Titanium micro channel porous flow plate appeared around the 1920s and has since found widespread use in many sectors.
The plate heat exchanger consists of a series of parallel plates. They are suitably superimposed allowing the formation of a series of passage channels for the fluids between the plates themselves. The gap created between two adjacent plates constitutes the channel through which the fluid flows.
The holes that allow the entry and exit of fluids
A plate can have dimensions ranging from a few square decimeters (100 mm x 300 mm per side) up to 2 or 3 square meters (1000 mm x 2500 mm per side). The number of plates per exchanger ranges from ten to a few hundred. Thus, reaching exchange areas of up to thousands of square meters.
The trend of the fluids inside the titanium micro channel porous flow plate
The fluids are divided into several parallel streams and can create a perfect counter-current. Generally, these plates are corrugated to increase turbulence. The exchange surface and give mechanical rigidity to the exchanger.
Corrugation is obtained by cold forming of sheet metal with thicknesses from 0.3 to 1 mm.
The most common materials for the plates
The most common materials for the plates are stainless steel, titanium and aluminum. The corrugations present inside the plate impose a tortuous path to the fluid. It defines spacing between two adjacent plates b, which can range from 1 mm to 5 mm.
The fluids can pass through the channels of titanium micro channel porous flow plate in series (rarely common solution). In parallel this creates configurations in countercurrent or co-current. The series configuration is common when there is a small flow rate for each fluid but a high temperature difference.
The high pressure drops and the imperfect counter-current
The configuration with parallel and counter-current channels is common for large flow rates with modest temperature jumps, and is the most common.
There is a high difference between the flow rates (or between the maximum value of the admissible pressure drops) of the two fluids. It is possible to make the fluid with a lower flow rate (or allowing higher losses) travel through the titanium micro channel porous flow plate twice. In order to balance the values of pressure drops or specific flows in the channels.
The different configuration configurations: parallel or series
One of the most important problems for plate heat exchangers is the uneven supply of the different channels in parallel.
In fact, the fluid tends to distribute in greater quantities in the first channels than in the last in order to balance the losses. As the number of plates increases, distribution worsens causing a decrease in the overall performance of the exchanger.
There are two basic types of titanium micro channel porous flow plate:
- Brazed (BPHE-Brazed Plate Heat Exchanger)
- Gasket (PHE-Plate Heat Exchanger).
Gasketed plate heat exchanger
In the PHE the plates pressure pack by means of heads and tie rods. The tightness guarantees the gaskets. The gaskets, in addition to the seal, are common to direct the fluids.
The gaskets are common along the grooves on the edges of the plates. The maximum operating temperatures of the gasket exchangers are between 80 ° C and 200 ° C. The pressures can reach 25 bars. The gaskets are available in various types of butyl or silicone rubbers.
Main characteristics of titanium micro channel porous flow plate
The main characteristics of these types of exchangers are:
- Easy and quick disassembly for cleaning and checking operations
- Adaptation to variable conditions of use by adding or removing thermal plates to modify the installed thermal flow
- Fluid leaks due to imperfect sealing of the gaskets do not contaminate the other fluid but go towards the outside
- Possibility of using materials that do not adapt well to welding, such as titanium - the gaskets limit the pressure values and maximum temperature
- High costs due to the design of molds, presses and the entire production process
- High costs of gaskets
Brazed plate heat exchangers
The brazed plate heat exchangers do not have heads, tie rods and seals. The titanium micro channel porous flow plate brazes in the oven at temperatures of the order of 1000 ° C.
During the assembly phase, a sheet of brazing material (generally copper but also nickel) place between the plates. The pack presses and then place in the oven for a few hours. The porous flow plate exchanger is more compact, lighter and less bulky than one with gaskets.
The path made by the hot and cold fluid
The brazing therefore fulfills both the function of the gaskets and that of the frame. In these exchangers, plates with herringbone corrugations are generally common. They assemble by alternating the directions of the corrugations in order to create the contact grating.
The crossing points between the corrugations of two coupled titanium micro channel porous flow plate form a dense network of contact points. It gives the pressure seal and induces swirling flows that improve heat exchange.
In this way the turbulence of the fluids is high even for low nominal inlet speeds and the outflow changes from laminar to turbulent for low specific flow rates.
Comparison of different heat exchangers
The actual area is difficult to calculate so to compare different heat exchangers we refer to the projected area.
It should be borne in mind that exchangers with the same projected area (i.e. plates of the same size) can have different effective areas depending on the value of the increase factor φ.
Conclusion
The ratio of plate length L to width W also affects performance but to a lesser extent than other variables. In general, a high ratio between length and width of the plate gives titanium micro channel porous flow plate coefficients but higher pressure drops.
To buy best porous flow plate you can order in bilk at Stollpche. We are the leading manufacturers of heat exchangers in China.
