energy that has to be released from the fluid hydraulics.

It is usually measured in:

• kW (kilowatts)

• BTU/hr

• kcal/hr

How to determine heat load?

The amount of heat is based on:

• System input power

• Loss of hydraulic efficiency

• Intermittent or continuous operation

• Ambient operating conditions

A simple formula is:

Heat load = Input power x loss percentage

For instance:

If a power source hydraulic is consuming 100 kW and runs at 85 percent efficiency, that means:

Heat generated = 100 x 15% = 15 kW

The heat exchanger has to be able to remove at a minimum this amount of heat.

Why it matters

Overheating can result from undersizing.

The rate of oversizing is increasing:

• Initial investment

• Pressure drop risks

• Space requirements

Accurate heat load calculation ensures correct exchanger sizing.

2. Hydraulic fluid properties

Different hydraulic fluids do not behave in the same way.

The properties of the fluid directly impact the efficiency of heat transfer.

Important properties include:

Viscosity

Fluids with higher viscosity move more slowly and absorb heat less efficiently.

This can affect:

• Distribution of flow

• Pressure drop

• Performance of the thermal system

Specific heat capacity

This will determine how much heat the fluid is able to absorb before its temperature increases.

Density

Density can affect flow dynamics as well as the calculation of heat transfer.

Chemical composition

Certain fire-resistant or synthetic hydraulic fluids might require special materials for plates or gaskets, or compatibility.

Always provide the manufacturer of your exchanger with the complete fluid specifications.

3. Flow rate

The flow rate determines the amount of fluid that passes through the exchanger at a time.

It is typically measured in:

• Liters Per Minute (LPM)

• Gallons of water per minute (GPM)

The rate of flow affects:

• Heat transfer coefficient

• Pressure drop

• Cooling effectiveness

High flow rates

Advantages:

• Better turbulent

• Better heat transfer

Disadvantages:

• Higher pressure drop

• Greater pumping energy

Low flow rates

Advantages:

• Reduced pressure loss

Disadvantages:

• Lower heat transfer efficiency

Finding the right balance is vital.

4. Operating temperature range

Define both of the following:

Hydraulic oil Inlet temperature

The temperature at which oil enters the exchanger.

Desired outlet temperature

The temperature that is to be achieved after cooling.

For instance:

• Inlet: 75degC

• Outlet: 50degC

The exchanger has to be sized to meet the cooling requirements.

Also, think about:

• The temperature of cooling water's inlet

• Seasonal variations

• Ambient environmental conditions

The larger the difference in temperature the more efficient heat transfer will be.

5. Pressure drop limits

Pressure drop is the amount of resistance the fluid experiences while it flows into the exchanger.

Excessive pressure drop can:

• Reduce system efficiency

• Pump load to increase

• Cause cavitation

• Raise energy consumption

Hydraulic systems are especially vulnerable to losses in pressure.

If you are choosing a plate exchanger, be sure the that the pressure drop is within the acceptable limit.

Typical design considerations include:

• Plate spacing

• Plate pattern

• Geometry of flow path

• Plate number

A compact exchanger that has narrow passages can provide great cooling, but it can also cause excessive restriction.

6. Plate material selection

Material for plates should be able to work with hydraulic fluid as well as cooling medium.

Common choices can include:

Stainless steel

The best for:

• General industrial hydraulics

• Resistance to corrosion

• Long service life

Popular grades:

• SS304

• SS316

Titanium

It is used when the cooling water includes:

• Chlorides

• Saltwater

• Aggressive chemicals

Perfect for marine hydraulic systems for marine use.

Nickel alloys

It is suitable for highly corrosive environments.

The material choice affects:

• Durability

• Costs of maintenance

• Price of purchase at the beginning

7. Gasket material compatibility

In the case of heat exchangers with gaskets it is essential to select the right gasket.

The most commonly used gasket materials are:

Nitrile rubber (NBR)

It is suitable for:

• Mineral hydraulic oils

• Moderate temperatures

EPDM

It is suitable for:

• Systems based on water

• High-temperature water

Viton (FKM)

Ideal for:

• Synthetic fluids

• High temperatures

• Chemical resistance

The wrong gasket choice can result in:

• Swelling

• Leakage

• Premature failure

Always ensure that the gasket material is compatible with the chemistry of the fluid and operating temperature.

8. Plate design and corrugation pattern

The geometry of the plate can affect:

• The rate of heat transfer

• Pressure drop

• Turbulence in the flow

Common corrugation patterns are:

High theta plates

Provide:

• High Turbulence

• Better heat transfer

Also:

• Higher pressure drop

Low theta plates

Provide:

• Lower pressure drop

But:

• A decrease in thermal efficiency

The best design is contingent on your priorities for hydraulic systems.

9. Fouling tendency

Systems for hydraulics can be contaminated like:

• Varnish

• Byproducts of oxidation

• Fine particles

Cooling water could also trigger:

• Scale

• Mineral deposits

• Chemical fouling

Fouling decreases the efficiency of heat transfer.

To deal with this issue, select exchangers that include:

• Easy-clean designs

• Removable plate packs

• The proper spacing for plates

A fouling coefficient should be considered in thermal calculations.

10. Maintenance accessibility

Hydraulic systems typically operate in harsh industrial environments.

Access to maintenance is vital.

Consider:

Gasketed plate heat exchangers

Advantages:

• Easy disassembly

• Plate inspection

• Cleaning and replacement

The best option for systems that require frequent maintenance.

Brazed plate heat exchangers

Advantages:

• Compact design

• Lower cost

• Gaskets not installed

Disadvantages:

• The container cannot be opened to clean

Make your decision based on maintenance needs and the risk of contamination.

11. Installation space constraints

Space availability is often a factor in the choice of exchanger.

Plate heat exchangers have become well-known due to the fact that they provide:

• High thermal efficiency

• Compact footprint

• Flexible orientation

But, be sure to allow the additional clearance needed to:

• Removal of the plate

• Inspection

• Access to services

Always confirm the dimensions of the installation prior to making a decision.

12. Safety margin and future expansion

Hydraulic systems can suffer:

• Demand for increased production

• Higher temperatures in the air

• System upgrades

The choice of an exchanger that has 10% to 20% more thermal capacity gives you the flexibility.

This safety margin is designed to accommodate:

• Unexpected temperatures

• Aging system components

• Process modifications

Do not design your designs too close to operating limits that exceed the maximum.

Gasketed vs Brazed plate heat exchangers for hydraulics

Gasketed plate heat exchangers

Advantages

• Expandable capacity

• Serviceable

• Simple cleaning

Best for

• Large hydraulic systems for industrial use

• Poor operating conditions

Brazed plate heat exchangers

Advantages

• Compact

• Cost-effective

• High capacity for pressure

Best for

• Clean fluid systems

• Power units for compact hydraulics

Common selection mistakes to avoid

If you are choosing a plate exchanger, be sure to avoid:

Undersizing

This causes inadequate cooling.

Ignoring pressure drop

Reduce the hydraulic performance.

Overlooking fluid compatibility

Causes material degradation.

Neglecting fouling factors

Results in declining performance.

Choosing based only on cost

The lower upfront cost could make it more expensive to operate long-term.

The selection of the ideal plate heat exchanger to use in hydraulics requires an in-depth analysis of physical properties of the fluid, thermal performance and pressure limitations, as well as materials compatibility, maintenance requirements and the future demands for operation.

The most crucial design parameters comprise:

• Heating load

• Rate of flow

• Fluid properties

• The requirements for temperature

• Pressure drop

• Material for plates

• Gasket compatibility

• Resistance to fouling

• Accessibility to maintenance

A well-selected plate heat exchanger ensures:

• Stable temperature for hydraulic oil

• Longer fluid life

• System efficiency improved

• Reduced time to shut down

• Lower maintenance costs

For hydraulic professionals, the correct choice of heat exchangers is not solely about cooling. It's about protecting the system's performance and increasing efficiency over the long haul.