To put it simply, a heat exchanger is a device that transfers heat from one medium to another. A hydraulic oil cooler, for instance, will remove heat from hot oil by utilising cold water or air.
As an alternative, a swimming pool heat exchanger warms the pool water using hot water from a boiler or a solar heated water circuit.
Through the materials of the exchanger, which separate the working media, heat is transported through conduction.
While an air-cooled heat exchanger cools a liquid by passing cool air through a core of fins, a shell and tube heat exchanger moves fluids over and through tubes.
What variations of Heat Exchanger are available?
There are different variations of heat exchangers available, however TCW Group (PMT HVAC (M) Sdn Bhd) primarily supplies these three.
1. Shell and Tube Cooler, Shell and Tube Condenser;
Shell and Tube Heat Exchangers consist of a large number of small tubes which are located within a cylindrical shell. The tubes are positioned into the cylinder using a tube bundle or "tube stack" with fixed tube plates.
Shell and Tube Cooler comes with insulation, act as a cooling heat exchanger. While Shell and Tube condenser act as a heating heat exchanger
2. Air Cooled Cooling or Heating Coil
Air Cooled Heat Exchangers are commonly used in Air Handling Units, Air Cool Package, Air Cool Split Unit, Air Cool Chiller, or Fan Coil Unit.
3. Tube in Tube Condenser
Tube in Tube Heat Exchangers are commonly used in Water Cool Package
How is a Heat Exchanger designed?
To be able to select a heat exchanger, we need to know.
Primary circuit fluid type, temperature, and flow rate (usually the hot fluid)
What you want to take out of the primary circuit (Heat dissipation or a target outlet temperature)
Secondary circuit fluid type, temperature, and flow rate (usually the coolant)
Only the fundamentals are covered in the fields above. You should inform PMT HVAC of any pressure loss restrictions and any additional unique requirements when putting up an inquiry.
Marine Heat Exchangers
A marine heat exchanger operates similarly to a cooler made for freshwater use; the primary difference for the designer is that the marine heat exchanger needs to be resistant to erosion or corrosion brought on by sea water.
This means that materials like 90/10 Cupro-Nickel, 70/30 Cupro-Nickel, Bronze, and Titanium that come into contact with sea water must be appropriate.
When designing a marine heat exchanger, there are additional considerations that must be made. One is the velocity; if it is too low, sand and other particles run the risk of obstructing the tubes.
On the other hand, if it moves too quickly, the same particles can quickly destroy the tube plate and tubes. Installing a sacrificial anode, which PMT HVAC can provide upon request, can offer further protection.
This will be inserted into the drain plug's usual threaded hole, which is in direct touch with the flow of seawater.
What fluids can a Heat Exchanger operate with?
The type of heat exchanger being utilised and the materials that are available will determine whether a fluid is suitable for a heat exchanger.
The majority of fluids, including oil, water, water glycol, and sea water, can be used with standard PMT HVAC exchangers.
Acids, chlorinated sea water, refrigerants, and other more corrosive fluids will need the use of alternative materials, such as stainless steel and titanium.
What is temperature Cross Over?
The situation in which the temperatures of the two circuits in a liquid-cooled heat exchanger start to overlap is referred to as temperature cross over.
As the efficiency of a cooler will be much decreased when the temperatures cross over, this can be a crucial consideration in the design of a heat exchanger.
For applications where temperature cross-over cannot be prevented, a plate heat exchanger is frequently the best choice.
The table above shows that the temperature of the cooling water exit is a little bit higher than the temperature of the oil outlet. Increasing the coolant's flow rate is one easy technique to solve this problem and boost the oil cooler's effectiveness.
The water output temperature would drop to 43°C in this example if the water flow rate was increased to 25 L/min.
How to make a heat exchanger more efficient?
There are various different methods to describe heat exchanger efficiency, but when it comes to thermal performance, there are a few important things to keep in mind.
1. Temperature differential
When designing a heat exchanger, understanding the difference between the hot fluid and coolant is crucial. Always maintain a cooler fluid temperature than the hot fluid.
More heat will be removed from the hot fluid when the coolant temperature is lower than when it is higher.
The same logic holds true for heat exchangers: if you had a glass of drinking water at room temperature, for instance, it would be much more efficient to cool it down with ice than with cool water.
2. Flow rate
The fluid fluxes in both the main and secondary sides of the heat exchanger are a significant additional component.
A higher flow rate will increase the exchanger's capacity to transfer heat, but it also entails a higher mass, which may make it harder to remove energy while also increasing velocity and pressure loss.
3. Installation
The manufacturer's instructions should always be followed while installing a heat exchanger.
For shell and tube heat exchangers, the coolant should enter at the lowest inlet position (as shown in the diagrams above) to ensure that the heat exchanger is always full of water.
In general, the most efficient way to install a heat exchanger is with the fluids flowing in a counter-current arrangement (so if the coolant is travelling left to right, the hot fluid travels right to left).
When installing a cooler for air-cooled heat exchangers, it's crucial to take the air flow into account because any obstructed core area would reduce cooling capacity.
In Summary
A heat exchanger is a device that is used to transfer heat from one fluid to another. It is a common component in many different types of systems, including HVAC systems, power plants, and refrigeration units.
There are several different types of heat exchangers, each with its own unique design and characteristics.
Heat exchangers are an important part of many industrial and commercial processes, and they play a vital role in maintaining the proper temperature and efficiency of these systems. Feel free to contact us to know more.
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