Difference between plate heat exchanger and shell and tube heat exchanger-2
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2. Classification of plate heat exchangers:
(1) Plate heat exchangers are compact heat exchangers based on the heat exchange area per unit space, mainly compared with shell and tube heat exchangers. Conventional shell and tube heat exchangers occupy a large space.
(2) According to the process use, there are various names: plate heater, plate cooler, plate condenser, plate preheater.
(3) According to the process combination, it can be divided into one-way plate type and multi-way plate type.
(4) According to the flow direction of the two media, it can be divided into parallel plate heat exchanger and reverse flow plate heat exchanger. The latter is more commonly used.
(5) According to the size of the impeller gap, it can be divided into wide gap plate type and wide gap plate type.
(6) There are more detailed differences in plate heat exchangers, which cannot be repeated. Please refer to: Corrugation form of plate heat exchanger.
(7) According to whether it is a set of integral products, it can be divided into single plate type and plate type.
3. Characteristics.
1. Features of shell and tube heat exchanger:
(1) High thermal efficiency, the thermal conductivity coefficient is 6000-8000W/(m2·k).
(2) Made of stainless steel, with a service life of up to 20 years.
(3) Converting laminar flow into turbulent flow can improve heat transfer efficiency and reduce thermal resistance.
(4) Rapid heat conduction, high temperature resistance (400℃), and high pressure resistance (2.5 MPa).
(5) Compact structure, small footprint, light weight, easy installation, and saving civil engineering investment.
(6) Flexible design, complete specifications, practical, and cost-saving.
(7) Wide range of applications, suitable for pressure, temperature range and heat exchange of different media.
(8) Low maintenance cost, simple operation, long cleaning cycle, and easy cleaning.
(9) Nano thermal film technology can significantly improve the heat transfer coefficient.
(10) Widely used in thermal power, mining, petroleum and chemical, urban centralized heating, food and medicine, energy electronics, machinery and light industry, etc.
(11) The copper tube with fins rolled on the outer wall of the heat exchange tube has high thermal conductivity and large heat transfer area.
(12) The guide plate guides the shell-side fluid to flow continuously through the heat exchanger. The distance between the guide plates can be adjusted according to the flow rate. Its structure is sturdy and can meet the shell-side flow heat exchange with large or even ultra-large flow and high pulsation rate.
(13) The shell-side liquid is oily and suitable for low viscosity and clean heat transfer oil.
Teflon heat exchanger
2. Characteristics of plate-type Teflon heat exchanger:
(1) High thermal conductivity.
Because the different corrugated plates are reversed, complex channels are formed, so that the fluid between the corrugated plates flows in a three-dimensional rotating flow, and turbulence will occur at a lower Reynolds number (Re=50-200), so the thermal conductivity is high, usually considered to be 3-5 times that of the shell and tube type.
(2) The logarithmic mean temperature difference is large and the end temperature difference is small.
In a shell and tube heat exchanger, there are two flows between the tube sections and the tube sections. Generally, they are all lateral flows, and the correction coefficient of the logarithmic mean temperature difference is very small. Plate heat exchangers are mostly parallel flows or countercurrent flows, and the correction coefficient is generally around 0.95. In addition, the flow of cold flow and hot flow in the plate heat exchanger is parallel.
The hot surface and the absence of bypass make the temperature difference at the end of the plate heat exchanger small, usually below 1°C for shell and tube heat exchangers, and below 5°C for shell and tube heat exchangers.
(3) Less land occupation.
The plate heat exchanger has a compact structure, and the heat transfer area per unit volume is 2-5 times that of the shell and tube heat exchanger. Unlike the shell and tube heat exchanger, it does not require maintenance for the extraction tube bundle. In this way, the occupied area of the plate heat exchanger is about 1/5-1/8 of that of the shell and tube heat exchanger to achieve the same heat transfer capacity.
(4) The heat exchange area or combination can be easily changed.
The purpose of increasing or decreasing the heat transfer area can be achieved by simply adding or reducing a few heat plates. For the heat transfer area of a shell and tube heat exchanger, the required process combination can be achieved by changing the plate shape layout or replacing multiple plate types. It is almost impossible to increase the heat transfer area of a shell and tube heat exchanger.
(5) Light weight.
The plate thickness of a plate heat exchanger is between 0.4 and 0.8 mm, while the thickness of a shell and tube heat exchanger is between 2.0 and 2.5 mm. The shell and tube heat exchanger is heavier than the plate heat exchanger frame. The plate heat exchanger usually accounts for only about 1/5 of the weight of the shell and tube.
(6) Low price.
The plate heat exchanger has the same material and the same heat transfer area, and the price is 40% to 60% cheaper than the shell and tube heat exchanger.
(7) Easy to manufacture.
After stamping, the heat transfer plate of the plate heat exchanger is highly standardized and can be mass-produced. Shell and tube heat exchangers are usually handmade.
8) Easy to clean.
After the pressure bolts of the plate heat exchanger tube bundle are loosened, the plate heat exchanger tube bundle can be loosened and the plate heat exchanger can be disassembled for mechanical cleaning. This method is suitable for heat exchange processes that require frequent cleaning of equipment.
9) Low heat loss.
In the plate heat exchanger, only the shell plate is in contact with the heat exchange plate, the heat loss can be ignored, and no insulation measures are required.
