What is a plate heat exchanger?
Release time:
2022-02-15 12:34
Source:
A plate heat exchanger is a heat exchanger made up of a number of corrugated metal plates stacked together. Thin rectangular channels are formed between the plates, through which heat is exchanged. Plate heat exchangers are ideal equipment for liquid-liquid and liquid-vapor heat exchange. They have the advantages of high heat exchange efficiency, low heat loss, compact structure, small footprint, wide application, and long lifespan. Under the same pressure drop, the heat transfer coefficient is 3-5 times higher than that of a tube heat exchanger, the footprint is one-third that of a tube heat exchanger, and the heat recovery rate can be as high as 90% or more.
The main types of plate heat exchangers include frame type (removable) and brazed type, and the plate types mainly include benevolence type, horizontal flat type and tumor type.
What is the structural principle of a plate heat exchanger?
A removable plate heat exchanger consists of multiple stamped corrugated plates evenly spaced, sealed on all sides with gaskets, and overlapped and compressed by a frame and pressure spiral. The four corner holes of the plates and gaskets form the fluid distribution pipes and collection pipes, while reasonably separating the hot and cold fluids so that the channels on both sides of each plate flow separately, performing heat exchange through the plates.
The optimized design calculation of a plate heat exchanger is to reasonably determine the corresponding model, process, and heat transfer area, making NTUp equal to NTUE, when the temperature difference ratio NTUE is known.
What are the characteristics of a plate heat exchanger?
(Comparison of plate heat exchanger with shell and tube heat exchanger)
A. High heat transfer coefficient;
Due to the complex flow passages formed by the reversal of different plates, the fluid rotates in three dimensions in the passages between the plates, generating turbulence at low Reynolds numbers (generally Re = 50-200), resulting in a high heat transfer coefficient, typically considered to be 3-5 times that of a shell-and-tube type.
B. Large logarithmic mean temperature difference, small terminal temperature difference.
In shell-and-tube heat exchangers, the two fluids flow respectively inside and outside the tubes, usually cross-flow, and the logarithmic mean temperature difference correction factor is small. However, plate heat exchangers are mostly parallel flow or counter-current flow, and the correction factor is generally about 0.95. In addition, the cooling and heating fluids flow in the plate heat exchanger parallel to the heat transfer surface without lateral flow, so there is no dead end in the plate heat exchanger.
C. Small installation area.
Plate heat exchangers have a compact structure, and the heat exchange area per unit volume is 2-5 times that of tube heat exchangers. They also don't require the space for tube bundle extraction for maintenance, as in shell-and-tube exchangers. Therefore, for the same heat exchange, the footprint of a plate heat exchanger is about 1/5 to 1/8 that of a tube heat exchanger.
D. The heat transfer area or stage combination can be easily changed.
Adding or removing a few plates can increase or decrease the heat exchange area. By changing the arrangement of the plates or replacing a few plates, the desired process combination can be obtained to adapt to new heat exchange conditions. The heat transfer area of a shell-and-tube heat exchanger is almost impossible to increase.
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