Design of organic Rankine cycles using a non-conventional optimization approach

The organic Rankine cycle is a suitable technology for utilizing low grade heat for electricity production. Compared to the traditional steam Rankine cycle, the organic Rankine cycle is beneficial, since it enables the choice of a working fluid which performs better than steam at low heat input temperatures and at lowpower outputs. Selecting the process layout of the organic Rankine cycle and the working fluid are two key design decisions which are critical for the thermodynamic and economic performance of the cycle. The prevailing approach used in the design and optimization of organic Rankine cycles is to model the heatexchangers by assuming a fixed minimum temperature difference. The objective of this work is to assess the applicability of this conventional optimization approach and a non-conventional optimization approach. In thenon-conventional optimization approach a total UA-value (the product of the overall heat transfer coefficient and the heat transfer area) is assigned to the cycle, while the distribution of this total UA-value to each of the heat exchangers is optimized. Optimizations are carried out for three different marine engine waste heatsources at temperatures ranging from 90 °C to 285 °C. The results suggest that the conventional optimization approach is not suitable for estimating the performance potential when the temperature profiles in the heat exchangers are closely matched. This is exemplified for the fluid MDM where the temperature profile of preheating aligns with the heat source fluid and for the zeotropic mixture R32/R134a where the temperature profile of condensation aligns with the cooling water. Furthermore, the conventional optimization approach shows weaknesses in evaluating the feasibility of using a recuperator, when the expander outlet temperature is high. In these cases the non-conventional optimization approach is the more suited methodology for designing organic Rankine cycles

Prediction of the annual performance of marine organic Rankine cycle power systems

The increasing awareness about the environmental impact of shipping and the increasingly stricter regulations introduced by the International Maritime Organization are driving the development of solutions to reduce the pollutant emissions from ships. While some previous studies focused on the implementation of a specific technology, others considered a wider perspective and investigated the feasibility of the integration of various technologies on board vessels. Among the screened technologies, organic Rankine cycle (ORC) power systems represent a viable solution to utilize the waste heat contained in the main engine exhaust gases to produce additional power for on board use. The installation of ORC power systems on board ships could result in a reduction of the CO2 emissions by 5 – 10 %. Although a number of methods to derive the optimal design of ORC units in marine applications have been proposed, these methods are complex, computationally expensive and require specialist knowledge to be included as part of a general optimization procedure to define the optimal set of technologies to be implemented on board a vessel. This study presents a novel method to predict the performance of ORC units installed on board vessels, based upon the characteristics of the main engine exhaust gases and the ship sailing profile. The method is not computationally intensive, and is therefore suitable to be used in the context of large optimization problems, such as holistic optimization and evaluation of a ship performance given the operational profile, weather and route. The model predicted the annual energy production of two case studies with an accuracy within 4

Comparison of engagement and emotional responses of older and younger adults interacting with 3D cultural heritage artefacts on personal devices

The availability of advanced software and less expensive hardware allows museums to preserve and share artefacts digitally. As a result, museums are frequently making their collections accessible online as interactive, 3D models. This could lead to the unique situation of viewing the digital artefact before the physical artefact. Experiencing artefacts digitally outside of the museum on personal devices may affect the user's ability to emotionally connect to the artefacts. This study examines how two target populations of young adults (18–21 years) and the elderly (65 years and older) responded to seeing cultural heritage artefacts in three different modalities: augmented reality on a tablet, 3D models on a laptop, and then physical artefacts. Specifically, the time spent, enjoyment, and emotional responses were analysed. Results revealed that regardless of age, the digital modalities were enjoyable and encouraged emotional responses. Seeing the physical artefacts after the digital ones did not lessen their enjoyment or emotions felt. These findings aim to provide an insight into the effectiveness of 3D artefacts viewed on personal devices and artefacts shown outside of the museum for encouraging emotional responses from older and younger people

Selection of cooling fluid for an organic Rankine cycle unit recovering heat on a container ship sailing in the Arctic region

As Arctic sea ice coverage declines it is expected that marine traffic could increase in this northern region due to shorter routes. Navigating in the Arctic offers opportunities and challenges for waste heat recovery systems (WHRS). Lower temperatures require larger heating power on board, hence a larger demand for waste heat usage, to cover services and maintaining on board spaces temperatures. However, a lower heat rejection temperature increases the WHRS thermal efficiency. The air temperature for the Arctic route selected is colder than that of the seawater, opening the opportunity of having air as coolant. This paper explores the use of two different coolants, air and seawater, for an organic Rankine cycle (ORC) unit using the available waste heat in the scavenge air system of a container ship navigating in Arctic Circle. Using a two-step single objective optimisation process, detailed models of air and seawater heat exchangers are evaluated as the WHRS condensers. The results suggest that an ORC unit using R1233zd(E) as its working fluid coupled with seawater as its coolant is the preferable option to reduce CO2 emissions. Using the ambient air as the coolant while a less effective option could be cheaper to install

Treatment of acute diverticulitis laparoscopic lavage vs. resection (DILALA): study protocol for a randomised controlled trial

<p>Abstract</p> <p>Background</p> <p>Perforated diverticulitis is a condition associated with substantial morbidity. Recently published reports suggest that laparoscopic lavage has fewer complications and shorter hospital stay. So far no randomised study has published any results.</p> <p>Methods</p> <p>DILALA is a Scandinavian, randomised trial, comparing laparoscopic lavage (LL) to the traditional Hartmann's Procedure (HP). Primary endpoint is the number of re-operations within 12 months. Secondary endpoints consist of mortality, quality of life (QoL), re-admission, health economy assessment and permanent stoma. Patients are included when surgery is required. A laparoscopy is performed and if Hinchey grade III is diagnosed the patient is included and randomised 1:1, to either LL or HP. Patients undergoing LL receive > 3L of saline intraperitoneally, placement of pelvic drain and continued antibiotics. Follow-up is scheduled 6-12 weeks, 6 months and 12 months. A QoL-form is filled out on discharge, 6- and 12 months. Inclusion is set to 80 patients (40+40).</p> <p>Discussion</p> <p>HP is associated with a high rate of complication. Not only does the primary operation entail complications, but also subsequent surgery is associated with a high morbidity. Thus the combined risk of treatment for the patient is high. The aim of the DILALA trial is to evaluate if laparoscopic lavage is a safe, minimally invasive method for patients with perforated diverticulitis Hinchey grade III, resulting in fewer re-operations, decreased morbidity, mortality, costs and increased quality of life.</p> <p>Trial registration</p> <p>British registry (ISRCTN) for clinical trials <a href="http://www.controlled-trials.com/ISRCTN82208287">ISRCTN82208287</a><url>http://www.controlled-trials.com/ISRCTN82208287</url></p

Robot-assisted radical prostatectomy vs laparoscopic and open retropubic radical prostatectomy: functional outcomes 18 months after diagnosis from a national cohort study in England.

BACKGROUND: Robot-assisted radical prostatectomy (RARP) has been rapidly adopted without robust evidence comparing its functional outcomes against laparoscopic radical prostatectomy (LRP) or open retropubic radical prostatectomy (ORP) approaches. This study compared patient-reported functional outcomes following RARP, LRP or ORP. METHODS: All men diagnosed with prostate cancer in England during April - October 2014 who underwent radical prostatectomy were identified from the National Prostate Cancer Audit and mailed a questionnaire 18 months after diagnosis. Group differences in patient-reported sexual, urinary, bowel and hormonal function (EPIC-26 domain scores) and generic health-related quality of life (HRQoL; EQ-5D-5L scores), with adjustment for patient and tumour characteristics, were estimated using linear regression. RESULTS: In all, 2219 men (77.0%) responded; 1310 (59.0%) had RARP, 487 (21.9%) LRP and 422 (19.0%) ORP. RARP was associated with slightly higher adjusted mean EPIC-26 sexual function scores compared with LRP (3·5 point difference; 95% CI: 1.1-5.9, P=0.004) or ORP (4.0 point difference; 95% CI: 1.5-6.5, P=0.002), which did not meet the threshold for a minimal clinically important difference (10-12 points). There were no significant differences in other EPIC-26 domain scores or HRQoL. CONCLUSIONS: It is unlikely that the rapid adoption of RARP in the English NHS has produced substantial improvements in functional outcomes for patients