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30/01/15 The fourth ARCHER Newsletter was released on 30 January 2015. Read online here

21/01/15 The second ARCHER EUROCOURSE, hosted by NRG, was held in Petten from 19-20 January 2015. Click here for more info

26/11/14 The third ARCHER Newsletter was released on 26 November 2014. Read online here

28/10/14 The ARCHER final meeting was held on 21-22 Jan 2015 at NRG in Petten (NL).

27/10/14 The High Temperature Reactor (HTR) Conference was held from 27-31 October 2014 in Weihai, Shandong Province, China. Click here for more info

29/03/14 The second Newsletter was released on 28 March 2014. Read online here

Supported by

European Commission

Compact Intermediate Heat Exchanger (IHX)

The effective transfer of heat is an important requirement for the High Temperature Reactor (HTR). For higher temperature exchanges, the gas-to-gas IHX is likely to offer a cheaper, more robust and compact solution.  Temperatures are close to the core outlet temperature for most of its lifetime, which requires considerable design development to achieve a solution capable of resisting to such temperatures for long periods of time.

The Plate Stamped Heat Exchanger (PSHE) design offers the most promising solution.  This design of a compact IHX is being investigated in the ARCHER project, under WP43. The work involves the design, analysis and testing of an IHX mock-up in the CLAIRE Loop at CEA.

PHEs were formerly used to pasteurise milk in the liquid food industry. Their dismantling capabilities, high heat transfer coefficients, and short and well-defined fluid path length meant that it gradually became the standard choice. In terms of technology, PHEs were made up of a pack of corrugated plates pressed together.

Plate sizes ranged from 0.02 m2 to over 3 m2 with conventional pressing, and up to 15 m2 for explosion formed plates.  Hydraulic diameters were between 2 and 10 mm for most common plates. Typically, the number of plates ranged from 10-100, giving 5-50 channels per fluid.

CEA launched a study with Alfa Laval to check the potential of this technology and provided promising results in terms of CFD simulation, and mechanical and technology studies. The partnership was expanded to include AREVA and other partners.

The PSHE comprises a stack of corrugated plates generating mechanical contact points between the plates. However, it is necessary to apply external pressure to ensure the rigidity of the system. Depending on the application, the plates are mechanically maintained by tied bars or by an external pressure higher than that of the fluids.

Following an initial phase of sizing and definition of the depth of stamping, angle of corrugation and shape, more detailed studies were undertaken to check the thermo-mechanical behaviour and to improve it as far as possible.

The mechanical study led to the optimisation of numbers, thickness and width of the plates.  Depending on the considered case, parts of the IHX underwent tension, compression or bending stresses; the highest damage effect was used to size the component.

Iterative sizing and CFD/FEM calculation were performed to minimise the thermo-mechanical stresses under steady and transient conditions so that the length and the height were chosen to give smooth thermal gradients.  The technology task involved exploring different types of welding processes (laser, plasma, diffusion bonding, etc.) and an important challenge was to set the welding parameters and complete welding tests on single and stacked plates to validate their application.

All of this work has led to experimental focus and tests within ARCHER. Special care was given to size the mock-up in order for it to fit the test rig, check its industrial feasibility, keep the same plate size as a real IHX, adapt the number of plates so that thermal and hydraulic laws can be expressed in a suitable range of Reynolds number and carry out long-term air tests at nominal He-He IHX.

The air inlet temperature was increased by 50°C to accelerate thermal damage. Thermal shocks were generated to match as close as possible to those of the real IHX (fatigue tests).  Material tests were also performed to check strength and durability.

The IHX mock-up has now been manufactured and is currently housed in the CLAIRE Loop for testing, which will begin shortly.

The mock-up was made with Alloy 800H material and has the same size as a real IHX module with fewer plates, 20 instead of 300. Welding and machining processes have been optimised to ensure the quality of the component.

This has been a significant achievement for all concerned and it is expected that the work in ARCHER will be an important milestone in ensuring that this technology is available for the HTR demonstrator.