HEAT EXCHANGE EQUIPMENT
A 'heat exchanger' is a device that facilitates the transfer of thermal energy from a hot fluid to a cold fluid, enabling the process of heating or cooling to occur. Inside the exchanger, the hot and cold fluids flow through separate channels, exchanging heat energy through convective heat transfer. As they flow, the temperature of each fluid changes, with the hot fluid cooling down and the cold fluid warming up.
Heat exchangers are ubiquitous in various industries, playing a crucial role in efficient energy transfer. Let's explore some examples of heat exchangers and their applications:
- Intercoolers and heaters: These heat exchangers are used in gas turbines and compressors to optimize performance. They account for approximately 15% of the total heat exchanger market in the power generation sector.
- Condensers and boilers in steam plants: These heat exchangers are essential in steam power plants, responsible for condensing steam and generating steam, respectively. They comprise around 20% of the heat exchanger market in the power generation sector.
- Evaporators: These heat exchangers are used in refrigeration systems, chemical processing, and desalination plants. They account for around 10% of the heat exchanger market in the HVAC and refrigeration sector.
- Regenerators: These heat exchangers are used in cryogenic applications, such as liquefying gases, and in the aerospace industry. They comprise a niche market, accounting for around 5% of the heat exchanger market in the aerospace sector.
- Automobile radiators: These heat exchangers are used in vehicles to cool the engine. They account for around 30% of the heat exchanger market in the automotive sector.
- Oil coolers of the heat engine: These heat exchangers are used in engines to cool the lubricating oil. They comprise around 20% of the heat exchanger market in the automotive sector.
- Milk chiller of a pasteurizing plant: These heat exchangers are used in dairy processing to cool milk. They account for around 10% of the heat exchanger market in the food processing sector.
According to market research, the global heat exchanger market is projected to reach $18.8 billion by 2025, growing at a CAGR of 6.5% from 2020 to 2025. The market is dominated by the following industries:
- Power generation: 35%
- HVAC and refrigeration: 25%
- Automotive: 20%
- Chemical processing: 10%
- Food processing: 5%
- Aerospace: 5%
Note:
- Developed Countries: USA, Germany, Japan, etc.- Developing Countries: China, India, Brazil, etc.
| Industry | Developed Countries | Developing Countries | Energy Handling (%) | Energy Optimization (%) | Emissions Reduction (%) | Energy Efficiency (%) |
|---|---|---|---|---|---|---|
| Power Production | 30% | 20% | 25% | 15% | 10% | 8% |
| Process, Chemical, and Food Industries | 25% | 15% | 20% | 12% | 8% | 6% |
| Electronics | 15% | 5% | 10% | 8% | 5% | 4% |
| Environmental Engineering | 10% | 5% | 8% | 6% | 4% | 3% |
| Waste Recovery | 7% | 3% | 5% | 4% | 3% | 2% |
| Manufacturing Industry | 15% | 10% | 12% | 9% | 6% | 5% |
| Air-Conditioning and Refrigeration | 12% | 8% | 10% | 8% | 5% | 4% |
CLASSIFICATION
Heat exchangers may be classified according to the following main criteria:
1. Nature of heat exchanger process
2. Flow arrangement
3. The physical state of fluids
4. Geometry and construction
1. Classification based on the Nature of the heat exchanger process
(i) Direct contact:
Heat transfer will occur by direct mixing of two fluids. This is preferred when the direct mixing is harmless or desirable.
Ex: cooling towers
(ii) Indirect contact:
Heat transfer will occur through a separating wall between two fluids
Ex: Regenerators and Recuperators
2. Classification based on Flow arrangement
According to the relative directions of two fluid streams, the heat exchangers are classified into the following three categories:
(i) Parallel flow or co-current flow heat exchangers
(ii) Counter-flow heat exchangers
(iii) Cross-flow heat exchangers
(i) In a parallel or co-current flow heat exchanger
As the name suggests, the two fluid streams (hot and cold) travel in the same direction. The two streams enter at one end and leave at the other end. The flow arrangement and variation of temperatures of the fluid streams in the case of parallel flow heat exchangers are shown in the below figure. It is evident from the figure that the temperature difference between the hot and cold fluids decreases from inlet to outlet.
In parallel flow, it is impossible to bring the cold fluid's outlet temperature nearly to the hot fluid's inlet temperature. This type of heat exchanger needs a large heat transfer area, so, it is rarely used in practice.
It is particularly useful when sudden cooling or sudden heating is required.
Examples: Oil coolers, oil heaters, water heaters, etc.
(ii) Counter-flow heat exchangers
In a counter-flow heat exchanger, the two fluids flow in opposite directions. The hot and cold fluids enter at the opposite ends. The flow arrangement and temperature distribution for such a heat exchanger are shown schematically in the below figure.
In this flow, it is possible to bring the cold fluid's outlet temperature nearly to the hot fluid's inlet temperature. This type of heat exchanger needs a small heat transfer area, so, it is widely used in practice.
Examples: Oil coolers, oil heaters, water heaters, etc.
(iii) Cross-flow heat exchangers
In cross-flow heat exchangers, the two fluids (hot and cold) cross one another in space, usually at right angles.
LMTD Calculator
Hot Fluid Inlet Temperature (°C)
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Cold Fluid Outlet Temperature (°C)