Ceramic/Metallic Heat Exchanger Development

9th Annual SECA WorkshopPittsburgh, PA.August 7, 2008

Anthony F. Litka

Project Objective

Combine ceramic and metallic heat exchanger cores to produce a low cost, high effectiveness, recuperator for cathode air preheating

Hybrid Recuperator Advantages

M etallicAdvantages

• M anufacturability• Extended Surface• Compactness• Therm al Shock

Disadvantages

• H igh Cost• Fouling/O xidation

C eram ic

Advantages

• Low Cost M aterials• H igh Tem p Stability• Single Casting

Disadvantages

• Therm al Shock

H ybridAdvantages

• Low Cost M aterials Throughout• M odular M anufacture• Temperature G radients on Ceram ic are R educed• M aterials O ptimized for Temperature• Therm al Expansion Unrestrained

Recuperator Specification

• Exhaust Inlet Temperature – 850 – 950 C• Air Outlet Temperature – 725 - 800 C• Effectiveness – >85%• Total Pressure Drop – 1250 Pa• Equal Air and Exhaust Flowrates• Air Flow – 150 lpm per kWe

Initial Generator Configuration

Cathode Air Path

Burner

Exhaust

SOFC Stacks

Cathode Blower

Recuperator

Cathode Air Path

Burner

Exhaust

SOFC Stacks

Cathode Blower

Recuperator

Cross Flow Metallic Recuperator

CathodeAir InHot Air

Out

ExhaustIn

ExhaustOut

CeramicCore

MetallicCores

CathodeAir InHot Air

Out

ExhaustIn

ExhaustOut

CeramicCore

MetallicCores

Cross Flow Hybrid Recuperator Concept

Ceramic Core

Manufactured by Blasch Precision Ceramics , Albany NY

Cross Flow Configuration

3 Pass Cross Flow Hybrid Performance

Metallic Core Effectiveness = 77.3%

Metallic CoreEffectiveness = 77%

Ceramic CoreEffectiveness = 37.7%

Air Inlet

Air Outlet

Exhaust Inlet

Exhaust Outlet

T = 417 C

T = 641 C T = 708 C

T = 532 C

T = 845 C

T = 25 C

T = 718 C

Flow = 70.9 kg/hr

Flow = 67 kg/hr Overall Effectiveness = 85%

2 Pass Cross Flow Hybrid Performance

Metallic Core Effectiveness = 78.7%

Ceramic CoreEffectiveness = 47%

Air Inlet

Air Outlet

Exhaust Inlet

Exhaust Outlet

T = 538 C

T = 850 C

T = 677 C

T = 23.5 C

T = 684 C

Flow = 70.9 kg/hr

Flow = 70.9 kg/hr

Overall Effectiveness = 80%

Stack Size Reduction

Cathode Air Downcomer

Offgas Injectors

Fuel Plenum

Offgas Plenum

Cathode Air Distribution Region

CatyliticOxidation Tile

Cathode Air to and from Recuperator

Anode Gas Inlet

Cathode Air Downcomer

Offgas Injectors

Fuel Plenum

Offgas Plenum

Cathode Air Distribution Region

CatyliticOxidation Tile

Cathode Air to and from Recuperator

Anode Gas Inlet

Axial Flow Stack Geometry

Counter Flow Recuperator

Startup Burner

Exhaust Plenum

Air OutletPlenum

Stack Chamber(cells not shown)

Hot AirDuct to StackBottom

Air InletPlenumAir (tube side)

Exhaust (shell side)

Counterflow Fin Core Recuperator

Counter Flow Hybrid Recuperator

Recuperator Assembly

Ceramic Monolith

Fin Core Hybrid Cross/Ctr Flow

Ceramic Core Performance

500

550

600

650

700

750

800

850

350 400 450 500 550 600 650 700 750 800 850

Ceramic Air Inlet Temperature (C)

Cer

amic

Air

Out

let T

empe

ratu

re (C

)

Exhaust Inlet Temperature = 830 CAir & Exhaust Flow = 200 lpm

Model Prediction(Baseline)

Model Prediction(Reduced Channel Width)

Folded Sheet Recuperator

Folded Sht Hybrid Performance Gain

Air Flowlpm Metallic Hybrid100 0.71 0.787200 0.705 0.816300 0.698 0.780

Ovl Effectiveness

Cross/Ctr HX Performance

0

10

20

30

40

50

60

70

80

90

100

350 450 550 650 750 850 950Exhaust Inlet Temp (C)

Air

Tem

pera

ture

Del

ta C

eram

ic (C

)

100 LPM

200 LPM

300 LPM

Future Activities

• Complete performance testing• Conduct both long term and thermal cycle

testing• Evaluate techniques to optimize ceramic

core heat transfer – more passages, fins• Evaluate and demonstrate heat exchanger

geometry to larger sizes