Plate heat exchanger is a new type of high-efficiency heat exchanger made of series metal sheets with corrugated shape. During various plates have thin rectangular channels , and exchange heat through the plates.
Plate heat exchanger is an ideal equipment for liquid-liquid and liquid-steam heat exchange. It has the features like: high heat exchange efficiency, small heat loss, compact and light structure, small footprint, easy installation and cleaning, wide application, and long service life, etc.
Today we will talk more knowledge about plate heat exchanger.
Structure
Main components: Seal gasket, fix plate, active plate, screw, upper column, lower column, support rod , frame plate, etc.
Plate heat exchanger has 2 types: frame type (detachable) and brazing type, meanwhile there are 2 types of plates: corrugated plate and round-shaped plate.
Functions of Plate Texture
It will cause fluid turbulence, enhances heat transfer, and the corrugations of adjacent plates form contact resistance points, improve pressure resistance.
Chocolate distribution area
Make the fluid flow evenly across the entire plate, with the same pressure drop at “A” and “B”, minimize the pressure loss, increase effective heat transfer, and allow parallel flow.
The plate heat exchanger consists of a group of plates stacked into a channel-shaped plate package. The two ends have bottom plates with pipe connections. The whole plate is made by vacuum brazing.
Two media flow in adjacent channels respectively. The plates between adjacent channels are pressed into corrugated shape to enhance the heat exchange between the two media. In the brazed plate heat exchanger for refrigeration, there is always one more water flow channel than refrigerant flow channel.
Above is single-side flow schema, some heat exchangers are made for diagonal flow, means “Q1” and “Q3” contain one medium, while “Q2” and “Q4” contain another medium.
The fastening way is screw and bolt structure, which is convenient for on-site disassembly and repair.
Working Principle
The plates of plate heat exchanger are sealed and guided by sealing gaskets to separate the cold/hot fluid channels. The cold/hot heat exchange medium flows through their respective channels and exchanges heat with the separated plates to achieve the set temperature.
Each plate has openings at the four corners, then form to distribution pipeline and collection pipeline, after being assembled into a plate pack. After the heat exchange of the cold/hot medium, it flows back from the respective collection pipes then recycle.
Single-flow structure: only two plates don’t exchange heat – front (first) and bottom (last) plates.
Double-flow structure: Each flow has 3 plates without heat exchange.
Plate Material
| Plate material | Material series number | Suitable medium |
|---|---|---|
| Stainless steel | 304, 316,316L | Clean water, river water, cooking oil, mineral oil |
| Titanium and Titanium Palladium | Ti, Ti-Pd | Seawater, brine, saline solution |
| Nickel | Ni | High temperature, high concentration caustic soda |
| Hastelloy | Hastelloy | Concentrated sulfuric acid, hydrochloric acid, phosphoric acid |
| Special steel | SM0254, 20Cr, 18Ni | Dilute sulfuric acid, diluted salt aqueous solution, inorganic aqueous solution |
Gasket
Gaskets used as sealing elements between heat exchanger plates to prevent leakage. In HVAC industry, gaskets are mainly rubber products, which are greatly affected by temperature and medium.
Gasket requirement:
Anti-aging, tear-resistant, high resilience
Sealing contact surface is accurate in size and the alarm signal hole is sensitive
Adhesive-free structure, easy to disassemble and assemble
Gasket selection:
According to the medium features
| Gasket material | Material code number | Temperature | Suitable medium |
|---|---|---|---|
| Nitrile Butadiene Rubber | NBR | -15 ~ +120 °C | Water, sea water, brine, mineral oil |
| Nitrile Butadiene Rubber + | HNBR | -15 ~ +140 °C | High temperature mineral oil, hot water |
| Ethylene Propylene Diene Monomer | EPDM | -25 ~ +150 °C | High temperature water, acid, alkali |
| Ethylene Propylene Diene Monomer + | HEPDM | -25 ~ +170 °C | Water vapor, acid, alkali |
HVACR Industry Application
– District heating system
– District cooling system
– Heat and power system
– Geothermal water heating system
– Instant domestic hot water system
– Swimming pool constant temperature system
– Solar water heating system
– Air conditioning system
– Cooling Tower
– Groundwater cool/heat source system
– Heat recovery system
– Ice storage system
– Ceiling cooling system
Installation
Upside down installation
Some plate heat exchangers can place upside down, please confirm with the supplier.
Installation posture
Must install vertically, not horizontally.
Installation “1” is correct, “2” and “3” is also ok, “4” is wrong.
Pipeline layout
Don’t allow vibration and pipe thermal expansion to reach the plate heat exchanger.
Actions:
– Add rubber gaskets between BPHE (brazed plate heat exchanger) and the bracket.
– Use vibration dampers for the compressor.
– Use bellow or other vibration absorb device when the straight pipe section is long. A return bend higher than the inlet pipe can make the water fill the BPHE (see above picture).
Pipeline welding
Clean and degrease the welding surface with solvent. To avoid oxidation and cool the BPHE, blow nitrogen through the welded pipes. Keep water flowing in the water-side pipeline.
Keep water flowing before welding starts and keep it flowing until the BPHE can be touched by hand.
The solder should contain at least 45% silver and brazing should be carried out at less than 650 ℃. In any case, the weldment shouldn’t exceed 800 ℃.
TIG (Tungsten Inert Gas Shielded Arc Welding) is the least-heat released welding method.
BPHE Leakage Checklist
System check
– Check shutdown sequence and evaporation temperature
– Check if vibrations from other devices
– Is an electric valve or solenoid valve applied on the water side?
– Does the water contain excess chloride ions or other corrosive agents?
External check
– Is there a bulge on the back cover opposite the water inlet?
– Are there any signs of deformation on either side?
– Are the pipe connections tight?
– Check the appearance for any damage during transportation or installation?
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