Manufacturing Process Design for a Stamped Microchannel High-Temperature Recuperator

Microchannel high temperature recuperators have the advantage of higher heat transfer coefficients and lower size and weight than traditional high temperature recuperators. However, the industrial application of microchannel recuperators are restricted by the high cost of photochemical machining and diffusion bonding. The objective of this paper is to introduce a manufacturing process design of a microchannel high-temperature recuperator produced by stamping and laser welding. The potential cost of the 3.5 kWt recuperator is estimated based on a conceptual design of the manufacturing process. Subsequently, experiments are conducted to validate that cost model by demonstrating process capability. A stamping vendor was contracted to produce stamped Inconel 625 laminae. The laminae were laser welded together into a sub-scale high temperature recuperator that was evaluated in terms of effectiveness and pressure drop. The recuperator was tested at an operating pressure of 207 kPa (30psi) and an operating temperature of 200°C and found to be within 2.7% of its expected effectiveness at a mass flow rate of 0.99 g/s. However, pressure drops were found to be 2.5 to 4.5 times what was expected at this flow rate. Therefore, additional work is needed to reduce malformations within the structure produced during fabrication. Pressure drops could be lowered by designing a fixture to control clamping pressures during the gas tungsten arc welding of the housing. Further, internal support features are needed within cold flow channels to help prevent channel collapse brought on by springback in stamping and residual stresses in laser welding

Conceptual Design of a Manufacturing Process for an Automotive Microchannel Heat Exchanger

Calls for higher fuel efficiency in the United States and Europe are driving the need for waste heat recovery in automotive markets. While conventional heat exchangers can be designed to meet the heat duty requirement, the resulting volume, weight, and thermal mass are too large for rapid transient response and packaging of the device. The lightweight, compact form factor of microchannel heat exchangers with submillimeter flow passages is attractive for automotive applications. However, the industrial use of microchannel heat exchangers continues to be inhibited by high manufacturing costs. The objective of this paper is to develop a microchannel heat exchanger concept capable of meeting the cost and performance goals for an automotive application. So-called printed-circuit microchannel heat exchangers are produced using a stacked-lamina approach in which individual metal laminae are photochemically machined and diffusion bonded. Here, the conceptual design of a microchannel heat exchanger produced using more conventional stamping and joining technologies is discussed for an automotive application. The device is sized to provide waste heat recovery from an exhaust stream to engine coolant for a representative passenger vehicle with acceptable pressure loss. Using the specified design, a process-based cost model is presented showing cost modeling efforts to date including the capital investment and cost-of-goods-sold as a function of annual production volume. The initial results show a pathway for the cost effective integration of compact microchannel heat exchangers into advanced vehicle thermal management systems

Long-term Effectiveness and Adoption of a Cellphone Augmented Reality System on Patients with Stroke: Randomized Controlled Trial

BackgroundA serious game–based cellphone augmented reality system (CARS) was developed for rehabilitation of stroke survivors, which is portable, convenient, and suitable for self-training. ObjectiveThis study aims to examine the effectiveness of CARS in improving upper limb motor function and cognitive function of stroke survivors via conducting a long-term randomized controlled trial and analyze the patient’s acceptance of the proposed system. MethodsA double-blind randomized controlled trial was performed with 30 poststroke, subacute phase patients. All patients in both the experimental group (n=15) and the control group (n=15) performed a 1-hour session of therapy each day, 5 days per week for 2 weeks. Patients in the experimental group received 30 minutes of rehabilitation training with CARS and 30 minutes of conventional occupational therapy (OT) each session, while patients in the control group received conventional OT for the full 1 hour each session. The Fugl-Meyer Assessment of Upper Extremity (FMA-UE) subscale, Action Research Arm Test (ARAT), manual muscle test and Brunnstrom stage were used to assess motor function; the Mini-Mental State Examination, Add VS Sub, and Stroop Game were used to assess cognitive function; and the Barthel index was used to assess activities of daily living before and after the 2-week treatment period. In addition, the User Satisfaction Evaluation Questionnaire was used to reflect the patients’ adoption of the system in the experimental group after the final intervention. ResultsAll the assessment scores of the experimental group and control group were significantly improved after intervention. After the intervention. The experimental group’s FMA-UE and ARAT scores increased by 11.47 and 5.86, respectively, and were both significantly higher than the increase of the control group. Similarly, the score of the Add VS Sub and Stroop Game in the experimental group increased by 7.53 and 6.83, respectively, after the intervention, which also represented a higher increase than that in the control group. The evaluation of the adoption of this system had 3 sub-dimensions. In terms of accessibility, the patients reported a mean score of 4.27 (SD 0.704) for the enjoyment of their experience with the system, a mean 4.33 (SD 0.816) for success in using the system, and a mean 4.67 (SD 0.617) for the ability to control the system. In terms of comfort, the patients reported a mean 4.40 (SD 0.737) for the clarity of information provided by the system and a mean 4.40 (SD 0.632) for comfort. In terms of acceptability, the patients reported a mean 4.27 (SD 0.884) for usefulness in their rehabilitation and a mean 4.67 (0.617) in agreeing that CARS is a suitable tool for home-based rehabilitation. ConclusionsThe rehabilitation based on combined CARS and conventional OT was more effective in improving both upper limb motor function and cognitive function than was conventional OT. Due to the low cost and ease of use, CARS is also potentially suitable for home-based rehabilitation. Trial RegistrationChinese Clinical Trial Registry ChiCTR1800017568; https://tinyurl.com/xbkkyfy