Design of a plate heat exchanger

Construction of a plate heat exchanger: a guiding beam and a supporting base are fixed between the frame and the stationary steel plate, forming a rigid frame structure.

The heat exchange surface consists of a set of corrugated stainless steel plates assembled in a block that is mounted in the stationary frame of the unit. The package consists of identical plates on a supporting base. Each plate is installed by rotating it 180° relative to the previous one, forming channels in the shape of a mirror sine wave for the passage of the heat transfer medium.

There are four holes in the corners of the plates that, when assembled into a block, form four collectors for the passage of the heating and heated media. Two holes in the plate perform a transit function, one performs a distribution function, and one is a collection collector.

The polymer seal is attached to the clamps around the perimeter of the plates, preventing leakage in the gaps between the plates and the transfer of the heating medium from the heating to the heated circuit.

The end plates in the package do not participate in the heat transfer process. In single-pass heat exchangers, the last plate is made 'blind' (without holes).

The block of plates is fixed with a movable pressing plate using tightening bolts, one end of which is attached to a bearing in the stationary pressing plate and the other in the movable pressing plate.

The assembled plate heat exchanger is installed on a foundation, secured with bolts through the holes in the support feet of the frame and the steel plate.

Plates

The key element in the design of a plate heat exchanger is produced by cold forming on a hydraulic press from sheet metal with subsequent electrochemical polishing.

The plates are stamped to a depth of 2.5 to 4 mm from alloyed stainless steels and titanium alloys depending on the temperature regime of operation, pressure, and chemical properties of the working fluids. The most common starting materials for plates are: AISI 304, AISI 316, SMO 254, Titanium.

The thickness of the plates varies in the range of 0.4 to 1 mm. Thin plates are less expensive and have higher thermal conductivity, but are designed for lower pressure and shorter service life. The standard plate for heat exchangers installed in heating and hot water supply systems is a plate made of AISI 316 alloyed stainless steel with a thickness of 0.5 mm.

The relief of the plates performs the function of uniform distribution of the flow over the surface, provides rigidity of the plate structure, and forms a spiral flow that promotes self-cleaning of the channels of the heat exchanger.

The angle of formation of the plate relief affects the speed of the working fluid layer and turbulence, which leads to changes in the heat transfer characteristics of the heat exchange apparatus.

H type - thermodynamically long profile - a heat exchanger with [H] configuration plates is characterized by a high heat transfer coefficient and an increased pressure drop. High flow turbulence promotes self-cleaning of the heat exchanger from scale deposits.

L type - thermodynamically short channel - plates with an L-pattern have a lower heat transfer coefficient, significantly lower pressure drop during flow passage, and become dirty faster compared to H-plates.

M type - mixed channel - obtained by overlaying H and L profiles, inheriting the average values of heat transfer and pressure drop.

Polymer Seals

They perform a sealing function in the gaps between the plates, as well as prevent mixing of the heated and heated water.

Elastomers are made in the form of a solid polymer gasket (EPDM, NBR or FKM). The seal is attached to the contour of the heat exchanger plate in a special groove using epoxy adhesive or clips provided for in the gasket. Fixing the elastomers on the clips allows for quick replacement during maintenance.

EPDM seals are used in heating and hot water supply systems.

The average service life of polymer seals in a plate heat exchanger is about 8 years.