Refrigerants With Low Environmental Impact For Commercial Refrigeration Systems

New refrigerants with the positive attributes of both high thermal performance and low environmental impact are currently in development. These refrigerants provide high energy efficiency, which coupled with low GWP significantly reduce the total environmental impact compared with current fluids (R404A, R507, R22 and R134a). Properties, and experimental results are compared and discussed for refrigeration applications. Alternative system architectures for refrigeration applications utilizing the beneficial characteristics of these new fluids are also discussed. A holistic analysis approach is used to evaluate the lifetime environmental and operational impact for the refrigerants and systems presented in this study

Low GWP Refrigerants for Air Conditioning Applications

Refrigerants with low environmental impact have been developed as replacements for R22 and R410A in air conditioning applications. L-20 and L-41 have been evaluated in representative residential equipment. This study discusses the performance at high ambient temperatures (warm climate) and potential design changes. In addition, 1233zd and 1234ze have been evaluated as replacements for R123 and R134a in low and medium pressure chiller applications. Theoretical and experimental results are discussed in detail showing the benefits of using these new fluids

Refrigerants with Low Environmental Impact for Refrigeration Applications

New refrigerants with considerable low environmental impact are currently under evaluation by the refrigeration industry. Such refrigerants could be used in place of high global warming fluids like R404A. Among these new fluids are 1234ze, N-13, L-40 and N-40. Initial laboratory evaluations of these refrigerants showed good energy efficiency due to their good thermal properties. These initial evaluations were followed by larger scale (field) trials, refrigerant–oil property measurements, and also material compatibility. This study presents and discusses results of such evaluations, and extends the assessment to LCCP using different refrigeration technologies and refrigerants

Use of Blends in Commercial Refrigeration Systems: Fractionation characteristics and material compatibility of R448A

The development of lower global warming potential (GWP) blends offers an alternative for the widely used high GWP fluids such as R404A. Commercial refrigeration systems for supermarkets are a common example for such systems. These kinds of systems show relatively large refrigerant leakage rates of 15% to 20% per year. The newly developed R404A lower GWP alternatives are zeotropic blends, meaning they show a temperature glide during phase change processes in the evaporator and condenser of the system. Because of the glide, there is a concern within end users that the blend components could separate, or fractionate, during a leak event. Â This paper will describe the results from tests carried out to determine the effect of refrigerant fractionation and its effect on the performance of an actual refrigeration system subject to multiple leak events. The second part of this paper provides characteristics for the solubility and miscibility of R448A with POE oil and results from a material compatibility study of R448A with common materials used in refrigeration equipment

Latest Developments of Low Global Warming Refrigerants for Chillers

This paper will focus on the developments of new molecules that have low global warming potential, high thermal performance, and favorable safety characteristics, to name only a few required characteristics. Several new molecules that have very short atmospheric lifetimes, as well as refrigerant blends utilizing these molecules, have been developed and will be evaluated for use in various types of water chillers ranging from smaller capacity systems that currently use R-410A or R-407C refrigerants to larger centrifugal compressor chillers that have currently used R-134a or R-123. Thermodynamic and system simulations were carried out using low GWP refrigerant properties and compared against the baseline refrigerants. These new LGWP refrigerants show promise in these applications and warrants further development

Low Global Warming Refrigerants For Commercial Refrigeration Systems

New refrigerants with the positive attributes of both high thermal performance and low environmental impact are currently in development. Initial evaluation of these refrigerants in refrigeration systems show good energy efficiency and significant lower global warming impact than current refrigerants. Some of those Low GWP refrigerants are non-azeotropic blends with moderate to high glide; therefore guidance on the use of these blends is needed to achieve the desired good performance and low environmental impact. This study discusses glide effects on the performance and operation of refrigeration systems. Issues related to servicing systems such as fractionation are also discussed. Data is presented using current refrigerants such as R407F and other refrigerant blends currently under development

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London