High-Temperature/High-Pressure Heat Exchangers:
Microtubes are inherently useful in high-pressure applications: microtubes constrain high pressure fluids efficiently and the high heat transfer/volume ratio associated with small scale passages means that the size/cost of the heat exchange is reduced. The availability of superalloy microtubing (such as Inconel 625 and Haynes 282) means that the advantages of microtubes in high pressure applications can extend to high temperatures.
An example of a high temperature/high pressure currently being designed by Mezzo is a 5 MW supercritical CO 2 recuperator. This heat exchanger is being designed as part of an ARPA-E project. The characteristic temperature and pressure of this heat exchanger is 800 0 C and 3750 psi, respectively.
5 MW CO 2 recuperator core specifications:
Diameter= 200 mm
Core length = 1400 mm
Core (tube) mass = 34 kg
Regenerators for Reverse Brayton Cycle (Cryocooler application):
The Reverse Brayton Cycle incorporates a recuperator that must provide extremely high effectiveness (on the order of 99.8%) and low pressure drops (1% of full-scale absolute pressure of each fluid). Mezzo- along with Creare, Inc.- co-developed a microtube recuperator that provides the needed performance while being more affordable than competing designs.
Phase Change Material (PCM) Heat Exchangers:
Mezzo has manufactured PCM heat exchangers that provide weight savings and possible advantages with respect to mitigating stresses induced during the freezing/melting cycle associated with energy storage and release. Microtubes are advantageous because a relatively spare array of tubes will provide a short conductive length scale that ensures a minimum thermal resistance between the entire volume of PCM and the fluid that alternates between freezing and melting the PCM. The sparse array of tubes means that core mass is reduced and the volume fraction of the core associated with the PCM is maximized.
Polymer Heat Exchangers:
Mezzo manufactures polymer tube heat exchangers that provide an extremely lightweight product useful for aerospace applications (particularly the UAV industry). Polymer microtube heat exchangers often provide almost equal thermal performance to otherwise identical metal microtube products that Mezzo manufactures (the thermal resistance through the tube wall is not significant regardless of the choice of tube wall material).
Condensers and Evaporators:
Microtube condensers and evaporators can be fabricated from a variety of shapes and provide compact, high performance solutions when volume and weight are of importance. Thermal models to predict the thermal performance of microtube products involving phase change are inherently much more complex than models involving no phase change. Despite this fact, Mezzo is able to combine its empirical database of past products involving phase change with continuously improving models to provide high performance condensers and evaporators that meet the needs of the customer.
Exhaust Gas Coolers (EGRs):
Mezzo has designed an Exhaust Gas Cooler that is considerably lighter and more compact than conventional EGR coolers. Despite being compact, the flow passages are large enough to prevent fouling. The Mezzo EGR gas cooler is another example where Mezzo products can function in harsh and dirty environments.