Thermodynamic analysis of the partially evaporating trilateral cycle

The potential of Organic Rankine Cycles (ORC) to recover low grade waste heat is well known. The high heat recovery potential is partially attributed to a good match of the temperature profiles between working fluid and waste heat stream in the evaporator. This preferable characteristic is mainly induced by the selection of an appropriate working fluid. However, because of the constant temperature evaporation of the working fluid, the heat recovery potential is restricted. In order to overcome this limitation the trilateral cycle (TLC) has been investigated. A Trilateral cycle (also called Triangular cycle) is a modified Rankine cycle. The main difference is that the working fluid is not evaporated but only heated to the saturation temperature. Compared to the ORC, the heat carrier stream can be cooled further and the thermal efficiency is lower. In this study the effect of partial evaporation of the working fluid is investigated

Performance potential of ORC architectures for waste heat recovery taking into account design and environmental constraints

The subcritical ORC (SCORC), sometimes with addition of a recuperator, is the de facto state of the art technology in the current market. However architectural changes and operational modifications have the potential to improve the base system. The ORC architectures investigated in this work are: the transcritical ORC (TCORC), the triangular cycle (TLC) and the partial evaporation ORC (PEORC). Assessing the potential of these cycles is a challenging topic and is brought down to two steps. First, the expected thermodynamic improvement is quantified by optimizing the second law efficiency. Secondly, the influences of technical constraints concerning volumetric expanders are investigated. In the first step, simple regression models are formulated based on an extensive set of boundary conditions. In addition a subset of environmentally friendly working fluids is separately analysed. In the second step, two cases are investigated with the help of a multi-objective optimization technique. The results of this optimization are compared with the first step. As such the effect of each design decision is quantified and analysed, making the results of this work especially interesting for manufacturers of ORC systems

Deformation analysis of the main components in a single Screw compressor

The single screw compressor is used in many fields such as air compression, chemical industry and refrigeration. During operation, different gas pressures and temperatures applied on the components can cause different degrees of deformation, which leads to a difference between the thermally induced clearance and the designed clearance. However, limited research about clearance design is reported. In this paper, a temperature measurement instrument and a convective heat transfer model were described and used to establish the temperature of a single screw air compressor’s casing, screw rotor and star wheel. 3-D models of these three main components were built. The gas force deformation, thermal-structure deformation and thermal-force coupling deformation were carried out by using a finite element simulation method. Results show that the clearance between the bottom of the groove and the top of star wheel is reduced by 0.066mm, the clearance between the side of groove and the star wheel is reduced by 0.015mm, and the clearance between the cylinder and the rotor is reduced by 0.01mm. It is suggested that these deformations should be taken into account during the design of these clearances

Waste heat recovery via organic rankine cycle: results of a era-SME technology transfer project

The main goal of the EraSME project “Waste heat recovery via an Organic Rankine Cycle”, completed by partners Howest (Belgium), Ghent University (Belgium) and University of Applied Sciences Stuttgart (Germany) between 1 January 2010 and 31 December 2012, was to find an entrance in Flanders for the Organic Rankine Cycle (ORC) technology in applications with sufficient amounts of waste heat at high enough temperatures. The project was preceded by a similar study that focused on renewable energy sources. Several tools were developed to aid in the viability assessment, the selection, and the sizing of ORC installations. With these methods, a fast determination of feasibility is possible. The outcome is based on the size, nature and temperature of the waste heat stream as well as the electricity price. An estimate can be given of the net power output, the investment costs and the economic feasibility. The tool is linked to a database of ORC manufacturer specifications. Another objective of the project was to keep track of the evolution in ORC market supply, both commercial and precommercial. We also looked beyond the product line of the main manufacturers. Some ORCs are developed for specific applications. ORC technology was benchmarked against alternatives for waste heat recovery, such as: steam turbines, heat pumps and absorption cooling. ORC in or as a combined heat and power (CHP) system was also examined. A laboratory test unit of 10kWe nominal power was installed during the project, which is now used in further research on dynamic behavior and control. It is still the only ORC demonstration unit in Flanders and has been very instructive in introducing representatives from industry, researchers and students to the technology. A considerable part of the project execution consisted of case studies in response to industrial requests from several sectors. Detailed and concrete feasibility studies allowed us to define the current application area of waste heat recovery ORC in a better way. A knowledge center for waste heat recovery (www.wasteheat.eu) was initiated to consolidate the know-how and to advise potential users

Post-pandemic self-reported mental health of mental healthcare professionals in the Netherlands compared to during the pandemic:An online longitudinal follow-up study

The mental health of professionals was under pressure during- and post-pandemic. Initially, the focus was mainly on the health workers in the hospitals, but over time the pressure shifted to other sectors, including mental health care. An increase in workload and decrease in mental health of healthcare professionals in mental health care can lead to a decrease in the available care capacity. In an earlier online survey of mental health professionals, 1,300 professionals from a large number of mental healthcare institutions were involved. In this study, conducted in September 2021, about half of the respondents reported increased levels of stress. Feelings of anxiety, anger, and sadness were also increasingly experienced due to the COVID-19 pandemic. Furthermore, 4.2% replied that they were considering resigning their jobs. One of the recommendations of this previous study was to monitor these professionals repeatedly to be able to make an estimate of the stress and vision of work during the course of the pandemic and afterwards. Following this recommendation, the online survey was repeated. The aim of the current online longitudinal follow-up study was to re-evaluated mental status of healthcare workers. 510 healthcare workers participated in this follow-up survey. The reported mental health complaints were significantly higher during compared to post-pandemic. Respondents were less able to maintain work/life balance during the pandemic and even reported a shift to work. However, the majority of respondents indicated that they had restored this balance post-pandemic. Moreover, more sick leave was reported post-pandemic than during the pandemic and more frequent absences post-pandemic. This highlights the importance of focusing on resilience over training and career

Results of mental support for health care professionals and mental care during the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) resulted into a global pandemic and continues to thrive until vaccines have been successfully developed and distributed around the world. The outcomes of COVID-19 contaminations range from death to minor health-related complaints. Furthermore, and not less significant, the increasing pressure on local as well as global health care is rising. In The Netherlands but also in other countries, further intensified regulations are introduced in order to contain the second wave of COVID-19, primarily to limit the number contaminations but also to prevent the health care professionals for giving in to the rising pressure on them. The results of the campaign for health care professionals in The Netherlands show that health care professionals are increasingly searching for information regarding psychological symptoms such as feeling of uncertainty, pondering and advice regarding the support of care teams. In this short update, we provide the results of the previous campaign and stress the importance of support after COVID-19 based on these results

Substantial impact of COVID-19 on self-reported mental health of healthcare professionals in the Netherlands

Initially, the COVID-19 pandemic caused a continued pressure on professionals working in hospitals due to the increase of affected patients. At the moment, the pandemic continues but thanks to all kinds of measures (e.g., social distancing) workload seems to decrease at the hospitals. On the contrary, patients with long-lasting symptoms due to COVID-19 infection or the pandemic begin to merge at the mental healthcare institutions in the Netherlands but this also holds true for other countries. Furthermore, healthcare professionals are affected by safety measures such as working from home, which led to an increased feeling of stress and may have led to a misbalance in work and private life. As a result, the question whether healthcare employees in mental healthcare experience impaired mental health remains unclear and chances are fair that mental health problems such as exhaustion and burnout may be prevalent. This study describes an online survey in which mental health amongst mental healthcare professionals is investigated. About 1,300 professionals from a large number of mental healthcare institutions replied the survey. Around 50% of the respondents experienced increased levels of stress. Feelings of anxiety, anger, and sadness were also increasingly experienced due to the COVID-19 pandemic. Furthermore, 4.2% replied that they were considering resigning their jobs which is alarming considering the shortage of healthcare professionals in mental healthcare institutions. The results support the importance of treatment or support of professionals in mental healthcare that experience psychological ailments