Modelling and Simulation of a Flash Tank Vapour Injection Heat Pump in Several Platforms

In this paper, we model a relatively complex flash tank vapour injection heat pump using the physical modelling software EcosimPro. The heat pump was extensively tested in a previous study and a variety of system parameters were made available for validation. Simulation results are compared against measured data as well as against two other platforms: Dymola and Simulink. Startup and step-change transients have been simulated. The discrepancies between the different models are used to highlight some important aspects in conducting dynamic thermo-fluid simulations. In particular, although qualitatively representative trends may be reproduced, there is an unavoidable need to first obtain experimental measurements to improve the accuracy of the simulated parameters

Comparison of Two Object-Oriented Modeling Environments for the Dynamic Simulations of a Residential Heat Pump

Object-oriented physical-modelling platforms greatly facilitate the task of the modelling engineer by abstracting away a lot of the complexity associated with sorting the governing equations and also the nuances of the numerical methods used for solving the differential-algebraic equations (DAEs). For this reason, they have been steadily gaining in popularity in the field of thermofluid simulations. In this study, we compare two platforms of this type: Dymola and EcosimPro. Dymola is a physical modelling environment originally developed at Lund University and now being developed by Dassault Systèmes, and is a commercially available implementation of the open-source physical modelling language Modelica. EcosimPro is a proprietary tool developed by Empresarios Agrupados A.I.E originally for the European Space Agency and now sold to the general public. Both platforms utilise object-oriented modelling paradigms such as multiple inheritance, encapsulation (of behaviour within classes), abstraction (hiding model complexity from the user) and acausal equation handling (equations may be written in any order). We use these platforms to conduct a realistic exercise of modelling and simulating a relatively complex residential heat pump system in both heating and cooling modes and comparing the results against measured data. Component libraries have been prepared in both the platforms for modelling system components. Two-phase flow has been accounted for using slip-ratio based void fraction correlations. In general, the component models have been kept as similar as possible between the two platforms. The heat pump under investigation is a residential, 3-ton unit with a scroll compressor. The cooling mode uses a thermostatic expansion valve (TXV) as the expansion device while the heating mode uses a short-tube orifice. A reversing valve controls the flow direction. The heat pump has been tested under both heating and cooling modes as per ASHRAE’s Standard 116-2010 cyclic test conditions. The measured values have been compared against simulations results from both platforms. The refrigerant pressures and temperatures and the heat exchanger air outlet temperatures are compared. The indoor unit air-side capacity and the compressor power consumption integrated over the on-period are also compared. Additionally, the Seasonal Energy Efficiency Ratio (SEER), the Cooling Load Factor (CLF) and the Cyclic Degradation Coefficient (Cd) are compared which help quantify the performance of the heat pump. Finally, qualitative comparisons of the transients associated with the refrigerant charge migration after shutdown have been made, as this migration is responsible for cycling losses associated with dynamic heat pump operation. The two platforms prove to be similarly capable at simulating an advanced cycle. Both platforms can predict the pressure and temperature transients during the on-off cycling of the heat pump, as well as the performance parameters such as accumulated capacities and the SEER rating. Finally, both ­models predict the simulated charge to be within 80% of the actual charge, which enables a more realistic depiction of system transients

Bariatric Surgery Closure During COVID-19 Lockdown in Italy: The Perspective of Waiting List Candidates

Background: From the beginning of March 2020, lockdown regimens prevented patients with obesity from receiving bariatric surgery. Surgical emergencies and oncological procedures were the only operations allowed in public hospitals. Consequently, patients with morbid obesity were put in a standby situation. With the aim at exploring the viewpoint of our future bariatric surgery patients, we built a questionnaire concerning obesity and COVID-19.Method: A total of 116 bariatric surgery candidates were approached using a telephonic interview during the Italian lockdown.Results: Of the total sample, 73.8% were favorable to regular bariatric surgery execution. Forty percent were concerned about their own health status due to the COVID-19 emergency, and 61.1% were troubled by the temporary closure of the bariatric unit. The majority of the sample were eating more. Forty-five percent and the 27.5% of patients reported a worsening of the emotional state and physical health, respectively. Most of the patients (52.2%) considered themselves more vulnerable to COVID-19, especially individuals with class III obesity. Patients who reported an increased consumption of food were younger (43.44 +/- 12.16 vs. 49.18 +/- 12.66; F = 4.28, p = 0.042). No gender difference emerged.Conclusion: The lockdown had a negative result on Italian patients' psychological well-being and eating habits. The majority of patients would have proceeded with the surgery even during the COVID-19 emergency. Effective management and bariatric surgery should be restarted as soon as possible

Steady-State heat transfer through micro-channels in pressurized He II

The operation of the Large Hadron Collider superconducting magnets for current and high luminosity future applications relies on the cooling provided by helium-permeable cable insulations. These insulations take advantage of a He II micro-channels network constituting an extremely efficient path for heat extraction. In order to provide a fundamental understanding of the underlying thermal mechanisms, an experimental setup was built to investigate heat transport through single He II channels typical of the superconducting cable insulation network, where deviation from the macro-scale theory can appear. Micro-fabrication techniques were exploited to etch the channels down to a depth of ~ 16 μm. The heat transport properties were measured in static pressurized He II and analyzed in terms of the laminar and turbulent He II laws, as well as in terms of the critical heat flux between the two regions

Microchannel cooling for the LHCb VELO Upgrade I

The LHCb VELO Upgrade I, currently being installed for the 2022 start of LHC Run 3, uses silicon microchannel coolers with internally circulating bi-phase \cotwo for thermal control of hybrid pixel modules operating in vacuum. This is the largest scale application of this technology to date. Production of the microchannel coolers was completed in July 2019 and the assembly into cooling structures was completed in September 2021. This paper describes the R\&D path supporting the microchannel production and assembly and the motivation for the design choices. The microchannel coolers have excellent thermal peformance, low and uniform mass, no thermal expansion mismatch with the ASICs and are radiation hard. The fluidic and thermal performance is presented.Comment: 31 pages, 27 figure

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

CMS physics technical design report : Addendum on high density QCD with heavy ions

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