Figure 7.26 is an illustration of a common type of water-cooled heat exchanger used in hydraulic systems.
This is typically a shell and tube-type heat exchanger. The cooling water is pumped into the heat exchanger and flows around the tube bank. The hydraulic fluid, which is to be cooled, flows through the tubes. While flowing through the tubes, the fluid gives away heat to the water, thereby reducing its temperature.
Advantages of water-cooled heat exchangers are:
1. They are very compact and cost-effective
2. They do not make noise
3. They are good in dirty environments.
Disadvantages associated with water-cooled heat exchangers are:
1. Water costs can be expensive
2. Possibility of mixing of oil and water in the event of rupture
3. Necessity for regular maintenance to clear mineral deposits.
Figure 7.25 shows an air-cooled heat exchanger.
The hydraulic fluid to be cooled is pumped through the tubes that are finned. As the fluid flows through the tubes, air is blown over them. This takes away the heat from the tubes. A fan driven by an electric motor is incorporated in the heat exchanger to provide air for cooling. The heat exchanger shown above, uses tubes which contain special devices called turbulators whose function is to mix the warmer and cooler oils for better heat transfer.
Advantages associated with air-cooled heat exchangers are:
1. Substantial cost reduction because of the use of air for cooling purposes, as compared with water
2. Lower installed costs
3. Possibility of the dissipated heat being reclaimed.
Disadvantages of air-cooled heat exchangers are:
1. Relatively larger in size
2. High noise levels
3. Higher installation costs.