Differences in construction and production of radiators

Differences in construction and production of radiators

Radiator The car, as mentioned, consists of three parts: the core (network), the inlet and outlet collectors (inlet and outlet tanks) and the expansion source. One of the most important current differences between brass and aluminum copper radiators is the difference in the method of making the core (grid).

The core (radiator) usually consists of three main parts:

  • Tube
  • Fin
  • Tube sheet / Header

And a sub-section called Side

How to connect the pipe to the blade and the pipe to the header is the main issue in the production of radiators. At present, brass copper radiators are produced using the conventional soldering method (Soldering) and aluminum radiators are produced using the Brazing method or mechanical connection.

Making method with soldering technology (Soldering) :

Soldering is the joining of two solid materials together using the third material, which has a lower melting point than the first two materials and easily adheres to both materials. In this process, the filler material reaches the melting point and moves as a melt between two solids with the help of flux and when it cools, it sticks to both materials and is solid at the temperature used. In the production of brass copper radiators, pipes, fins and headers are made of copper and brass alloy and the filler material is tin and lead alloy. The tin and lead alloy used has a melting temperature of 430-380 degrees Celsius (usually 75% -70% tin and 30% -25% lead) higher lead content and some silver in the alloy composition (none of the radiator manufacturing companies in Iran They do not use silver) enhances the mechanical properties of the solder but the higher the amount of lead in the solder, makes soldering difficult. The fluxes used in the soldering process are zinc or inorganic chloride (the remaining flux in the soldering process causes problems. Corrosion).

Soldering is done in various ways. In immersion soldering, the complete assembled assembly is cleaned and inserted into the flux pan, then the assembly is inserted into a plant full of molten solder, resulting in a simultaneous connection between the individual blades and the pipes and Headers are established.

In the non-immersion method, the whole assembled set is placed in a flux pan or soaked in a flux sprayer and then placed in a baking oven, usually for 5 minutes (depending on the type of grid) at a temperature of 400-350 ° C until Tin solder on the surface of brass pipes causes sealing in the pipe (in rivet pipes) and connection to copper blades and headers (of course, the pipes protruding from the header re-enter the molten solder (dip) in the dipping device to the connection of the pipe to the header. More strength (cores) The cores (grids) produced by the soldering method have low strength and are not suitable for structural applications and temperatures above 100 degrees.

As mentioned, aluminum radiators are produced in two ways: expansion (expansion joint) and brazing (metallurgical connection) and based on this, there are two types of aluminum radiators.

Radiator with mechanical connection (Expand):

In this method, the cross section of the pipes is round or elliptical. The pipes are made by extrusion or tension method. In the production of this type of radiators, the blades are produced by a fin machine, which in addition to the blades

Louvres (these are small appendages that create air ducts at the blade surface). It should be noted that these ducts are blocked by dust, and when the louvers are blocked, the efficiency of the radiator decreases and the pressure drop on the air side increases and the radiator fan discharge increases. It is reduced and as a result the amount of heat transfer is reduced again (pipe passage is installed) In the assembly of the radiator network, first the pipes pass through the vane holes and by special appointments for connecting the pipe to the vane by expanding or widening the wall The pipe is glued to the outer surface of the pipe to the vane, then the pipes are connected to the header, and finally the washers are sealed to the pipes by special washers or epoxies, which are cheap to produce, but due to geometry limitations. These radiators are less effective in design. They are mostly used in engines with low displacement and without additional load, such as air conditioners. Regarding the metallurgical connection a The set value of this resistor is approximately 20% of the total thermal resistance. Metallurgical joints are much better than expansion joints (mechanical) and therefore the resulting resistance is generally ignored.

Radiator with brazing connection:

In this method, the aluminum strip (Almn Group 3000) from which the pipe is to be made is inserted into the roll forming machine and rolled, then its seam is welded by High Frequency technology. An aluminum radiator is coated on one side of a strip of aluminum alloy (4047/4045/4043) that has a lower melting temperature than the aluminum used to make the strip, which is called a clad. This action causes the coating to melt when it reaches freezing temperature, leading to the filling of pores and the formation of suitable uniform connections. The fins are made of Almn Group 3003 or Almgsi Group 6000, and the headers are made of one of these alloys. There are two groups. The blades are not coated and are made of corrugated blade (Corrugate) by a blade machine and a Louver is created on them, then it is placed in the jig assembly machine of pipes and blades and then the headers are installed and finally the network is assembled and finally Stainless steel C-frame or U-frame jigs are assembled to prevent the network from breaking and the more attractive connection of pipes and fins to each other is installed in the network and then fluxed (flux solution: water + 15 - 15% water volume, flux material And then enters the preheating part of the furnace and finally enters the furnace and at the brazing temperature (about 600 degrees Celsius) the brazing operation is performed. The total elapsed time of the preheating operation, pouring and then reducing the temperature of the part is about 30-25 minutes, but the time required for pouring is only 12-8 minutes (depending on the type of network and its dimensions). At present, vacuum brazing, dry air with chloride flux and Nocolok non-corrosive flux are mostly used in vacuum / shielding gas conditions, which requires vacuum / shielding gas in non-clad aluminum. It is not, but the flux is corrosive, the excess of which must be removed and the network washed with acidic solutions and water.

Compiled and summarized by: Engineer Hamid Sadeghi

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