Experimental study of a counter-flow regenerative evaporative cooler

This paper aims to investigate the operational performance and impact factors of a counter-flow regenerative evaporative cooler (REC). This was undertaken through a dedicated experimental process. Temperature, humidity and flow rate of the air flows at the inlet, outlet and exhaust opening of the cooler were tested under various operational conditions, i.e., different inlet air conditions, feed water temperature and evaporation rate were also correspondingly measured. It was found that the wet-bulb effectiveness of the presented cooler ranged from 0.55 to 1.06 with Energy Efficiency Ratio (EER) rated from 2.8 to 15.5. The major experimental results were summarised below: 1) the wet-bulb effectiveness was significantly enhanced through either ways of increasing inlet wet-bulb depression or reducing intake air velocity, or alternatively by increasing working-to-intake air ratio; 2) the cooling capacity and EER of cooler was rapidly increased by means of increasing inlet wet-bulb depression or increasing intake air velocity, or reducing working-to-intake air ratio instead; 3) the effectiveness reduced by less 5% while feed water temperature increased from 18.9 to 23.1°C; 4) apparent acceleration in water evaporation rate was gained from increasing inlet wet-bulb depression or air velocity. The presented cooler showed 31% increase in wet-bulb effectiveness and 40% growth in EER compared to conventional indirect evaporative cooler. The research helped identifying the performance of a new REC with enhanced performance and thus contributed to development of energy efficient air conditioning technologies, which eventually lead to significant energy saving and carbon emissions reduction in air conditioning sector

Energy saving potential of a counter-flow regenerative evaporative cooler for various climates of China: Experiment-based evaluation

© 2017 Recently there has been growing interest in regenerative evaporative coolers (REC), which can reduce the temperature of the supply air to below the wet-bulb of intake air and approach its dew-point. In this paper, we designed, fabricated and experimentally tested a counter-flow REC in laboratory. The REC's core heat and mass exchanger was fabricated using stacked sheets composed of high wicking evaporation (wickability of available materials was measured) and waterproof aluminium materials. The developed REC system has a much higher cooling performance compared to conventional indirect evaporative cooler. However, the decision to use the REC for China buildings depends on a dedicated evaluation of the net energy saved against the capital expended. Such an evaluation requires the hourly-based data on the availability of cooling capacity provided by the REC for various climates. The paper used an experiment-based method to estimate the cooling capacity and energy savings provided by the proposed REC for China's various climates. By using the experimental results and regional hourly-based weather data, the energy saving potential of the REC against an equivalent-sized mechanical air conditioner alone was analysed. The results indicate that, for all selected regions, the REC could reduce 53–100% of cooling load and 13–58% of electrical energy consumption annually

OR-018 The study of acupuncture intervention on the dynamic changes of Ca2+, Na+, H2O2 flux at earlier time points of rat skeletal muscle regeneration following eccentric exercise

Objective  In this study, the Non-invasive Micro-test Technique was adopted to study the dynamic changes of Ca2+, Na+ , H2O2 flux during the early phase of skeletal muscle regeneration (0–24 h post-injury) after acupuncture intervention, and to explore the role of interaction between TRP channel and NADPH oxidase 2(NOX2) in the acupuncture mechanism. Methods  324 healthy male Wistar rats were randomly divided into 6 groups: blank control group (C), electrical stimulation group (E), electrical stimulation group with acupuncture intervention (EA), electrical stimulation gropu with acupuncture +TRP channel inhibitor (EAT ), electrical stimulation gropu with acupuncture + NOX2 inhibitor (EAN), electrical stimulation gropu with acupuncture + placebo (EAP). Except for group C, the animal model of eccentric induced skeletal muscle injury  was established by electrostimulation on gastrocnemius of anaesthetised rats in vivo.Immediately after electrical stimulation, GdCl3, apocynin and PBS buffer were injected by tail vein in EAT, EAN and EAP respectively. After 30 min, gastrocnemius muscle belly were stuck with acupuncture needles (diameter of 0.13 mm) in EA, EAT, EAN and EAP respectively. Shortly afterwards, a special polypropylene ring-shaped perforated vessel wall was sutured to the exposed gastrocnemius muscle, and to measure Ca2+, Na+, H2O2 fluxes by non-invasive micro-test technique in the phase of retaining needle, needle drawing immediately, 3h, 6h and 24h, respectively. The phase and time of detection in the C and E groups were consistented. Results  1 When the gastrocnemius muscle was in a resting state, Ca2+ and Na+ were influx in small amounts, and H2O2 had a small eflux. 2 Effect of eccentric Exercise and acupuncture on the dynamic changes of Ca2+ flux at different phases : ① In the E, a small eflux occurred at 0min, 10min and 3h, and the eflux suddenly increased significantly at 6 h (p<0.05), followed by a small eflux at 24h; ② In the EA, a small eflux occurred during retaining needle and needle drawing immediately, and Surprisingly, a small influx was observed at 3h. After that, the eflux increased suddenly at 6h and 24h, and the eflux peaked at 24h, which was significantly different from the E group at 24h. (p<0.05); ③ The EAT showed a significant influx trend. Specifically, except a small eflux in the retention period and 3h phase, significant influx occurred immediately after the needle pulling、6h and 24h. Compared with C and EA, there was no statistically significant difference in net flux (influx and efflux), but Ca2+ oscillation amplitude (influx and eflux fluctuation amplitude) in EAT was significantly increased (p<0.001, p<0.01, respectively); ④ In EAN, the eflux was dominant. Specifically, there was significant influx in the retention period and immediately after needle pulling, and suddenly significant eflux was observed at 3h and 6h. The 6h phase was significant difference than that of E (p<0.05), afterwards, the eflux was significantly decreased at 24h, and was significantly different from 6h (p<0.05); ⑤ The EAP flowed outward at all phases, and the overall trend was similar to the E group. The eflux peaked at needle drawing immediately, which was significantly different from that of the concurrent phase E and EA (p<0.05), and the eflux was significantly decreased at 24h. 3 Effect of eccentric exercise and acupuncture on the dynamic changes of Na+ flux at different phases : ① In the E, the eflux occurred at during retaining needle and needle drawing immediately, and the influx occurred suddenly at 3h and 6h. There was a significant difference between 6h and the C (p<0.001), and the eflux again occurred at 24h;② In the EA, the flux occurred during retaining needle and needle drawing immediately, and after that, efflux occurred at the 3h, 6h, and 24h;③ The EAT efflux at all phases was in line with the trend of changes in the E. ④ The EAN only eflux at 6h (p<0.05), while the rest of the phases flowed inward, and the influx peaked at 3h, which was significantly different from that at needle drawing immediately (p<0.05). The influx amplitude decreased at 24h, showing a significant difference from 3h (p<0.01). ⑤ The EAP only flowed inward at 3h, and the rest of the phases flowed outward. 4 Effect of eccentric exercise and acupuncture on the dynamic changes of H2O2 flux at different phases : ① In the E, the influx occurred only at 10 min, and the rest of the phases flowed outward with an increasing trend. The peak value were reached at 24h, showing a significant difference with C group and 0 min(p<0.01), and extremely significant with 3h (p<0.001) and 6h (p<0.05);② EA only flowed inward during retaining needle, all other phases flowed outward and peaked at 24h, but the eflux was less than that of E and there was a significant difference at 6h with E (p<0.05);③ The EAT group flowed outward at all phases and reached the peak at 3h, showing a significant difference compared with the E and EA at the same phases (p<0.001); ④The EAN flowed outward at each time phase and peaking needle drawing immediately, but the flow velocity was higher than that of the EAT. There was an extremely significant difference compared with EA at the peaking phase (P<0.001) and a significant difference with EAT at the same phase (p<0.05);⑤ In the EAP, all phases flowed outward, but the flow rate was less than the EAT and EAN. Conclusions  1  In the early subsequent phase of skeletal muscle regeneration, Ca2+ efflux  decreased, while Na+ influx increased, accompanied by increased H2O2 efflux. 2  Acupuncture intervention increased Ca2+ efflux in the early subsequent phase of skeletal muscle regeneration and advanced the Na+ influx phase, with the decrease of H2O2 efflux, and the effect was related to the interaction of TRP channels synergize with NOX2 Activity

Comparative study on the sealing performance of packer rubber based on elastic and hyperelastic analyses using various constitutive models

Evaluation of the sealing performance of the packer rubber varies according to specific simulation models. This paper aims at revealing the difference between elastic and hyperelastic analyses using the finite element mothed (FEM). The study extracts the hyperelastic parameters of the neo-Hookean, the Mooney-Rivlin, and the Yeoh models from a uniaxial tensile test. Then, the setting process of a mechanical packer is simulated by elastic and hyperelastic calculations. We compare the deformed configuration and the contact stress given by these models. Our results show that the Yeoh model produces the minimum residual sum of squares (RSS) among the hyperelastic models for hydrogenated nitrile butadiene rubber (HNBR). The mooney-Rivlin model has a negative parameter, making the calculation unstable. The linear elastic model fails to simulate the setting process, while the neo-Hookean model overestimates the contact stress. Despite the similar stress distribution, the nonlinear elastic model provides a 17.8% higher contact stress on average than the Yeoh model. A parametric study based on the Yeoh model points out that the sub-thickness of the packer rubber needs an elaborate design. Reducing the sub-thickness could increase the contact stress but decrease the seal length in the force control mode. From an engineering perspective, this study demonstrates that it needs to pay more attention when selecting an appropriate material model and a sound analysis method to evaluate the sealing performance of an oil packer

Evaluation of Mixed-Mode Ventilation Thermal Performance and Energy Saving Potential from Retrofitting a Beijing Office Building

Mixed-mode cooling can effectively reduce the energy consumption of building cooling while satisfying the thermal comfort of occupancy and indoor air quality requirements. This paper predicted the thermal performance and energy-saving potential of an existing Beijing office building (in continental climates) operated in a mixed-mode from April to October. For the natural ventilation mode, the results predicted by simulation were validated with the results of experiments conducted in October 2021 and April 2022. Occupancy thermal comfort of the mixed-mode building was predicted using Predicted Mean Vote (PMV) and adaptive comfort models. The predictions demonstrated acceptable satisfactory thermal comfort for the occupancy. The results showed that the mixed-mode building’s annual cooling energy use is reduced by around 45% compared to the air-conditioned building. In addition, the building’s indoor temperature and velocity distributions were predicted using a Computational Fluid Dynamics (CFD) simulation. The validation showed a satisfactory agreement between CFD simulation and measurement data. It is found from CFD results that cross-ventilation can provide thermal comfort for the occupancy while improving fresh air requirements. The suggested that operational strategies of mixed-mode cooling can be used in office buildings in continental climates. Retrofitting the existing office building can bring a significant amount of energy saving

High intrinsic dissipation of graphyne nanotubes

We utilize molecular-dynamics simulations to report the first investigation of energy dissipation of two different doubly clamped graphyne nanotubes (GNTs), where the point of emphasis is to compare their dissipation characteristics with those of carbon nanotube (CNT). The obtained results demonstrate that: (a) GNTs exhibit significantly higher energy dissipation, and thus lower quality (Q) factor which is generally five times lower than that of CNT; (b) the Q factor of GNT further reduces with the increasing percentage of acetylenic linkages, which originates from the larger vibrational mismatch between the acetylenic linkage (sp C-C bonds) and the hexagonal ring (sp2 C-C bonds); (c) the application of tensile strain is found to be highly beneficial to improving the Q factor of GNTs, especially for those with higher percentage of acetylenic linkages. These findings enable a first insight into the damping behavior of GNTs and also offer a significant guideline for the future design of GNT-based devices

Study on the Preferred Application-Oriented Index for Mental Fatigue Detection

Most of the research on mental fatigue evaluation has mainly concentrated on some indexes that require sophisticated and large instruments that make the detection of mental fatigue cumbersome, time-consuming, and difficult to apply on a large scale. A quick and sensitive mental fatigue detection index is necessary so that mentally fatigued workers can be alerted in time and take corresponding countermeasures. However, to date, no studies have compared the sensitivity of common objective evaluation indexes. To solve these problems, this study recruited 56 human subjects. These subjects were evaluated using six fatigue indexes: the Stanford sleepiness scale, digital span, digital decoding, short-term memory, critical flicker fusion frequency (CFF), and speed perception deviation. The results of the fatigue tests before and after mental fatigue were compared, and a one-way analysis of variance (ANOVA) was performed on the speed perception deviation. The results indicated the significance of this index. Considering individual differences, the relative fatigue index (RFI) was proposed to compare the sensitivity of the indexes. The results showed that when the self-rated fatigue grade changed from non-fatigue to mild fatigue, the ranges of RFI values for digital span, digital decoding, short-term memory, and CFF were 0.175–0.258, 0.194–0.316, 0.068–0.139, and 0.055–0.075, respectively. Correspondingly, when the self-rated fatigue grade changed to severe fatigue, the ranges of RFI values for the above indexes were 0.415–0.577, 0.482–0.669, 0.329–0.396, and 0.114–0.218, respectively. These results suggest that the sensitivity of the digital decoding, digital span, short-term memory, and CFF decreased sequentially when the self-evaluated fatigue grade changed from no fatigue to mild or severe fatigue. The RFI individuality of the speed perception deviation is highly variable and is not suitable as an evaluation index. In mental fatigue testing, digital decoding testing can provide faster, more convenient, and more accurate results