Design of Recuperative Heat Exchanger Presented by -- Jinying Zhu

Review: On June 05, we visited AMERICAN TECHINCAL CERAMICS, and got some punch samples. We also took some microscope pictures, and the pictures showed good punching quality. The Engineer from ATC recommend that the transition layer should use metal instead of LTCC because these patterns are very difficult to achieve and the channels might be blocked when LTCC is vitrified due to the support structure. At the same time, it is also difficult to align the transition layers.

Modification in structure: Metal can not be used to build the header due to high thermal stress. If the effectiveness is as high as we expect, it is a good alternative to choose circular ducts. We redesign the recuperator by considering the thermal effectiveness and manufacturability. The layer patterns for main part are changed as follows. Blue color: cold channels Red color: hot channels

Modification in structure: The structure will improve the effectiveness slightly. We carried out the thermal calculations for both 100 micron square duct and 100 micron circular duct, the effectiveness is % and 98.24% respectively. Xiaoyi performed the 3-D numerical simulation by using FLUENT, and her result also verified this. The structure are manufacture favor: We don’t need transition layers. Mechanical stress is not an difficult issue any more, which means that the support structure is not required. The locations of maximum stress are at the corner of side wall, which can be settled simply by increasing the thickness of side wall. Different sizes of circle punches are available at ATC, we don’t need to order special punch.

Consideration and calculation result: LTCC (Dupont 951) will shrink uniformly when fired, and the shrinkage is 12.7%. ATC has 100 micron, 150 micron, 200 micron circular punches. We choose 150 micron diameter ducts. The diameter will be about 120 micron after the material is fired. dT (K) T cold side out (K) T hot side out (K) efficiency (%)

Consideration and calculation result:

Finished work and future work: Visited ATC second time and had a meeting with the Special Projects Coordinator and the Business Development Manager on July 16. Showed them our 3-D feature mold, the Coordinator confirmed it is doable. It is necessary to build a small sample first due to the lack of experience of such large feature in the field of LTCC technique. Dimension drawings is ready to send out to ATC. ATC will approve these drawings within July 31.

Future measurement: Temperature: T-h,in; T-c,in; T-h,out; T-c,out Differential pressure: ΔP c, ΔP h Pressure: P h,in, P c,out Leakage: hot →cold, cold→hot Mass flow: c, h, both to be measured at the hot end.