Heat Exchangers

What Is Heat Exchangers
 

Introduction

A heat exchanger, in its simplest form, is any device that moves heat from one medium to another; for instance, a Hydraulic Oil Cooler transfers the heat of heated oil to cool water or air. Pool water can also be heated via a heat exchanger that draws hot water from a boiler or solar heated water circuit. Through the materials of the heat exchanger, heat is exchanged between the two media. When cooling liquid, a shell and tube heat exchanger directs the fluid through and over the tubes, whereas an air cooled heat exchanger directs the air through a core of fins.
 

Types of Heat Exchangers
 

1. Micro channel heat Exchanger 

They are multi-pass parallel-flow heat exchangers, and its components are input and exit manifolds, tubes with multiple ports, hydraulic channels thinner than 1 mm in diameter, and fins. When joining these components, a controlled environment brazing procedure is typically used.
 

2. Phase Change heat Exchanger 

Due to the negligible size change between the solid and liquid states, this phase transition typically occurs. This phase transition acts as a buffer, allowing for additional heat to be acquired while maintaining a steady temperature. When it comes to energy storage, phase change materials really shine.
 

3. Adiabatic heat Exchanger 

This particular heat exchanger finds widespread application in manufacturing. One side of the heat exchanger stores heat in a fluid while the other side transfers it elsewhere.
 

4. Finned heat exchanger 

To better conduct heat in liquids with low thermal conductivity, like air, finned tube heat exchangers are built to refer to the highest heat transfer surface area with the exchanged heat. It's made up of a network of tubes with fins attached to maximize the surface area in contact with the external fluid and the surface area in contact with the fluid inside the tube, allowing for more efficient heat transfer.
 

5. Pillow Plate heat Exchanger 

Products in manufacturing facilities can benefit from both their cooling and heating capabilities with these. As they inflate, the wavy "pillow-shaped" surface of these heat exchangers is formed. Typical applications for these include reboilers, water chillers, solids dryers, and so on. The cooling of milk in huge stainless steel bulk tanks is a popular application of this type of heat exchanger.
 

6. Plate Heat Exchanger 

These heat exchangers use metal plates to transfer heat, as their name implies. The fluids in motion can move freely because of the channels formed by the metal plates. 

Plate Heat Exchangers are constructed from many individual flat plates that are linked together to create a network of channels via which heat and cold can be transferred. This is because the heat penetrates the surface, creating a barrier between the hot and cold media. 

For this reason, the energy required to heat or cool liquids and gases is quite small. Compared to shell and tube, they can sometimes be cheaper and take up less space. The water heating and air conditioning industries rely heavily on these.
 

7. Direct Heat Exchanger 

In the absence of an insulating wall, direct heat exchangers facilitate the transfer of heat between two streams of hot and cold currents. The heat transfer process occurs concurrently when the hot and cold liquids are mixed together, eliminating the need for a heat exchanger. There are a few types of cooling towers and jet condensers.
 

8. Indirect Heat Exchanger 

Because of the impermeability of the barrier between the two common fluids, the temperature difference between the two common fluids can be measured indirectly using an indirect heat exchanger. Tubes, plates, and other heat-insulating materials maintain the fluids being exchanged at different temperatures.
 

9. Double Pipe heat Exchanger 

The inner pipe works as a conductive barrier, allowing one liquid to flow through it while another flows between it and the outer pipe. It finds widespread application in manufacturing, cooling technology, refrigeration, and other areas due to its high efficiency and low capital cost.
 

10. Tube in tube heat exchanger 

The heating and cooling needs of sludge including fibers and particles are met by a tube-in-tube heat exchanger. 

With the introduction of tube in tube heat exchangers, a tube is introduced inside of a tube. Within the tube, the product medium floats countercurrent to the service medium as the tube operates. The product tube may be plain or folded. 

This innovative layout saves bulk, boosts performance, and stops thermal exhaustion.
 

11. Shell and Tube heat exchanger 

These heat exchangers are the most popular and adaptable ones used today. Within a cylindrical housing, this heat exchanger's many tubes come into direct thermal contact with the two working fluids, exchanging heat in the process.

 This configuration allows one fluid to move inside the tubes while another moves outside the shell. A shell and tube heat exchanger is a small, low-maintenance, and high-performing heat exchanger design. Preheating, oil cooling, and steam production are all possible with this heat exchanger.
 

What Is the Principle of Heat Exchanger.
 

Heat exchangers are predicated on the principles outlined in the laws of thermodynamics.

• 1. In a state of thermal equilibrium, all thermodynamic systems have the same temperature, as required by the Thermodynamics. If two systems are in thermodynamic equilibrium with a third, then the temperatures of all three must be equal.
   
• 2. It is impossible to create or destroy energy, according to the First Law of Thermodynamics, yet energy can be transferred from one medium to another in the form of heat.
   
• 3. A closed thermodynamic system has a natural, invariable tendency to rise in entropy over time, as described by the Second Law of Thermodynamics, which establishes entropy (S) as an extra attribute of thermodynamic systems.

What Are the Advantages of Heat Exchanger.
 

1. Minimal Operating Cost 

Heat exchangers do not need to be maintained as frequently as air conditioners do since they do not employ complex external equipment and because they are designed to eliminate the majority of pollution. 

They are also extremely durable, with the ability to outlive the majority of air conditioning units by many orders of magnitude before requiring maintenance, repair, or replacement.
 

2. Lower Environmental Impact 

Heat exchangers have to be kept in a constant state of operation in order for them to be successful in preventing high-powered control panels from overheating. 

The fact that modern heat exchangers do not need supplementary apparatus to function well, such as air conditioning or air compression units, is one of the most significant advantages offered by these devices. 

As a result, in comparison to other, more conventional techniques of temperature control, they consume an enormous amount less energy and generate almost no pollution.
 

3. Smaller Spatial Footprint 

It would appear that more powerful also means smaller as a result of the progression of modern technology. 

This includes smaller personal devices, smaller and more adaptable manufacturing equipment, and a number of other examples. As the amount of space available in electrical cabinets decreases, the potential for heat pockets and the subsequent damage to electrical components increases.

 As a result, there is an increased demand for cooling solutions that are both more compact and more effective, such as heat exchangers.
 

4. High Heat Transfer Coefficient 

The heat transfer coefficient of the air-cooled heat exchanger is high, and it is commonly estimated to be three to five times higher than the heat transfer coefficient of the shell-and-tube heat exchanger. 

The heat exchange area of an air-cooled heat exchanger is much less than half of the heat exchanges area of a shell-and-tube heat exchanger while performing the identical heat exchange duty;
 

5. Large Temperature Difference Correction Coefficient 

The flow patterns of the two fluids in a shell-and-tube heat exchanger are typically described as being cross-flowing, as they take place in the shell and tube sections, respectively.

 The logarithmic mean temperature difference needs to be adjusted since additional investigation reveals that the flow on the shell side is a mixed flow and the flow along the tube length is a multi-strand flow. In most cases, the factor is not very significant.

Air-cooled heat exchangers typically have either a countercurrent or concurrent fluid flow pattern.

FAQs: Heat Exchangers
 

Q. What are heat exchangers used for?

Ans: There are a wide variety of engineering uses for heat exchangers, including cooling, heating, air conditioning, power generation, waste heat recovery, vehicle radiators, and chemical and food processing.
 

Q. What is heat exchanger and example?

Ans: Shell & Tube is the most common heat exchanger example that uses for parallel arrangements of tubes. 
 

Q. What liquid is used in heat exchangers?

Ans: Heat transfer fluids include liquids like synthetic oil, molten salt, and water. Due to its large thermal capacity and low viscosity, water makes for an excellent heat transfer fluid.
 

Q. Which type of heat exchanger is mostly used?

Ans: Shell and Tube are the main heat exchanger that is mostly used in food industry.