The plate heat exchanger is a highly efficient heat exchanger composed of a series of metal plates with a certain corrugated shape stacked together. Thin rectangular channels are formed between various plates, through which heat exchange takes place. Plate heat exchangers are ideal equipment for liquid-liquid and liquid-vapor heat exchange. It features high heat exchange efficiency, low heat loss, compact and lightweight structure, small floor space, wide application and long service life. Under the same pressure loss conditions, its heat transfer coefficient is 3 to 5 times higher than that of the tubular heat exchanger, its floor space is one-third of that of the tubular heat exchanger, and its heat recovery rate can be as high as over 90%.

Comparison between plate heat exchangers and shell and tube heat exchangers

a. High heat transfer coefficient;

Due to the fact that different corrugated plates are inverted with each other, they form complex flow channels, causing the fluid to flow in a rotational three-dimensional manner within the flow channels between the corrugated plates. This can generate turbulence at a relatively low Reynolds number (generally Re=50 to 200), resulting in a high heat transfer coefficient, which is generally considered to be 3 to 5 times that of the shell and tube type.

b. The logarithmic mean temperature difference is large, while the temperature difference at the end is small.

In shell and tube heat exchangers, the two fluids flow in the tube side and shell side respectively, and the overall flow is cross-flow, with a small logarithmic mean temperature difference correction coefficient. In contrast, plate heat exchangers mostly adopt co-current or counter-current flow patterns, and their correction coefficients are typically around 0.95. Additionally, the flow of cold and hot fluids in plate heat exchangers is parallel to the heat exchange surface without side flow. Therefore, the temperature difference at the end of the plate heat exchanger is small, and the heat exchange with water can be less than 1℃, while that of the shell and tube heat exchanger is generally 5℃fff.

c. Small floor area.

Plate heat exchangers have a compact structure. The heat exchange area per unit volume is 2 to 5 times that of shell and tube heat exchangers. Unlike shell and tube heat exchangers, they do not require a reserved maintenance area for extracting the tube bundle. Therefore, to achieve the same heat exchange capacity, the floor space occupied by plate heat exchangers is approximately 1/5 to 1/8 of that of shell and tube heat exchangers.

d. It is easy to change the heat exchange area or the combination of flow processes;

Just by adding or reducing a few plates, the purpose of increasing or decreasing the heat exchange area can be achieved. By changing the arrangement of the plates or replacing a few plates, the required process combination can be achieved to adapt to the new heat exchange conditions, while the heat transfer area of the shell and tube heat exchanger is almost impossible to increase.

e. Light weight;

The thickness of the plates in a plate heat exchanger is only 0.4 to 0.8mm, while the thickness of the heat exchange tubes in a shell and tube heat exchanger is 2.0 to 2.5mm. The shell of a shell and tube heat exchanger is much heavier than the frame of a plate heat exchanger. Generally, a plate heat exchanger weighs only about 1/5 of a shell and tube heat exchanger.

f. Low price;

Using the same materials and under the same heat exchange area, the price of plate heat exchangers is approximately 40% to 60% lower than that of shell and tube heat exchangers.

g. Convenient to make;

The heat transfer plates of plate heat exchangers are processed by stamping, with a high degree of standardization and can be mass-produced. Shell and tube heat exchangers are generally made by hand.

h. Easy to clean;

For frame-type plate heat exchangers, the plate bundle can be loosened simply by loosening the clamping bolts, and the plates can be removed for mechanical cleaning. This is very convenient for heat exchange processes that require frequent equipment cleaning.

i. Low heat loss;

In a plate heat exchanger, only the outer shell of the heat transfer plate is exposed to the atmosphere, so the heat dissipation loss can be ignored and no insulation measures are required. However, shell and tube heat exchangers have a large heat loss and require insulation layers.

j. Smaller capacity;

It is approximately 10% to 20% of that of shell and tube heat exchangers.

k. Large pressure loss per unit length;

Due to the small gap between the heat transfer surfaces and the concave and convex appearance on the heat transfer surfaces, the pressure loss is greater than that of the traditional smooth tubes.

1. Not prone to scaling;

Due to the thorough turbulence inside, it is not prone to scaling, and its scaling coefficient is only 1/3 to 1/10 of that of shell and tube heat exchangers.

m. The working pressure should not be too high, as leakage may occur.

Plate heat exchangers are sealed with gaskets. The working pressure generally should not exceed 2.5MPa, and the medium temperature should be below 250℃; otherwise, leakage may occur.

n. Prone to clogging;

Due to the narrow channels between the plates, usually only 2 to 5mm, when the heat exchange medium contains larger particles or fibrous substances, the channels between the plates are prone to being blocked.