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This paper proposes and simulates a desiccant air cooling system integrated with a vapor compression cooling unit and a heat recovery unit for an office building in Çanakkale, Turkey, during the summer season. The required electrical energy for equipment of the proposed system is supplied by an Solid Oxide Fuel Cells (SOFC) unit using human waste as fuel. Moreover, some of the waste heat generated by the SOFC is used to regenerate the desiccant wheel. The simulation also includes the effects of three different refrigerants for the vapor compression cooling unit. Among the refrigerants, the highest electrical COP was obtained for the system using R1234ze(Z), which is 3.14% and 2.40% higher than the systems using R717 and R1233zd(E), respectively. Additionally, the system using R1234ze(Z) achieved electrical savings of 9.97% and 9.23% compared to the other systems. These electrical savings resulted in fuel savings of 1.19% and 0.90% for R1234ze(Z) compared to R717 and R1233zd(E), respectively. During the summer season, the electricity production from the existing SOFC unit met 82.00% of the total electricity consumption of the desiccant hybrid cooling system. Furthermore, a difference of 3984.56 kWh in primary energy consumption was identified between the desiccant hybrid cooling systems operating with the SOFC and without the SOFC during the summer season.

In this work, melting of a high-temperature inorganic phase change material (PCM) eutectic (with a melting point of 569 °C) within a vertical cylindrical tank has been experimentally investigated. To promote the heat transfer rate, a periodic structure that is constructed by a commercial SS-304 mesh screen has been considered and immersed into the PCM tank. Thermal characteristics of the PCM-periodic structure tank under different initial temperatures (450, 490 and 546 °C) and wall temperatures (620, 640, 660, 680 and 700 °C), are then investigated and reported. The presented experimental data can facilitate practical engineers to find the best operating condition of similar PCM tanks; meanwhile, it can also be employed for the investigation of thermal response of transient heat conduction before melting starts.

The transportation of perishable products is a crucial activity that must be carefully managed along the cold chain. The refrigerated transport aims at ensuring the suitable transportation conditions by maintaining the desired temperature level in the refrigerated compartment. Moreover, the carriage of perishable fresh foodstuffs calls for additional precautions due to the intrinsic metabolic activity of fresh foods which causes them to be highly temperature sensitive. About 30% of fresh products perishes on the route due to the loss of suitable temperature values. Recently, scientists have been focusing their efforts on the development of innovative solutions, which ensure a proper refrigerated products distribution and transportation in a more environmental-friendly and cost-effective way. Hence, in this work, a novel concept of a Latent Thermal Energy Storage (LTES) system consisting of an insulation layer of poly-urethane foam wrapping a second one of Phase Change Material (PCM) is proposed. In particular, the thermal performance is investigated by running numerical CFD analyses in Ansys Fluent. The effect of different product loads (25%-50%-75%) is studied. Besides, the contributions of the heat respiration and diverse food pre-cooling temperatures on the system performance are also analysed. For the long-distance route no door openings nor additional heat infiltrations are considered.

Foodstuff has to be transported from where it is produced or packaged to the market. It is important to control the temperature and humidity of the delivered food to minimize the waste and ensure customer satisfaction. At the same time, unfortunately, the transport sector is among the polluting sectors. Therefore, innovative solutions have been proposed such as the adoption of Latent Thermal Energy Storage (LTES) systems based on Phase Change Materials (PCMs) to control the food temperature. Such systems minimize the fuel consumption and thereby reduce the emission. LTES systems rely on the phase change process to absorb and store heat in a more sustainable way while ensuring a nearly constant temperature for the foodstuff while being transported.Hence, we first present a general overview of the application of PCMs at low temperatures. Then, the literature on the adoption of PCMs in the refrigerated transport sector is critically surveyed. Different proposals offered in the literature are recovered, compared, and critically assessed based on their merits. Despite the differences between the proposed technologies, significant advantages in terms of temperature uniformity in the refrigerated space, product thermal stress reduction, product quality, energy consumption, and pollutant emissions reduction are reported in the literature as surveyed in this paper.

This paper rigorously validates the RANS models against the DNS on predicting turbulent flow and heat transfer of highly buoyant horizontal supercritical fluids. The low-Reynolds number turbulence models of RNG, AKN, V2F and (k−ω) SST that are recommended in literature are selected. Also, the LS model demonstrating good performance in some in-house CFD codes has been reimplemented via User-Defined Functions (UDFs) and examined for supercritical simulations, in particular with strong buoyancy effects. The results indicated that the AKN model works best among the tested models on the reproductions of some bulk parameters that are of interest (such as wall temperature, Nusselt number and skin friction coefficient) and the distortions of the turbulent velocity profile caused by the strong buoyancy, closely followed by the V2F model. The UDFs implemented LS model exhibits much better performances than the originally incorporated version in FLUENT, which is attributed to the more proper model implementation that leads to better treatments on the fluid flow and heat transfer, especially in the near-wall regions. Regarding the reproductions on the turbulence kinetic energy generations under the studied conditions, the RANS models are unable to give satisfactory results, the simulated suppression in the top half is more drastic. Similar to the vertical supercritical fluids, with quite high-strength buoyancy, the heat transfer recovers around the horizontal pipe top wall but the RANS models' response to the “recovery” is poor. The model performance on reproducing the turbulent statistics is closely related to the implementation of the vital structural parameters.

Solar enhanced natural draft dry cooling tower (SENDDCT) is a novel heat rejection device for thermal power plant, which uses solar energy to reheat the air after the heat exchanger and therefore improves the ventilation of the tower for performance enhancement. This paper develops 3-D models to compare the effects of circular/sawtooth arrangements of heat exchanger on cooling performance of a 140 m high SENDDCT. The result shows that sawtooth arrangement can improve the ventilation and heat dissipation rate of SENDDCTs. Under no crosswind condition, the flow field distributions of sawtooth and circular arrangements are similar in the tower. The ventilation and heat dissipation rate of sawtooth arrangement increases by 34.0 % and 46.8 % respectively when compared with circular arrangement under no crosswind condition. Under crosswind condition, the flow field of sawtooth arrangement is less affected by crosswind than that of circular arrangement. The ventilation rate and heat dissipation rate of sawtooth arrangement increases by 38.5 % and 65.0 % respectively when compared with circular arrangement at crosswind speed of 3 m/s. This study verifies that the sawtooth arrangement can weaken the crosswind effect and improve the cooling performance of SENDDCT and provides guidance for the optimal arrangement of heat exchanger for the SENDDCT.

Power plants based on organic Rankine cycle (ORC) are known for their capacity in converting low and medium-temperature energy sources to electricity. To find the optimal operating conditions, a designer must evaluate the ORC from different perspectives including thermodynamic performance, technological limits, economic viability, and environmental impact. A popular approach to include different criteria simultaneously is to formulate a bi-objective optimization problem. This type of multi-objective optimization (MOO) allows for finding a set of optimal design points by defining two different objectives. Once the optimization is completed, the decision-making analysis shall be carried out to identify the final design solution. This study aims to develop a decision-making tool for facilitating the choice of the optimal design point. The proposed procedure is coded in MATLAB based on the commonly used Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). By providing the capability to graphically identify the decisions taken, the tool developed in the study is called Tracking and Recognizing Alternative Design Solutions (TRADeS). Analysis of our data shows that certain regions of Pareto set points should be excluded from the design space. It was noted that in these regions a high rate at which one of the objectives moves away from its ideal value coincides with a low rate at which the second criterion approaches its ideal solution. Hence, it was recommended that the criteria weights corresponding to excluded regions of the Pareto set should be discarded when selecting the final design point. By comparing the results obtained using the proposed model to those of existing decision-making techniques, it was concluded that while the known approaches are appropriate for an easy and fast selection of the final design point, the presented procedure allows for a more comprehensive and well-rounded design. It was shown that our design tool can be successfully applied in the decision-making analysis for problems that aim at optimizing the ORC using two design criteria. Finally, the proposed software benefits from a generic structure and is easy to implement which will facilitate its use in other industrial applications.

Gasification of coal or biomass with in-situ CO2 capture is an emerging technology aiming to address the problem of climate change. Development of a CO2 sorbent with desirable properties and understanding the behavior of such a material in carbonation/calcination reactions is an important part of developing the technology. In this paper, we report experimental results describing the carbonation behavior of three synthetic CaO-based sorbents. We also present a physically-based model of the reactive transport processes in sorbent particles, which have complicated pore structures. This modeling is based on the conditional approach (i.e., conditional moment closure (CMC)), which has proven to be successful in modeling reactive transport phenomena in porous media. The model predictions are in good agreement with the experimental data.

Abstract: This paper investigates entropy generation due to forced convection in a porous medium sandwiched between two parallel plates one of them being subjected to a uniform heat flux and the other one insulated. Our results showed that viscous dissipation will affect the entropy generation rate at the centerline of the channel since viscous dissipation is a quadratic function of velocity [1-3]. Neglecting the Darcy dissipation term in comparison with the terms added by Al-Hadrami et al. [4], will lead to the misunderstanding that fluid friction has no effect on the entropy generation rate at the tube centerline where the velocity derivative vanishes due to symmetry. Though the term added by [4] is O(Da) compared to the Darcy term one should not drop it unless the clear flow solution is sought [5-7]. Moreover, as stated by Nield [1], one should not use just the term involving velocity derivatives, as some authors have done in the past, for example [8-11]. Though in this paper the viscous dissipation effects in the energy equation are neglected, we have take them into account when it came to the entropy generation analysis.

This paper focuses on the optimization of a Solar-Enhanced Natural-Draft Dry-Cooling Tower (SENDDCT), originally designed by the Queensland Geothermal Energy Centre of Excellence (QGECE), as the air-cooled condenser of a geothermal power plant. The conventional method of heat transfer augmentation through fin-assisted area extension is compared with a metal foam-wrapped tube bundle. Both lead to heat-transfer enhancement, albeit at the expense of a higher pressure drop when compared to the bare tube bundle as our reference case. An optimal design is obtained through the use of a simplified analytical model and existing correlations by maximizing the heat transfer rate with a minimum pressure drop goal as the constraint. Sensitivity analysis was conducted to investigate the effect of sunroof diameter, as well as tube bundle layouts and tube spacing, on the overall performance of the system. Aiming to minimize the flow and thermal resistances for a SENDDCT, an optimum design is presented for an existing tower to be equipped with solar panels to afterheat the air leaving the heat exchanger bundles, which are arranged vertically around the tower skirt. Finally, correlations are proposed to predict the total pressure drop and heat transfer of the extended surfaces considered here.

Ground source heat pumps (GSHPs) are one of the most widespread forms of geothermal energy technology. They utilise the near-constant temperature of the ground below the frost line to achieve energy-efficiencies two or three times that of conventional air-conditioners, consequently allowing a significant offset in electricity demand for space heating and cooling. Relatively mature GSHP markets are established in Europe and North America. GSHP implementation in Australia, however, is limited, due to high capital price, uncertainties regarding optimum designs for the Australian climate, and limited consumer confidence in the technology. Existing GSHP design standards developed in the Northern Hemisphere are likely to lead to suboptimal performance in Australia where demand might be much more cooling-dominated. There is an urgent need to develop Australia’s own GSHP system optimisation principles on top of the industry standards to provide confidence to bring the GSHP market out of its infancy. To assist in this, the Queensland Geothermal Energy Centre of Excellence (QGECE) has commissioned a fully instrumented GSHP experimental facility in Gatton, Australia, as a publically-accessible demonstration of the technology and a platform for systematic studies of GSHPs, including optimisation of design and operations. This paper presents a brief review on current GSHP use in Australia, the technical details of the Gatton GSHP facility, and an analysis on the observed cooling performance of this facility to date.

BackgroundThe coronavirus disease 2019 (COVID-19) pandemic has caused worse health outcomes among elderly populations with specific pre-existing medical conditions and chronic illnesses. There are limited data on health outcomes of hospitalized Parkinson's disease (PD) individuals infected with COVID-19.ObjectivesTo determine clinical characteristics and outcomes in hospitalized PD individuals infected with COVID-19.MethodsIndividuals admitted to NewYork-Presbyterian with a diagnosis of PD were retrospectively identified using an electronic medical record system. Clinical characteristics and mortality were abstracted.ResultsTwenty-five individuals with PD, mostly male (76%) with a median age of 82 years (IQR 73-88 years), were hospitalized for COVID-19 infection. A total of 80% of individuals had mid-stage to advanced PD (Hoehn and Yahr 3-5) and 80% were on symptomatic pharmacologic therapy, most commonly levodopa (72%). The most common comorbidities were hypertension (72%) and mild cognitive impairment or dementia (48%). A total of 44% and 12% of individuals presented with altered mental status and falls, respectively. Mortality rate was 32% compared to 26% for age-matched controls (P = 0.743). Individuals who died were more likely to have encephalopathy during their admission (88% vs. 35%; P

Background and purposeMechanical thrombectomy helps prevent disability in patients with acute ischemic stroke involving occlusion of a large cerebral vessel. Thrombectomy requires procedural expertise and not all hospitals have the staff to perform this intervention. Few population-wide data exist regarding access to mechanical thrombectomy.MethodsWe examined access to thrombectomy for ischemic stroke using discharge data from calendar years 2016 to 2018 from all nonfederal emergency departments and acute care hospitals across 11 US states encompassing 80 million residents. Facilities were classified as hubs if they performed mechanical thrombectomy, gateways if they transferred patients who ultimately underwent mechanical thrombectomy, and gaps otherwise. We used standard descriptive statistics and unadjusted logistic regression models in our primary analyses.ResultsAmong 205 681 patients with ischemic stroke, 100 139 (48.7% [95% CI, 48.5%–48.9%]) initially received care at a thrombectomy hub, 72 534 (35.3% [95% CI, 35.1%–35.5%]) at a thrombectomy gateway, and 33 008 (16.0% [95% CI, 15.9%–16.2%]) at a thrombectomy gap. Patients who initially received care at thrombectomy gateways were substantially less likely to ultimately undergo thrombectomy than patients who initially received care at thrombectomy hubs (odds ratio, 0.27 [95% CI, 0.25–0.28]). Rural patients had particularly limited access: 27.7% (95% CI, 26.9%–28.6%) of such patients initially received care at hubs versus 69.5% (95% CI, 69.1%–69.9%) of urban patients. For 93.8% (95% CI, 93.6%–94.0%) of patients with stroke at gateways, their initial facility was capable of delivering intravenous thrombolysis, compared with 76.3% (95% CI, 75.8%–76.7%) of patients at gaps. Our findings were unchanged in models adjusted for demographics and comorbidities and persisted across multiple sensitivity analyses, including analyses adjusting for estimated stroke severity.ConclusionsWe found that a substantial proportion of patients with ischemic stroke across the United States lacked access to thrombectomy even after accounting for interhospital transfers. US systems of stroke care require further development to optimize thrombectomy access.

Background Atrial fibrillation/flutter (AF) after transient ischemic attack (TIA) has not been well studied. We compared the likelihood of new AF diagnosis after ischemic stroke versus TIA. Methods and Results The POINT (Platelet-Oriented Inhibition in New TIA and Minor Ischemic Stroke) trial enrolled adults within 12 hours of minor ischemic stroke or high-risk TIA. Our exposure was index event type (ischemic stroke versus TIA). The primary analysis used the original trial definition of TIA (resolution of symptoms/signs). In secondary analyses, TIA cases with infarction on neuroimaging were reclassified as strokes. Our primary outcome was a new AF diagnosis, ascertained from adverse event and treatment interruption/discontinuation reports. We calculated C-statistics for variables associated with newly diagnosed AF. We used Kaplan-Meier survival statistics and Cox models adjusted for demographics and vascular risk factors. Excluding 49 subjects with baseline AF, 2746 patients had index stroke and 2086 patients had index TIA. During the 90-day follow-up, 106 patients had newly diagnosed AF. Cumulative risks of AF were 2.7% (95% CI, 2.1%-3.4%) after stroke and 2.0% (95% CI, 1.5%-2.7%) after TIA (P=0.15). After reclassifying index events by neuroimaging, cumulative AF risk was higher after stroke (2.7%; 95% CI, 2.2%-3.4%) than TIA (1.8%; 95% CI, 1.3%-2.5%) (P=0.04). Index event type had negligible predictive utility (C-statistic, 0.54). Conclusions Among patients with cerebral ischemia, the distinction between TIA versus minor stroke did not stratify the risk of subsequent AF diagnosis, implying that patients with TIA should undergo similar heart-rhythm monitoring strategies as patients with ischemic stroke.