Method of Measuring the Vapor Pressure and Concentration of Fluids using VLE and Vibrating Tube Densitometer Apparatuses

This work presents the vapor pressure and concentration measurement of newly discovered environmentally friendly refrigerants 1, 1-difluoroethane (R152a) and 1,1,1,3,3-Pentafluorbutane (R365mfc), besides their mixture. The experimental procedure used in this work was a VLE recirculation type apparatus in which the liquid phase is circulating around the equilibrium cell. Special attention was given to enable a highly accurate vapor pressure measurement up to maximum pressure of 25 bar. The liquid sampling method was perfected through the use of quick plug valves at the circulation loop of the VLE apparatus. This approach has a great effect in solving the problems of changing the volume of the fluids inside the equilibrium cell, since the sampling unit needs a minimum amount of fluid to be sampled. Moreover a new method for measuring the concentration of this mixture through using a vibrating tube densitometer apparatus (DMA-HPM) has been realized. This apparatus was able to supply data in the temperature range of -10 to 200 °C and pressure of 0 to 1400 bar, with an uncertainty of 0.1%. The experimental data was validated using the Volume Translated Peng Robinson Equation of State and high precision fundamental equations of state by McLinden from National Institute of Standard and Technology (NIST). Other models such as Modified Huron Vidal, Wong Sandler, Lee Kesler and Hoffman Florin have been verified. Amongst all the models, McLinden et.al model achieved vapor pressure deviations of less than 0.073% for R365mfc.The concentration deviations reached -3.1%,-9.8% for a composition of 33.6% R152a and 44.1% R365mfc respectively. The deviations of VTPR and VTPR-MHV2 have led to similar results data in the pure fluids and the mixture respectively.

Density of the Refrigerant Fluids of R365mfc and R152a: Measurement and Prediction

This work presents the density of new environmentally friendly refrigerants 1,1-difluoroethane (R152a) and 1,1,1,3,3-Pentafluorbutane (R365mfc) in their pure fluid and mixture. The density is covered in the temperature range of -10-450C and the pressure range of p=0.65-10.47 bar. The density is measured by a vibrating-tube densitometer (DMA-HPM) manufactured by Anton Paar. The apparatus supplies data in the temperature range of -10°C to 200 °C and a pressure range of 0 to 1400 bar, with an uncertainty of 0.1%. The experimental data is validated using the ‘Volume Translated Peng Robinson Equation of State’ and high precision fundamental equations of state by Outcalt and McLinden from the National Institute of Standard and Technology (NIST). Outcalt and McLinden model achieve deviations less than 0.56% for R365mfc and 0.51% for R152a. The deviations of VTPR are within 2.5% and 15% in the pure fluid and mixture respectively.

Regenerative Gas Turbine Power Plant: Performance & Evaluation

In this work, comprehensive operational and conceptual design basics of the Regenerative Gas Turbine were studied and applied to the Khartoum North Thermal Power Station, Sudan, which has a total power of 187MW. The analysis and results of this work were executed using the Engineering Equation Solver.The results show that, the increasing the effectiveness of the regenerative cycle increased the thermal efficiency. However, there is a turning point of compressor inlet temperature, after which the further increase of temperature and regenerator effectiveness will lead to decline in the thermal efficiency of the cycle. At lower regeneration and moderate regenerator effectiveness, the increase in compression ratio leads to an increase in thermal efficiency of the cycle. At the highest values of regeneration effectiveness, the increase in compression ratios reduced the thermal efficiency of the cycle. The results revealed that regeneration is more effective at lower pressure ratios, ambient temperatures, and low minimum (compressor) to maximum (combustor) temperature ratios. An increase in regeneration effectiveness decreases the specific fuel consumption for lower and moderate compression ratios. At higher compression ratios, increasing regenerator effectiveness leads to an increase in the specific fuel consumption (SFC) of the cycle. At low and moderate compressor inlet temperature, increasing the regenerator effectiveness decreases fuel demand in the combustor, which reflects in decreasing the heat rate to the combustor especially at higher regenerative effectiveness (e=95%). As the effectiveness varies between 10-75%, the compressor inlet temperature varies from 200K to 350K and the regenerator exhaust temperature exhibited different profiles according to the conditions of inlet temperature. It was found that power curve declines smoothly due to the increase in irreversibility of regeneration cycle and remains high at higher turbine inlet temperatures. Compressor inlet temperatures between 100-330K increase the regeneration effectiveness varying between 10-95%, resulting a in different profile of the combustor inlet temperature. The mass flow rate of the fuel in the combustor decreases with increasing regeneration effectiveness at lower compressor inlet temperatures. At higher inlet temperatures, the fuel flow rate will gradually increase with the regeneration effectiveness due increasing irreversibilities of the regenerator. For a compression ratio of 15, the fuel mass flow rate reaches the lowest value of (6.30 kg/sec) at the lowest ambient temperature of 200 K and a regenerative effectiveness of 95%. The increase of the lower heating value (LHV) leads to a gradual increase in the thermal efficiency of the regenerative gas turbine (RGT), due to increasing cycle power and combustor capacity. The results concluded that the regeneration effectiveness is higher at low and moderate compressor inlet temperatures and compression ratios, through which, avoiding the regenerator’s irreversibility is possible

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Investigation of Biomass Integrated Air Gasification Regenerative Gas Turbine Power Plants

The results show that Wood Chips of Acacia Nilotica trees available in Sudan lands can be successfully used in the gasification process and, on the same basis, as a bio-renewable energy resource. Simulation models were used to characterize the air gasification process integrated with a Regenerative Gas Turbine Unit. The results revealed that at a moisture content of 12%, gasification temperature of 1500 K, pressure of 20 bar, and air-like gasification medium, the biomass gasifier’s flow rate is higher at higher syngas rates. The results verified that there is an optimum ER for each syngas rate, in which the slow growth of the ER revealed the maximum gasifier biomass flow rate. For ER growth at lower levels, the specific fuel consumption (SFC) of the RGT Unit declines sharply from the maximum value reached at 0.27 kg/kW·h at an ER of 5% to the minimum value reached at 0.80 kg/kW·h at an ER of 25% for the lowest gasification temperature of 1000 K. Moreover, ER growths at low levels have a significant effect on the RGT plant’s performance, leading to increased RGT thermal efficiency. The increase in the biomass moisture content led to a sharp decrease in the RGT thermal efficiency. The RGT thermal efficiency remains high at higher gasification pressure. The results revealed that the syngas lower heating value remains high at lower produced syngas rates. At the optimum ER, the H2 mole fraction depicted a value of 1.25%, 0.85% of CO, and 10.50% of CH4 for a lower heating value of 38 MJ/kg syngas. It is shown that the gasification air entered into the gasifier decreases amid the increase in the biomass moisture content. At different syngas rates (3–10 kg/s) and optimum ER, the results predicted that the Wood Chip biomass flow rates decrease when the gasifier efficiency increases. The simulation model revealed that ER growths at lower levels have a significant effect on increasing the power of the RGT plant