In fields such as industrial production, HVAC (Heating, Ventilation, and Air Conditioning), and refrigeration, heat exchangers serve as core equipment for heat transfer. Their performance directly affects the energy efficiency and operating costs of systems. As two common types of high-efficiency heat exchange equipment, plate-shell heat exchangers and brazed plate heat exchangers share functional commonalities while also exhibiting significant differences in structure, application scenarios, and other aspects. Starting from the basic principles and structures of both, this article will conduct an in-depth analysis of their similarities and differences, providing references for equipment selection in practical applications.

I. Basic Characteristics of the Two Types of Heat Exchangers

(I) Plate-Shell Heat Exchangers

A plate-shell heat exchanger is a new type of heat exchanger that combines the stability of shell-and-tube heat exchangers and the high efficiency of plate heat exchangers. Its structure consists of two parts: a "plate bundle" and a "shell". The plate bundle, as the core heat exchange component, is composed of multiple stamped metal corrugated plates joined together by welding or riveting, forming a number of independent flow channels. The shell, on the other hand, is a pressure-bearing outer casing (either cylindrical or square) that encloses the plate bundle and withstands the system pressure.

During operation, two fluids with different temperatures enter different flow channels of the plate bundle respectively, and heat exchange occurs through the metal corrugated plates. The high-temperature fluid releases heat and decreases in temperature, while the low-temperature fluid absorbs heat and increases in temperature. Due to the design of the corrugated plates, which increases the heat exchange area, and the turbulent flow of the fluid within the channels, the heat exchange efficiency of plate-shell heat exchangers is much higher than that of traditional shell-and-tube heat exchangers. Meanwhile, the shell structure endows the equipment with strong pressure-bearing capacity, enabling it to adapt to medium and high-pressure working conditions (usually with a design pressure of 1.6 - 10MPa). Currently, plate-shell heat exchangers are widely used in fields such as petrochemical engineering, power engineering, and marine refrigeration, and are particularly suitable for scenarios requiring high heat exchange efficiency under high-temperature and high-pressure conditions.

(II) Brazed Plate Heat Exchangers

Brazed plate heat exchangers are a type of plate heat exchanger, with their core feature being the use of a "brazing" process to connect the plates. The equipment is composed of multiple stacked metal plates with corrugations and sealing grooves. The plates are fixed together by welding with brazing materials such as copper or nickel at high temperatures, forming alternating flow channels for hot and cold fluids.

During operation, hot and cold fluids flow in their respective flow channels and transfer heat through the metal plates. The design of the corrugated plates not only increases the heat exchange area but also causes the fluid to generate intense turbulence within the channels, breaking the boundary layer and significantly improving the heat transfer coefficient. Additionally, the brazed sealing method replaces the rubber gaskets used in traditional plate heat exchangers, giving brazed plate heat exchangers better performance in withstanding high temperatures and pressures (suitable for temperatures ranging from -196℃ to 300℃ and a design pressure of up to 4MPa). Owing to their small size, light weight, and high heat exchange efficiency, brazed plate heat exchangers are commonly used in small and medium-sized heat exchange scenarios such as household air conditioners, automotive air conditioners, refrigeration systems, and heat pump units. They can also replace traditional heat exchangers in some industrial fields to save space.

II. Similarities Between Plate-Shell Heat Exchangers and Brazed Plate Heat Exchangers

(I) Consistent Core Function

The essential function of both is to achieve heat transfer between two or more fluids. Through reasonable flow channel design, they complete the process of "cooling the high-temperature fluid and heating the low-temperature fluid" without mixing the fluids, meeting the process requirements of heating, cooling, condensation, evaporation, etc., in industrial production or daily life.

(II) Similar Heat Transfer Principles

Both are based on the principle of "separate-wall heat transfer". That is, hot and cold fluids are separated by a metal wall (the corrugated plates of plate-shell heat exchangers and the plates of brazed plate heat exchangers). Heat is transferred from the high-temperature fluid to the low-temperature fluid through the metal wall, avoiding the risk of contamination caused by direct contact between the fluids. This makes them suitable for scenarios with high requirements for fluid purity.

(III) Common Design for High-Efficiency Heat Exchange

To improve heat exchange efficiency, both types of heat exchangers adopt the design concept of "increasing heat exchange area + enhancing fluid turbulence". The corrugated plates of plate-shell heat exchangers and the corrugated plates of brazed plate heat exchangers both increase the heat exchange area per unit volume through their concave-convex structures. At the same time, the corrugated structure forces the fluid to change its flow direction in the channels, creating a turbulent flow state, which reduces thermal resistance. As a result, their heat exchange efficiency is much higher than that of traditional shell-and-tube heat exchangers (under the same volume, the heat exchange efficiency is usually 2 - 5 times that of shell-and-tube heat exchangers).

III. Differences Between Plate-Shell Heat Exchangers and Brazed Plate Heat Exchangers

(I) Differences in Structure and Connection Methods

This is the most core difference between the two. A plate-shell heat exchanger is composed of a "plate bundle + shell". The corrugated plates in the plate bundle are mostly fixed by welding or riveting and are entirely enclosed within a pressure-bearing shell. Its structure is more similar to the "modular + outer shell" form of shell-and-tube heat exchangers. In contrast, a brazed plate heat exchanger has no independent shell. It is formed by directly welding multiple plates through a brazing process, with no additional outer shell surrounding the plates, resulting in a more compact and lightweight structure.

In terms of connection sealing, the connections between the plate bundle and the shell, as well as between the plates themselves in a plate-shell heat exchanger, all use welded sealing. This provides high sealing reliability and allows the equipment to adapt to working conditions involving repeated start-ups/shutdowns or pressure fluctuations. Brazed plate heat exchangers rely on the welding fixation of brazing materials. Although their sealing performance is better than that of traditional plate heat exchangers with rubber gaskets, the brazed joints may experience aging or corrosion when exposed to high temperatures, high pressures, or corrosive fluid environments for a long time, leading to a slightly higher sealing risk compared to plate-shell heat exchangers.

(II) Different Ranges of Applicable Pressure and Temperature

Due to the presence of a pressure-bearing shell and the strong structural stability of the plate bundle, plate-shell heat exchangers have a wider range of applicable pressure and temperature. Their design pressure can usually reach above 10MPa, and the maximum applicable temperature can be up to 500℃, making them capable of meeting medium-high pressure and high-temperature working conditions such as those in petrochemical engineering and high-pressure steam heat exchange. In contrast, brazed plate heat exchangers have no shell for protection, and their plates are relatively thin (usually 0.3 - 0.8mm), resulting in relatively weaker pressure and temperature resistance. Their design pressure generally does not exceed 4MPa, and the maximum applicable temperature is approximately 300℃, making them more suitable for small and medium-power heat exchange scenarios under medium-low pressure and medium-low temperature conditions.

(III) Differences in Volume, Weight, and Installation Flexibility

Under the same heat exchange power, brazed plate heat exchangers have a smaller volume and lighter weight. Due to the absence of a shell structure and the dense arrangement of plates, their volume is usually only 1/3 - 1/5 that of plate-shell heat exchangers, and their weight is about 1/2 - 1/4 of the latter. They are particularly suitable for scenarios with limited installation space (such as automotive air conditioners and household heat pumps). Plate-shell heat exchangers, on the other hand, include a shell and a relatively thick plate bundle, resulting in a larger volume and heavier weight. They require more space for installation and have certain requirements for the load-bearing capacity of the foundation.

(IV) Differences in Maintenance Costs and Service Life

Plate-shell heat exchangers have a relatively complex structure, and it is difficult to disassemble the plate bundle and the shell. If the internal flow channels become blocked or fouled, the cleaning and maintenance costs are relatively high. However, since they are usually made of corrosion-resistant materials such as stainless steel and titanium alloy, and their welded structure is firm, they have a longer service life (generally 15 - 20 years).

Brazed plate heat exchangers have a simple structure. However, if the flow channels are blocked, due to the non-detachable brazed connection between the plates, individual plates cannot be cleaned or replaced separately, and the entire equipment usually needs to be replaced. This leads to potentially higher long-term maintenance costs. Their service life is greatly affected by the performance of the brazing material and the corrosiveness of the fluid, generally ranging from 8 - 15 years, which is shorter than that of plate-shell heat exchangers.

(V) Differences in Focus on Application Scenarios

Due to their characteristics of withstanding high temperatures, high pressures, and corrosion, plate-shell heat exchangers are mainly used in large or heavy-duty equipment in industrial fields, such as catalytic cracking units in petrochemical engineering, turbine cooling in power systems, and central cooling systems in ships. Brazed plate heat exchangers, on the other hand, with their advantages of small size and high efficiency, are more suitable for small and medium-sized civil or light industrial scenarios, such as household air conditioners, automotive refrigeration, commercial freezers, and small heat pump units. They can also be used in auxiliary heat exchange links in industrial fields (such as hydraulic oil cooling).

IV. Conclusion

As high-efficiency separate-wall heat exchange equipment, plate-shell heat exchangers and brazed plate heat exchangers are highly consistent in terms of heat transfer principles and core functions, and both can meet the demand for high-efficiency heat exchange in modern industry and daily life. However, they exhibit significant differences in structural design, temperature and pressure resistance, maintenance costs, and application scenarios. Plate-shell heat exchangers have the advantages of "high stability, long service life, and a wide range of applications" and are suitable for industrial high-pressure and high-temperature working conditions. Brazed plate heat exchangers, on the other hand, are characterized by "lightweight, compactness, and high cost-effectiveness" and are more suitable for small and medium-sized civil or light industrial scenarios.

In practical equipment selection, a comprehensive judgment should be made based on specific working condition parameters (pressure, temperature, fluid properties), space constraints, maintenance requirements, and cost budgets. If it is necessary to cope with industrial scenarios involving high pressure, high temperature, and long-term stable operation, plate-shell heat exchangers are a more reliable choice. If a compact volume, high heat exchange efficiency, and mild working conditions are pursued, brazed plate heat exchangers are more advantageous.