Selection of Plate Heat Exchanger and Its Components

Selection of Plate Heat Exchanger and Its Components

22 Feb 2019

Selection of plate type heat exchanger types:
There are many kinds of plate heat exchangers, each of which has a suitable working condition, which should be chosen first in engineering design.

The brazed heat exchanger can be selected when the temperature is above 200 ℃and the pressure is more than 2 MPa. If the total area is large, the fully welded heat exchanger can also be selected.

When the temperature is over 300 ℃ and the pressure is over 3.5 MPa, we should choose plate shell heat exchanger.

Shallow groove ripple can be used for the condition of small temperature difference at the end, and removable plate heat exchanger can be used for the case of frequent disassembly. Asymmetric plate heat exchangers can be selected for those with large flow difference.

Selection of plate type:
1. Mainly consider the heat transfer effect and pressure drop requirements to be achieved.
2, If the pressure requirement is above 1.2 MPa, herringbone corrugation is chosen in most cases.
3. If the pressure drop requirement is small and the heat transfer effect requirement is not high, the straight ripple can be chosen.
4. If there are more impurities in the medium, spherical corrugation can be chosen.
5. For pressure drop and heat transfer effect, there are certain requirements of the working conditions, but also the choice of heat mixing plate.

Selection of monolithic area:
1. Choosing a reasonable area of single sheet can avoid too many or too few total sheets.
2. Too many sheets will make the equipment occupy too much space.
3. Too little may increase the number of processes and pressure drop.
4. At the same time, the size of the single chip area is also related to the size of the corner hole to a certain extent, which directly affects the change of flow rate and flow rate.

The relation between veneer area and processing capacity

Veneer area/m2

0.1

0.2

0.3

0.5

0.8

1.0

1.6

2

Diameter of corner hole/mm

40~50

65~90

80~100

125~150

175~200

200~250

300~350

About400

Maximum throughput per unit/m3/h

27~42

71~137

108~170

265~380

520~680

680~1060

1530~2080

About2700


Velocity selection:
1. The velocity on the mainstream line is about 4-5 times of the average velocity.
2. Under normal conditions, the flow velocity between plates ranges from 0.2 m/s to 1.0 m/s.
3. In order to obtain better heat transfer effect and reduce heat transfer area, a large value should be taken when the pressure drop is allowed.

Process selection:
1. In the case of symmetrical plate shape and equal flow rate of hot and cold media, it is advisable to adopt equidistant arrangement so that the flow direction of medium is totally counter-current.
2. When the flow rate difference between two sides is large, the side with small flow rate should adopt multi-pass arrangement to improve the flow rate and heat transfer effect.
3. Generally, when choosing the process, one-way (full parallel connection) is adopted as far as possible, which makes the disassembly and maintenance of the equipment more convenient in use. To adopt multiple processes, the same number of runners is usually arranged in each process.

Choice of flow direction:
The plate heat exchanger is equidistant arrangement, the flow direction of medium can realize full countercurrent, and the maximum average temperature difference can be obtained. Countercurrent and downstream will alternate.

Number of passages:
1. The number of flow passage is affected by the flow velocity between plates, and the selection of flow velocity between plates has a certain range, and is also restricted by the allowable pressure drop.
2. When the flow rate between plates is constant, the number of passages depends on the size of the flow.

Selection of material for plate and seal gasket
1. The selection is based on the physical and chemical characteristics of the medium, mainly considering temperature and corrosion.
2. The thickness of raw material is 0.6-0.8 mm. After pressing into corrugated plate, 25% of the thinning is allowed, so the thinnest part is 0.45-0.6 mm. Therefore, corrosion resistant material is selected.
3. Seal gaskets should be both temperature-resistant and corrosion-resistant. The hardness should generally be 65-90 Shaw hardness. The compression permanent deformation is not more than 10%, the tensile strength is more than 8 MPa, and the elongation is more than 200%.

File for your information: plate heat exchanger pdf.