Micro-Scale Waste Heat Recovery from Stationary Internal Combustion Engines by Sub-Critical Organic Rankine Cycle utilizing Scroll Machinery

The movement towards renewable energy sources has created new challenges for energy production and has promoted the concept of distributed energy production. High efficiency Generators for Small Electrical and Thermal Systems (GENSETS) provide a viable solution to residential-scale power production at low cost. In an effort to improve the energy production efficiency of small scale internal combustion engine generators, a waste heat recovery (WHR) bottoming cycle can boost the operating efficiency of such systems by up to 7%. Organic Rankine Cycle (ORC) technology is a popular method of achieving WHR from low temperature heat sources. However, the application of ORC systems using the high-temperature exhaust stream of ICE generators as heat input is currently unexplored. Thermodynamic modeling of a sub-critical ORC system proved its viability as a bottoming cycle for ICE generators. The simulations also enabled the selection of the optimal working fluid for the specified application given the system restrictions. The refrigerant R245fa was selected for its high-temperature chemical stability and thermal efficiency. Detailed modeling that reflected the selected ORC components then provided insight into system performance with a range of ICE generators and further proved the system’s viability. The high temperature application required the creation of several prototype components to create an efficient ORC WHR system. By utilizing a novel evaporator heat exchanger, it is possible to establish a cycle with high superheat in an effort to minimize exergy destruction in the evaporation heat transfer process. Additionally, the sub-critical architecture of the ORC benefits from custom scroll-type expander and pump that match the designed pressure and volume ratios. However, the prototype ORC components required further development and testing and therefore, an experimental test stand was constructed to perform component evaluation and system performance measurement. Using the test stand, it was possible to evaluate two different types of scroll expander: the Oldham ring orbiting scroll, and the spinning scroll. A performance comparison is presented and the strengths and weaknesses of each are considered. Additionally, a performance comparison between the working fluid R245fa and its HFO replacement R1233zd(E) is presented in an effort to evaluate the feasibility of a working fluid change. The work performed on evaluating the different scroll machines presents a good first step in the successful development of an ORC bottoming cycle for ICE generators. Through further development, ORC WHR will become more feasible and assist in the goal of distributed energy production

Quality of Life and Cost-Effectiveness 1 Year After Total Hip Arthroplasty

Abstract: Quality of life index (Quality Of Well-Being [QWB]) was used to calculate the costs per quality of well year (QWY) in total hip arthroplasty (THA) and compare it to other interventions. Ninety-eight primary and/or revision THA were reviewed. Patients had minimum 1-year follow-up. Quality of life index was used to calculate the costs per QWY in primary and revision THA. Preoperative QWB for primary THA was 0.52 ± 0.06 SD; revision was 0.53 ± 0.07 SD. The QWB change at 1 year for primary THA was 0.08 ± 0.13 SD; revision THA was 0.06 ± 0.14 SD. Calculated costs per QWY were $5572 for primary procedures and$10 775 for revision procedures. Cost-effectiveness of THA compares favorably with other surgical and medical interventions such as epilepsy ablation surgery and gastric bypass surgery. Keywords: costeffectiveness, quality of life, primary hip arthroplasty, revision hip arthroplasty. © 2011 Elsevier Inc. All rights reserved. Health care expenditures will hit the 2. Surgeons performing total hip arthroplasty, especially primary hip surgery, have had the deepest cuts. The reimbursement for a primary arthroplasty today is 39% less than what it was in 1991. The current reimbursement for revision hip arthroplasty is only 5% more than the reimbursement for primary hip arthroplasty Cost-utility ratios allow an investigator to calculate the relative cost-effectiveness of health care interventions In previous work, our group has reported on the quality of life immediately after knee arthroplasty and the dollar value of a QWY obtained by a total knee arthroplasty Methods Patient Selection Two hundred seventy-six (276) consecutive hip procedures were performed. Sixty-five hemiarthroplasty procedures were excluded; 32 patients (64 procedures

Low-Cycle Fatigue of Ultra-Fine-Grained Cryomilled 5083 Aluminum Alloy

The cyclic deformation behavior of cryomilled (CM) AA5083 alloys was compared to that of conventional AA5083-H131. The materials studied were a 100 pct CM alloy with a Gaussian grain size average of 315 nm and an alloy created by mixing 85 pct CM powder with 15 pct unmilled powder before consolidation to fabricate a plate with a bimodal grain size distribution with peak averages at 240 nm and 1.8 lm. Although the ultra-fine-grain (UFG) alloys exhibited considerably higher tensile strengths than those of the conventional material, the results from plastic-strain-controlled low-cycle fatigue tests demonstrate that all three materials exhibit identical fatigue lives across a range of plastic strain amplitudes. The CM materials exhibited softening during the first cycle, similar to other alloys produced by conventional powder metallurgy, followed by continual hardening to saturation before failure. The results reported in this study show that fatigue deformation in the CM material is accompanied by slight grain growth, pinning of dislocations at the grain boundaries, and grain rotation to produce macroscopic slip bands that localize strain, creating a single dominant fatigue crack. In contrast, the conventional alloy exhibits a cell structure and more diffuse fatigue damage accumulation

Low-Cycle Fatigue of Ultra-Fine-Grained Cryomilled 5083 Aluminum Alloy

The cyclic deformation behavior of cryomilled (CM) AA5083 alloys was compared to that of conventional AA5083-H131. The materials studied were a 100 pct CM alloy with a Gaussian grain size average of 315 nm and an alloy created by mixing 85 pct CM powder with 15 pct unmilled powder before consolidation to fabricate a plate with a bimodal grain size distribution with peak averages at 240 nm and 1.8 μm. Although the ultra-fine-grain (UFG) alloys exhibited considerably higher tensile strengths than those of the conventional material, the results from plastic-strain-controlled low-cycle fatigue tests demonstrate that all three materials exhibit identical fatigue lives across a range of plastic strain amplitudes. The CM materials exhibited softening during the first cycle, similar to other alloys produced by conventional powder metallurgy, followed by continual hardening to saturation before failure. The results reported in this study show that fatigue deformation in the CM material is accompanied by slight grain growth, pinning of dislocations at the grain boundaries, and grain rotation to produce macroscopic slip bands that localize strain, creating a single dominant fatigue crack. In contrast, the conventional alloy exhibits a cell structure and more diffuse fatigue damage accumulation

Taguchi Loss Function for Varus/Valgus Alignment in Total Knee Arthroplasty

Methods of designing equipment to improve quality have been developed by Taguchi. A key feature of these methods is the development of loss function, which quantifies the financial cost (loss) resulting from deviations from target dimensions. Total knee arthroplasties can fail due to prosthetic component malalignment. A Taguchi loss function for varus/valgus alignment of the prosthesis and revision rates was developed. Six studies were identified from a comprehensive literature search. Varus and extreme valgus alignments correlated with an increased percentage of prosthetic failure. A loss function of L( y) = $326.80y2 , where y was deviation from ideal varus/valgus angle, was determined. The expected loss function was EL=$326.80y¯2+s2 , where y¯ was the mean deviance from the ideal varus/valgus angle and s2 was the variance in varus/valgus angle. This loss function was used to estimate the cost savings of using computer-assisted surgical navigation in total knee arthroplasty (TKA). The average savings of a navigated TKA versus a conventional TKA, based on the expected loss equation derived from the Taguchi loss function, was $2,304 per knee. The expected loss function derived here can serve as a tool for biomedical engineers seeking to use Taguchi quality engineering methods in designing orthopaedic devices

Loss of life years after a hip fracture: Effects of age and sex

Background Patients with a hip fracture have a high mortality; however, it is not clear how large the loss of life-years is over an extended observation period