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| Heat Exchangers
Heat Exchangers & Design
Heat exchangers are devices which permit an exchange of heat between two moving fluids at different temperatures. The two fluids are generally separated by a solid surface which is almost always of metal. Heat exchangers can be divided into three groups on the basis of the motion of the two fluids inside the device:
- Parallel current heat exchanger, when the two fluids move in parallel in the same direction at all points of the exchanger;
- Countercurrent heat exchangers, where the two fluids move in parallel but in opposite directions;
- Crosscurrent heat exchangers, where the two fluids move at right-angles to each other.
The design of a heat exchanger is intended to calculate the required exchange surface which is a function of the quality of heat to be transmitted, of the temperatures and the oil flow rates of the two fluids.
Water-Oil Heat Exchangers for Hydraulic Systems
The water-oil heat exchangers which are normally used in hydraulic systems generally consist of a tube nest, made up of several tubes with water circulating inside and oil circulating outside the tubes. The group is installed into another container called the shell. The oil is driven over the whole exchange surface area since its flow is formed by baffles to follow a pre-set path through the exchanger. |
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Water-Oil Heat Exchanger
with Tube & Bundle |
Water-Oil Heat Exchanger
with Brazed Plates |
Air-Oil Heat Exchangers for Hydraulic Systems
The use of air for cooling hydraulic systems is becoming more and more common, due to;
- Lack of water;
- The system is not connected to water mains;
- The operating costs are lower than water-oil exchangers;
- The hot air which emerges can be used for room heating during the winter.
Since air is a poor heat conductor, very large exchange surfaces are required to disperse the heat. The most modern air-oil heat exchangers are in aluminum since this has proved to be the most suitable material in terms of conductivity and its other specific characteristics. These heat exchangers are made up of superimposed aluminum pressed strips, shaped to create sections in which air and the oil circulate. Turbolators are used in the oil ducts in order to achieve higher thermal efficiency.
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Air-Oil Heat Exchanger
with Alternating Current Electric Fan |
Air-Oil Heat Exchanger
-Series AP with Hydraulic Motor |
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