An air-blast cooler is a heat exchanger that limits the temperature of a transport fluid, such as oil, by dissipating its heat into the surrounding air. Selecting the appropriate air blast cooler for your hydraulic system is essential for protecting system components, improving oil longevity, and maintaining overall system efficiency. Whether you’re specifying a heat exchanger for industrial machinery, marine applications, or mobile plant, it’s critical to match your cooler to your system’s heat load, airflow conditions, and operational environment.
At MacScott Bond, we proudly supply AKG and Emmegi air blast coolers for your hydraulic system, two globally respected manufacturers of heat exchangers known for their reliable, high-performance designs. In this brief guide, we’ll walk through the key considerations in selecting the right air blast cooler for your application.
The Role of Hydraulic Oil in Heat Transfer
In a hydraulic system, heat is an unavoidable by-product of operation. It is primarily generated by inefficiencies such as mechanical friction in pumps, motors, and actuators, as well as fluid resistance as the oil flows through manifolds, pipes, and valves. As the hydraulic oil circulates, it absorbs heat from these hot components. Thanks to its excellent thermal transfer properties, the oil can pick up this heat efficiently and carry it away.
The heated oil then travels through the hydraulic circuit to a central cooler, where the heat can be managed. Inside the cooler, the fluid passes through a heat exchanger (such as an air-blast cooler) where it releases the absorbed heat into the fan-driven air. This process cools the oil back down to its optimal operating temperature before it returns to the reservoir or pump inlet to continue the cycle. Meanwhile, the warmed air is dispersed and mixed with the surrounding ambient air.
Understanding Heat Load and Oil Flow
The most critical factor when choosing an oil cooler is the heat dissipation requirement, typically expressed in kilowatts (kW). This is the rate of thermal energy the cooler must remove to ensure the hydraulic oil is always within an acceptable operating temperature limit.
Example of Specific Heat Rejection Air Blast Cooler Chart
To calculate heat load, you’ll need:
- Hydraulic input power (kW)
- System efficiency (usually ~80 - 85%)
Once you know your heat load, you can refer to cooling performance charts provided by manufacturers such as AKG or Emmegi. These graphs show cooling capacity (kW) based on oil flow rates and temperature differentials.
To read cooling capacity, you’ll need:
- Hydraulic flow rate (L/m)
- Ambient air temperature (°C)
- Desired oil temperature drop
For example, if you have an oil flow of 60 L/min and want to reduce the oil temperature from 70 °C down to 50 °C in a 30 °C ambient environment, you’ll use this data to determine the cooler size required.
Airflow and Fan Types
Air-cooled heat exchangers use a fan-blown flow of ambient air to remove heat from the hydraulic oil as it passes through the finned tubes of a radiator-like convection core. The airflow volume and fan design significantly affect performance, with different cooling fan types available for high-performance or high-debris environments. The fan is driven by a motor.
Flexible motor options include:
| Motor | Applications |
| Electric (AC) | Ideal for stationary installations with a continuous power supply (3-phase, heavy-duty variants are also available) |
| Electric (DC) | 12/24V, Suitable for mobile and vehicle-based systems |
| Hydraulic | Often used in heavy-duty industrial or off-road settings |
It's important to assess whether your installation site has adequate ventilation to allow cooling air to enter the heat exchanger and the warm air to exit and dissipate. Restricted airflow can significantly reduce the cooler’s effectiveness. In such cases, larger fans or a repositioning of the cooler may be required.
Managing Noise and Environmental Conditions
Fan-driven coolers generate varying degrees of noise. If your installation is in a noise-sensitive area, low-noise fan models (available from both AKG and Emmegi) can help meet local or on-site regulations.
Environmental factors like dust, vibration, and exposure to corrosive agents must also be considered. For example, offshore applications may require corrosion-resistant coatings, while mobile plants may need antivibration mounts.
Additionally, for systems with automatic cooler control, thermostat placement and configuration are crucial. One frequent issue we see is incorrect thermostat temperature set points, leading to the cooler cycling rapidly between running and idle. Always ensure the switch-off temperature is set much lower than the switch-on temperature to avoid constant on-off cycling that leads to premature fan and motor wear and more fan noise disturbance.
Air Blast Coolers from MacScott Bond
At MacScott Bond, we use cooling performance graphs alongside your system’s duty cycle, oil type, and ambient conditions to specify the ideal oil cooler. Whether you're working with hydraulic oil, coolant, transmission fluid, or other media, we’ll help you select the best-fit unit from leading suppliers like AKG and Emmegi.
