SBIR-STTR Award

Technology Assessment and Transfer, Inc. in collaboration with the University of Cincinnati and industrial partner Carrier proposes the development and demonstration of light weight, compact additive manufactured (AM) alumina ceramic heat exchangers with exceptional heat transfer properties for a broad spectrum of residential and industrial air to refrigerant HVAC applications. The higher thermal conductivity, dimensional stability, low thermal expansion, corrosion resistance and light weight of alumina makes it the preferred choice over high temperature metals. The proposed approach includes the following tasks: 1)Develop models of compact heat exchanger designs that capitalize on digital light projection (DLP) AM capabilities and predict thermal performance improvements over traditional sheet metal designs, 2) Fabricate sub-scale DLP heat exchanger designs, 3) Measure performance (pressure drop and heat transfer) in in a low-speed air-flow wind tunnel, 4) Compare performance to modeling predictions, 5) Identify dimensional shortfalls relative to design requirements and 6) Prepare a Final Report with all the results, analyses, conclusions and recommendations for accelerated, scale up Phase 2 effort. In Phase 2 UC will incorporate the most up-to-date fabrication capabilities into the designs (e.g. minimum feature size limit, minimum channel size, microstructure, properties) for scale up and testing by Carrier. Commercial applications of these highly efficient, microchannel ceramic heat exchangers will produce substantial energy savings in residential and commercial heat pumps and air conditioners. In addition, spin off opportunities include industrial, automobile, truck. aircraft engine and geothermal heat recovery. Other applications include electronic power modules, radar, laser and other systems with substantial cooling needs.

DoE is seeking “next-generation non-metallic heat exchanger systems to improve the energy efficiency of heat pumps and air conditioners over a broad range of operating conditions for building and industrial applications that leverage Conductivity-enhanced materials for Affordable, Breakthrough Leapfrog Electric and Thermal Applications (CABLE) non-metallic materials with enhanced thermal conductivity.” Specially, this subtopic “seeks new designs for higher conductivity heat exchangers suitable for condensers or evaporators in air conditioners or heating-only heat pumps, as well as heat exchangers suitable for both condensing and evaporating for reversible heat pumps.” The overall approach of the Phase 1/Phase 2 SBIR efforts between Technology Assessment and Transfer, Inc., the University of Cincinnati (UC) and industrial partner Carrier was to demonstrate the feasibility of Digital Light Projection (DLP) additive manufactured (AM) alumina ceramic microchannel heat exchangers with exceptional heat transfer capability via a combination of predictive modeling, experimental HXer AM, heat transfer and pressure performance measurements and subsequent refinements for industrial air to refrigerant HVAC applications. The higher thermal conductivity, dimensional stability, low thermal expansion, corrosion resistance and light weight of alumina makes it the preferred choice over high temperature metals. The Phase I program successfully achieved all its following objectives: Objective 1. Establish predictive models of compact heat exchangers with exceptional performance Objective 2. Establish DLP AM protocols for a plain fin alumina heat exchanger design Objective 3. Evaluate performance of plain fin alumina heat exchanger and compare with Modeling predictions Objective 4. Demonstrate DLP high-quality enhanced heat exchanger designs with exception heat transfer performance unachievable by conventional fabrication methods. At the end of Phase 1, DLP trapezoidal shaped slotted fin converging-diverging heat exchangers exhibited exceptional heat transfer performance, matched modeling predictions and maintained a low pressure drop, conclusively demonstrating the major advantage of AMThe Phase 2 effort will use a similar approach to optimize alumina heat exchangers with exceptional heat transfer properties for a Carrier Corporation design. The specific steps include the following: (a) evaluation of the thermal-hydraulic performance of selected surfaces using predictive correlations, and/or scoping computational simulation of targeted fin cores, (b) refinement of DLP resin formulations, build parameters, binder burn out and sintering protocols required to build larger size and more complex microchannel heat exchangers, (c) experimental testing to evaluate the liquid-to-air enhanced heat transfer, with extended parametric computational performance simulation to make recommendations for prototype development, as outlined by the Industrial partner, Carrier, for single-phase forced convection heating and/orcooling HVAC applications, (d) carrying out needed optimization of the prototype heat exchanger to achieve high performance objectives and (e) preparing a Final Report with all the results, analyses, conclusions and recommendations for scaled up transition effort.Commercial Applications and Other Benefits Commercial applications of these highly efficient, microchannel ceramic heat exchangers will produce substantial energy savings in residential and commercial heat pumps and air conditioners. In addition, spin off opportunities include industrial, automobile, truck. Micro turbine engines and geothermal heat recovery. Other applications include electronic power modules, radar, laser and other systems with substantial cooling needs.