A heat exchanger is a device that transfers heat between fluids by passing hot and cold fluids across opposite sides of a piece of metal. The heat is conducted through the metal into another fluid without direct contact between the fluids. Several factors contribute to more efficient heat transfer, including high fluid velocity, turbulence, surface area contact, and temperature differences. However, the effectiveness of heat exchangers varies depending on the specific application.
Plate and Frame Heat Exchanger
A plate and frame heat exchanger, also known as a plate heat exchanger, uses metal plates to transfer heat between two fluids. This type of heat exchanger is suitable for applications with air or gas and lower velocity fluid flow. The design features corrugated parallel plates that control the flow of hot and cold fluids on the surface of the plates through gaskets.
The plates are compressed together by the frame plate and pressure plate using tightening bolts. This simple mechanical design allows for easy cleaning and capacity adjustment. Plate and frame heat exchangers generally have a smaller volume and cost compared to shell and tube heat exchangers. They are commonly used for medium and low-pressure fluids.
Plate and frame heat exchangers are ideal for heating low to medium viscosity fluids due to the narrow paths between the plates and the turbulent flow created by the corrugated design. The wider gap between the plates helps maintain flow requirements and allows particles to pass through without impeding flow.
- Low initial purchase cost
- Multiple configurations available
- Higher heat transfer efficiency
- Reduced fouling due to high turbulence
- Allows for significant temperature crossover
- Requires less space
- Narrow allowable pressure and temperature ranges
- Potential for clogging/fouling in narrow flow paths
- Special opening and closing procedures for gasket units
- Critical material choice due to thin tube walls
- Low to medium viscosity products with minimal particles, such as milk, cream, beverages, and beer
Shell and Tube Heat Exchanger
The shell and tube heat exchanger is one of the most widely used types in the industry. It consists of a series of parallel tubes (tube bundles) enclosed within a sealed cylindrical pressure vessel (shell). One fluid flows through the smaller tubes, while the other flows around the outside of the tubes within the shell.
Shell and tube heat exchangers are further classified based on the number of shells and tubes involved. They are commonly used for high-pressure applications with pressures above 30 bar and temperatures above 260°C, as they are designed to withstand high pressures.
These heat exchangers have small-bore tubes installed between two tube sheets, with the main fluid flowing through them. The secondary fluid travels over the surface of the tubes within the enclosure. Shell and tube heat exchangers can be used to transfer heat in various applications, including nuclear engineering and power generation.
- Widely known and understood
- The most common type of heat exchanger in use
- Allows for the widest range of pressure and temperature
- Sturdy mechanical structure
- Lower heat exchange efficiency compared to other types
- Potential for flow-induced vibration
- Less suitable for temperature crossing conditions
- Possibility of stagnant zones leading to corrosion on the shell side
- Uneven flow distribution
- Low to medium viscosity products with varying particle sizes, such as pulp, lotions, and dairy products
Double Tube Heat Exchanger
A double tube heat exchanger is a form of shell and tube heat exchanger. It consists of two or more concentric cylindrical pipes and tubes, with one larger tube and one or more smaller tubes. One fluid flows through the smaller tubes, while the other flows around them within the larger tubes.
This type of heat exchanger is known for its simplicity and affordability. Its compact size makes it suitable for tight spaces and offers flexibility in manufacturing process layout.
While double tube heat exchangers are simple and inexpensive to design and maintain, they have lower efficiency and larger footprints compared to more efficient heat exchangers like shell and tube heat exchangers.
- Good heat transfer efficiency at a low capital cost
- Smaller size, requiring less maintenance space
- Standardized components for easy repairs and maintenance
- Flexible design for easy additions and removals
- Suitable for high pressure and high temperature applications
- Allows for thermal expansion without expansion joints
- Typically used in counterflow designs and may not be suitable for all applications
- Limitations in heat transfer for complex designs and high heat loads
- Potential for leakage (when paired with more units)
- High temperature and high-pressure applications, such as boilers and compressors
- Sensible heat and cooling in engineered systems
As we’ve discussed, heat exchanger styles vary based on various factors, making the right choice for your brewing process challenging. In a future blog post, we will explain how breweries should select a heat exchanger. If you’re planning to open or expand a brewery, you can directly contact us for a turnkey solution or an expansion plan. Our engineers will design and manufacture brewery equipment tailored to your brewing process, providing you with a comprehensive turnkey solution.