The passage of a fluid through a porous medium typically results in the transfer of heat between the fluid and the medium. If the porous medium contains more heat than the fluid, it will be cooled by the transpiration of the fluid through the porous structure. In some applications, this effect may be useful when a particular component tends to overheat.

Dynapore® diffusion-bonded porous metal structures offer a matrix with high internal surface area and controlled permeability to flow. If a particular component is fabricated from a suitably selected Dynapore® material, the component may become "self-cooling" in the context of the application.

As an example, in liquid hydrogen/oxygen rocket engines, the hydrogen fuel injector nozzles may be embedded in a flat solid plate. The nozzles may have a tendency to overheat and melt. By substituting a high-strength controlled permeability Dynapore® material for the solid plate, a pre-determined percentage of the hydrogen may be permitted to flow through the plate itself, with the balance flowing through the injector nozzles. The plate is cooled by the transpiring flow of hydrogen through its internal void volume. The cooled plate in turn becomes a heat sink and prevents the nozzles from melting.

Other applications for transpiration-cooled components have included combustion chamber and afterburner liners, as well as turbine blades. The success of these applications depends on the ability to produce a medium with controlled permeability in accordance with engineering requirements. MKI Dynapore® has been successfully deployed in a variety of such scenarios.

The Perfect Media for Transpiration Cooling Applications

In severely heated components, transpiration cooling allows a fluidic coolant that flows through the surface and exits the component from the heated surface through small pores in the component. Dynapore® is perfect for this application for many reasons:

• Excellent formability - new components fabricated with Dynapore® can replace obsolete components.
• Porosity & permeabilty control - Dynapore® can be made to allow a specific transpiring flow rate to control cooling characteristics of the component.
• Mechanical strength & corrosion-resistance - all standard Dynapore® parts are made with high-grade stainless steel, making the new components very durable and be able to stand up against operating environments.

After passing through the Dynapore®, the coolant will both remove heat from the surface and reduce the convective part of any heating very efficiently. Some commerical turbine parts and rocket engines presently use transpiration cooling. Consult the factory today and find out how we can solve your cooling needs with Dynapore®.