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Roboze ARGO 500: Saving operating cost by 3D printing shell and tube heat exchangers in Polypropylene

A heat exchanger is a system comprised of certain elements to transfer heat between two or more fluids. Heat exchangers are used in both heating and cooling processes globally across many industries including but not limited to Oil and Gas, Power Plants, Chemical, Fertilizer, Refinery and Petrochemical.

Among the different types on the market, shell and tube heat exchangers allow fluids to absorb or release heat through contact between the surfaces from which they are separated. Depending on the liquids involved, they have metal pipes (generally in carbon steel or stainless steel) inside which a first fluid flows, surrounded by a sealed casing (called mantle) inside which the second fluid flows through the diaphragms. During the heat exchange phase, fluids can move in the same direction or in opposite directions.

Metals have always been considered the most suitable solution to produce these devices due to their high thermal conductivity. However, in certain applications, when aggressive fluids, acids, or bases are present, the problem most frequently encountered is pipe corrosion. Corrosion of heat exchangers has been estimated to generate costs of up to $855 million annually (Willem Faes et al., 2018). These losses are a combination of direct and indirect costs caused by corrosion and can be attributed to several economic consequences (Davis, 2000), such as:

  •  Replacement of corroded equipment;

  • Oversizing to take into account possible corrosion;

  • Preventive maintenance;

  • Plant shutdown;

  • Loss of efficiency (for example, when corroded products decrease the heat transfer rate of the exchanger);

  • Loss of a product (for example, through leaks or contamination of a product).

Moreover, recent studies showed that polymers, e.g., Polypropylene (PP), if particularly thin (with thicknesses below 1 mm), allow a heat exchange comparable to that of metals, while enabling excellent chemical and corrosion resistance (Xiangjie Chen et al., 2016). Using such polymers would be very advantageous from the cost saving standpoint and it also enhances the safety of the operation. In the Figure below, efficiency comparison of heat exchangers based on the thickness is shown.

Heat exchangers that use metal pipes very frequently have particulate deposition, called fouling, a phenomenon that does not occur in those that are made of Polypropylene. Comparing the coefficient of thermal conductivity, in the case of PP it is lower than metals, approximately equal to 0.11 W / (m * K), but the efficiency of the heat exchange increases as the thickness of the walls decreases (as shown in the graph). The value of this coefficient becomes of secondary importance when the fluids involved are highly viscous or corrosive.

PP heat exchangers can generally be subjected to a temperature between 20° C and 80° C (68° F and 176° F) and a maximum operating pressure of 8 bar which depends on the thickness of the walls. This material ensures excellent operating performance with considerable economic savings in applications where these systems are used to transfer heat between corrosive fluids, aqueous, or alkaline saline solutions. In fact, PP heat exchangers are used for cooling sulfuric acid solutions as they represent the most convenient and higher performing solution, when compared to the metal alternative.

3D printing represents an advantageous solution to produce these components. By using PP, it is possible to obtain unprecedented freedom of design, allowing to maximize the heat exchange surface and consequently making the exchanger more efficient.

Today's standards used with traditional methods are:

  • API 660 / ISO 16812 (Shell and Tube heat exchangers for general refinery service).
  • ASME SECT.VIII Div.1 (UHX) or Div.2, PD 5500, EN 13445, AD 2000 Merkblatt.
  • Shell DEP 31.22.20.31 and DEP 31.21.01.30
  • TEMA - Tubular Exchanger Manufacturers Association

Roboze together with the API 20T committee is currently working on the development of a standard for the production of polymeric materials by 3D printing.

Using industrial 3D printing systems, such as Roboze ARGO 500, makes it possible to create large parts for shell and tube heat exchangers. New opportunities for materials selection and using non-metallics such as PP, can provide significant advantages.

To find out all the benefits related to the use of the ARGO 500 and the advantages associated with Roboze Metal Replacement, contact one of our consultants by writing to: info@roboze.com

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