What Is A Heat Exchanger?

- Jul 07, 2018 -

Want to learn more about heat exchangers? What they are used for and how they work? This FAQ page is a good introduction to the subject.

1. What is a Heat Exchanger?
In short, a heat exchanger is a device that transfers heat from one medium to another, and a hydraulic oil cooler or example will remove heat from the hot oil by using cold water or air. Alternatively, the swimming pool heat exchanger uses hot water from a boiler or solar hot water circuit to heat the pool water. The heat is transferred by conduction through the exchanger materials which separate the mediums being used. Shell and tube heat exchangers passes fluid through pipes and tubes, with air cooled heat exchangers passing cold air through the fin core to cool the liquid.

2. What fluids can a Heat Exchanger operate with?
The suitability of the fluid with heat exchanger will depend on the type of heat exchanger used and the materials which are available. Standard heat exchangers are suitable for most fluids including oil, water, water glycol and sea water. For corrosive liquids such as chlorinated salt water, refrigerants and acids, other materials such as stainless steel and titanium will need to be used instead.

3. What is temperature Cross Over?
Temperature cross over is a term used to describe the scenario where the temperatures of both circuits in a liquid cooled heat exchanger begin to cross over. This can be an important factor in a heat exchanger design as the efficiency of a cooler will be significantly reduced when the temperatures cross over. In many cases a plate heat exchanger is the best option for applications where temperature cross over can't be avoided.


OilWater
Inlet Temperature8030
Outlet Temperature5051.5
Flow Rate25 L/min15 L/mi

The above table indicates that the cooling water outlet temperature is slightly higher than the oil outlet temperature. A simple way to solve this problem and increase the efficiency of the oil cooler is to increase the flow rate of the coolant. In this particular example, increasing the water flow rate to 25 L / min will reduce the water outlet temperature to 43 ° C.
 
4. What is a heat exchanger "pass" and how do I know how many passes I need?
The heat exchanger passage means that the fluid moves from one end of the heat exchanger to the other. For example, when referring to a " through tubes " circuit (usually a coolant); • Single channel - fluid enters one end of the heat exchanger and exits from the other end. • Dual Channel - A heat exchanger that enters and exists at the same end. • Triple passes - The fluid travels three times of the length of the heat exchanger body before exiting. The picture below will help to prove this;

     Single Pass (1 pass)                             Double Pass (2 pass)                        Triple Pass (3 pass)

图片.png           图片.png      图片.png


Many passes will increase the amount of heat transfer available, but will also result in high pressure loss and high velocity.
With a full suite of operating data, we can choose the most efficient heat exchanger possible whilst working within the pressure loss and velocity limits.
The number of passes on the primary circuit can also be adjusted to optimise thermal performance and efficiency by changing the baffle quantity and pitch.

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