template design © 2008 stress analysis with small deformation has been performed to obtain the...
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TEMPLATE DESIGN © 2008
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• Stress analysis with small deformation has been performed to obtain the stress field due to pressure and temperature fields. OpenFOAM has been used as the platform for simulations.
• That maximum value of Wall Shear Stress was 9.2Pa and occurred at tips of the pulmonary valve [3].
a) b)
Figure 7. WSS magnitude: a) entire fluid contact surfaces, and b) cut-away enlarged view of higher shear stresses region.
A 3-D high resolution human heart geometry extracted from CT-angio data was used for this research [2].
a) b)
Figure 2. Heart model: a) whole heart and b) innermost contact and outermost surfaces.
Separate surfaces to define different computational domains and apply different boundary conditions.
a) b) c) d)
Figure 3. Heart’s surfaces: a) sagittal view, b) outermost surfaces in red, c) right (pulmonic) heart circulation domain in green, d) left (systemic) heart circulation domain in blue.
Heart Transplantation
Contact Information
Florida International UniversityMAIDROC (Room EC2960)10555 West Flagler St.MIAMI, FL 33174 - USA
PHONE: (305) 300-1065E-MAIL: [email protected] [email protected]: maidroc.fiu.edu
Conjugate heat transfer simulation was carried out using OpenFOAM platform. The University of Wisconsin solution was used as the cooling liquid. Laminar and turbulent UW flows were simulated by using Navier–Stokes equations and k-ε turbulent model.
Inlet temperature was 4oC. Outlet pressure was 101 kPa. Inlet velocities were 0.4 m/s and 1 m/s for internal circulations and 0.4 m/s for external circulation. All cooling container’s walls were assumed to be thermally insulated.
The average volumetric temperature was reduced to +5.0°C after 25 min. The maximum temperature was 12.0°C at 25 min.
Figure 5. Velocity and temperature distributions: a) and b) external circulation, c) and d) internal circulations.
Figure 6. Temperature distribution at: a) 0 min, b) 5 min, c) 10 min, d) 15 min, e) 25 min, and f) 60 min of cooling.
Thermo-Fluid Analysis
Cooling Container Design
Heart Geometry
• The U.S. Organ Procurement and Transplantation Network (OPTN)’s 2011 annual report indicated that approximately 18% of patients died due to lack of matching hearts [1].
• OPTN also reported that ONLY in a few states ~70% of adult wait-listed patients received a heart transplant within one year.
Figure 1. Percent of adult wait-listed patients in 2010 who received a deceased donor heart transplant within one year [1].
• OPTN prioritizes organ allocation to the most critically ill-heart matching candidates.
• To facilitate transplant coordination and to minimize ischemic time, five concentric geographic zones were defined by OPTN for the heart allocation.
• In most cases, the donor and the recipient of the compatible heart are at vastly different geographic locations thus preventing transplantation.
• An optimal preservation protocol is key to extending the current preservation time, thereby expanding the transplant geographical zones and increasing the number of heart transplants to the most critically ill-heart matching recipients.
References
1. Annual Report of the U.S. Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients: Transplant Data 2010-2011.
2. Zhang, Y., Bajaj, C. (2004). Finite element meshing for cardiac analysis. ICES Technical Report 04-26, the University of Texas at Austin.
3. Abdoli, A., Dulikravich, G. S., Bajaj, C., Stowe, D. F., and Jahania, M. S. (2014). Human Heart Conjugate Cooling Simulation: Unsteady Thermo-Fluid-Stress Analysis. International Journal of Numerical Methods in Biomedical Engineering, DOI: 10.1002/cnm.2662.
MAIDROCMultidisciplinary Analysis, Inverse Design, Robust Optimization and Control Laboratory
Simulation of Fully Conjugate Cooling Preservation Systems for Human Hearts Destined for Transplantation
Abas Abdoli1, George S. Dulikravich1, Chandrajit Bajaj2, David F. Stowe3 and M. Salik Jahania4
1Florida International University, 2University of Texas at Austin, 3Medical College of Wisconsin and 4Wayne State University
Heart Preservation and Research Objectives
• Cold (hypothermic) preservation is the most common preservation method. It is less complicated, less expensive compared to other methods.
• The idea behind this method is to decrease cell metabolism, thus decrease oxygen and glucose consumption, and carbon dioxide production.
Optimal cooling preservation should: • Cool the heart as fast and as uniformly as possible.• Prevent tissue damages due to thermal and hydraulic stress during
the cooling process. • Prevent damages due to ice crystals formation by avoiding
temperatures lower than the freezing temperature of water (+4oC).
Research Objectives • Design a cooling container including required inlets/outlets and
connections for coolant circulations.• Cool the heart as fast and as uniformly as possible.• Prevent tissue damages due to thermal and hydraulic stress during
the cooling process. • Prevent damages due to ice crystals formation by avoiding
temperatures lower than the freezing temperature of water (+4oC).
A cooling container with 214 mm length, 212 mm width and 282 mm height, 4 inlets and 4 outlets for internal circulation has been designed.
For circulating the coolant outside of the heart, two inlets (15 mm diameter) and two outlets (20 mm diameter) were placed in opposite corners of the container walls.
Figure 4. Cooling container with all connections and caps for internal circulations and inlets and outlets for external circulation.
• A cooling container for human heart preservation was designed. In this protocol external and internal cooling took place by pumping the UW solution inside and outside of the heart.
• Different cooling scenarios were simulated in which laminar flow, turbulent flow and unsteady periodic inlet velocities were applied.
• Results showed that the cooling case with laminar flow pattern, inside and outside of the heart had the best performance in terms of cooling the heart as fast as possible and at the same time preventing tissue damages due to thermal and shear stresses.
• Tave of the heart in this case was reduced to 5oC after 25 min.
Conclusion
Acknowledgement
The authors also gratefully acknowledge the FIU Instructional and Research Computing Center for providing HPC resources in conducting this project. The research of Chandrajit Bajaj was supportedin part by NIH grant R01-EB004873..
Innermost surfaces
Outermost surfaces
Inlet or Outlet for Internal Circulation
Inlet 1 for External Circulation
Outlet 1 and 2 for External Circulation
Inlet 2 for External Circulation
Stress Analysis
a) b) c)
d) e) f)
a) b)
c) d)