Selection Plate and Frame Heat Exchanger I

Selection Plate and Frame Heat Exchanger I

19 Mar 2019

Selection of type of plate heat exchanger:

There are many kinds of plate heat exchangers, each of which has its own working condition.In engineering design, this should be the first choice.
If temperature is above 200 ℃, pressure is greater than 2 mpa, soldering heat exchanger can be selected.Iif the area is larger, can also choose all the welding heat exchanger;

If temperature is greater than 300 ℃, pressure is greater than 3.5 MPa, you should choose plate and shell heat exchanger;
For the condition of small temperature difference at the end, shallow groove ripples can be selected. For frequent disassembly, removable heat exchanger can be selected;
For those with large flow difference, asymmetric heat exchanger can be used.

Select version:
Main consideration of the heat transfer effect and pressure drop requirements:
If the pressure requirement is above 1.2mpa, herringbone ripples will be selected in most cases.
If the pressure drop requirements are small and the heat transfer effect requirements are not high, flat ripples can be selected;
If more impurities in the medium, spherical ripples can be selected;
For the pressure drop and heat transfer effect,there are certain requirements, the hot mixed plate can be selected.

Single chip area selection:
Choose reasonable single - chip area and it can avoid the situations when total plates are too many or too few.
Too many plates will make the equipment cover too much area;
Too little may increase the number of processes and increase the pressure drop;
At the same time, the size of the single chip area is also related to the size of the corner hole to some extent, which directly affects the change of flow rate and velocity.

Selection of flow velocity:
The flow velocity on the main stream line is about 4-5 times of the average flow velocity.
Under normal circumstances, the selection range of flow velocity between plates is 0.2 ~1.0m/s,
When the pressure drop is allowable, the maximum value is taken to obtain better heat transfer effect, so as to reduce the heat transfer area.

Process selection:
When the plate is symmetrical and the flow rate of hot and cold medium is equal, equidistant arrangement should be adopted to make the medium flow direction full counter-current;
When there is a big difference in the flow rate between the two sides, the side with small flow rate should adopt multi-path layout to improve the flow rate and enhance the heat transfer effect;
In general, in the selection of the process, as far as possible to use one-way (full parallel), so that the equipment in the use of disassembly and maintenance are more convenient. If multiple processes are used, the same number of channels is usually arranged in each process.

Selection of flow direction:
The heat exchanger is equidistant arrangement, the flow direction of medium can realize full countercurrent, to obtain the maximum average temperature difference
When the two sides are not equal, the reverse flow and the downstream flow will occur alternately.

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

Selection of sheet and sealing materials:
According to the physical and chemical properties of the medium and the main consideration is temperature and corrosion.
The thickness of the plate is 0.6-0.8mm, and 25% reduction is allowed after the corrugated plate is pressed. Therefore, the thinnest part is 0.45-0.6mm, so corrosion resistant materials are selected.

Sealing gasket should be resistant to both temperature and corrosion, the hardness should be generally in 65~90 shore hardness, compression permanent deformation of no more than 10%, tensile strength 8MPa and elongation 200%.