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Design of Recuperative Heat Exchanger

Design of Recuperative Heat Exchanger. Presented by -- Jinying Zhu. Review:. The material: LTCC (may use Dupont 951) Properties:. - Flexural Strength: 320 MPa - Young’s Modulus: 152 GPa - Thermal Conductivity: 3 W/mK. The size of recuperative heat exchanger. - about 8cm×8cm×25cm.

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Design of Recuperative Heat Exchanger

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  1. Design of Recuperative Heat Exchanger Presented by -- Jinying Zhu

  2. Review: • The material: LTCC (may use Dupont 951) • Properties: - Flexural Strength: 320 MPa - Young’s Modulus: 152 GPa - Thermal Conductivity: 3 W/mK • The size of recuperative heat exchanger - about 8cm×8cm×25cm

  3. Review: • Thermal calculation result: Thermal conductivity Length T (cold side out) T(hot side out) effectiveness 3 W/mK 25cm 296.96 K 78.036 K 97.8% • Structural calculation result: Material flexural strength Thickness max. stress max. displacement (MPa) (μm) (MPa) (μm) 951 320 200 215 2.95

  4. The bonding concept for LTCC: • 700 °C --- transition temperature of glass • 800 °C --- the glass begin to flow and surround the grains of ceramic, joining them together • 850 °C ---the glass will completely surround the grains and bond them strongly

  5. The bonding concept for LTCC:

  6. Problems and shortcoming: • It is difficult for the vapor produced during heating to escape • It is difficult to heat the recuperator uniformly because of the large size • The wall thickness was chosen to be 200 μm because of the high differential pressure of JT - This maybe unnecessary • Axial heat conduction is playing an important role for the 200 μm wall

  7. Problems and shortcoming: Temperature along the length for 200μm wall thickness

  8. Solution: It is very important to reduce axial conduction. To reduce the axial conduction: • Wall thickness: 50μm (using thinner wall will also reduce the size of the recuperator) • Δp: 4 bars (lower due to the lower differential pressure of the centrifugal compressor) To reduce the size: • Grid number: 100×100 • Size: about 2.5cm × 2.5cm × 8cm

  9. Calculation results: Structural calculation: -- Max. stress: 200 MPa -- Max. displacement: 5.02 μm Thermal calculation: dT (K) T cold side out (K) T hot side out (K) efficiency (%) 5.818 78.818 296.18 97.459

  10. Calculation results: Temperature along the length:

  11. Future Work: • To confirm the validity of structure design • To work with Dr. An in fabricating the LTCC recuperator

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