Characterisation of metal organic frameworks for adsorption cooling

Silica gel/water adsorption cooling systems suffer from size, performance and cost limitations. Therefore, there is a need for new adsorbent materials that outperform silica gel. Metal organic frameworks (MOFs) are new micro-porous materials that have extraordinary porosity and uniform structure. Due to the lack of published data that characterise MOF/water adsorption, this paper experimentally investigates the adsorption characteristics of HKUST-1 (Cu-BTC (copper benzene-1,3,5-tricarboxylate), C 18H 6Cu 3O 12) and MIL-100 (Fe-BTC (Iron 1,3,5- benzenetricarboxylate), C 9H 3FeO 6) MOFs compared to silica gel RD-2060. The adsorption characteristics of Silica gel RD-2060, HKUST-1 and MIL-100 were determined using an advanced gravimetric dynamic vapour sorption analyser (DVS). Results showed that HKUST-1 performed better than silica gel RD-2060 with an increase of water uptake of 93.2%, which could lead to a considerable increase in refrigerant flow rate, cooling capacity and/or reducing the size of the adsorption system. However, MIL-100 MOF showed reduced water uptake comparable to silica gel RD-2060 for water chilling applications with evaporation at 5 0C. These results highlight the potential of using MOF materials to improve the efficiency of water adsorption cooling systems

Numerical investigation of turbulent flow heat transfer and pressure drop of AL2O3/water nanofluid in helically coiled tubes

Passive convective heat transfer enhancement can be achieved by improving the thermo-physical properties of the working fluid, changing flow geometry or both. This work presents a numerical study to investigate the combined effect of using helical coils and nanofluids on the heat transfer characteristics and pressure losses in turbulent flow regime. The developed computational fluid dynamics models were validated against published experimental data and empirical correlations. Results have shown that combining the effects of alumina (Al2O3) nanoparticles and tube coiling could enhance the heat transfer coefficient by up to 60% compared with that of pure water in straight tube at the same Reynolds number. Also, results showed that the pressure drop in helical coils using Al2O3 nanofluid for volume fraction of 3% was six times that of water in straight tubes (80% of the pressure drop increase is due to nanoparticles addition), while the effect of Reynolds number on the pressure drop penalty factor was found to be insignificant

Investigation of efficient adsorbents using transient analysis of adsorption chillers with Simulink

With the availability of waste heat from various power stations and industrial processes, adsorption cooling systems offer advantages compared to mechanical vapour compression systems. The dynamic modelling of such system is very important as it predicts the system performance with time in terms of bed temperature, pressure, cooling capacity and coefficient of performance. Therefore there is a need for a robust simulation platform that can be used to predict the system dynamic performance under various operating conditions and accommodate design changes efficiently. This work exploits Simulink software capabilities to develop such simulation platform and investigate the effects of using different adsorbent materials and cycle times on cooling capacity and coefficient of performance. Results showed that such platform is very effective in comparative studies. Results showed that water/silica gel produce more cooling capacity compared to ethanol/activated carbon adsorbents at short cycle time, while Maxsorb has better performance at longer cycle time as its cooling capacity increases with adsorption time

Thermal energy storage using metal–organic framework materials

Metal–organic framework (MOF) materials are new adsorbent materials that have high surface area and pore volume and hence high adsorption uptake. The previous exceptional properties make this class of materials have a great potential in many applications like cooling, gas separation and energy storage. However, there is very limited information on the performance of metal–organic framework materials in energy storage applications and their performance compared to conventional adsorbents. This paper aims to present an experimental characterisation of CPO-27(Ni) MOF material for water adsorption and to investigate its viability for energy storage. CPO-27(Ni) (known as MOF-74(Ni)), which is a MOF material that has high water adsorption capabilities of 0.47 gH2O gads−1 and hydrothermally stable and can be supplied in large quantities. Firstly, the material water adsorption isotherms were predicated using Materials Studio software via the material structure information and then compared to the experimentally measured isotherms. The experimentally measured isotherms and kinetics were used to model a double bed adsorption system for energy storage application using Simulink–Matlab software coupled with Nist RefProp thermophysical routines. Finally, the performance of CPO-27(Ni) was then compared with silica gel. The CPO-27(Ni) was found to outperform silica gel at long half cycle time (more than 30 min) at low evaporating temperature making it suitable for energy storage applications. The energy stored in the condenser and the adsorption bed was found to be dependent mostly on the regeneration and the cooling temperatures. The potential of the energy recovered from the adsorption bed can be double the one recovered from the condenser. Also, the energy recovery during condensation and adsorption was found to be independent of the reactor conductance except at small conductance ratio. Finally, the adsorption unit cooling water flow strategy was found to affect the amount of the energy recovered as recirculating the cooling water through the adsorption bed and then condenser was found to decrease the recovered energy from the condenser by 4%

Global and regional prevalence and outcomes of COVID-19 in people living with HIV: A cutting-edge systematic review and meta-analysis

BACKGROUND: The relationship between HIV infection and COVID-19 clinical outcome is uncertain, with conflicting data and hypotheses. We aimed to assess the prevalence and risk of severe COVID-19 and death in people living with HIV (PLWH) on the global and continental level. METHODS: Electronic databases were systematically searched in July 2021. Studies were screened and then extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Narratives were synthesised and data pooled for global and continental prevalence and relative risk of severity and mortality in HIV-infected COVID-19 patients using random-effect model. Risk of bias was assessed using the Newcastle-Ottawa score, Egger’s test and presented as funnel plots. RESULTS: A total of 46 studies were included involving 18,034,947 COVID-19 cases of which 31,269 were PLWH. The global prevalence of PLWH with SARS-CoV-2 infection was 1% (95% CI = 0.9% -1.1%) with the highest prevalence observed in sub-Saharan Africa. The relative risk (RR) of COVID-19 severity was significant only in Africa (RR, 95% CI = 1.14, 1.08 – 1.24) while risk of COVID-19 mortality was 1.53% (95% CI = 1.45 – 2.03) globally. The prevalence of PLWH in COVID-19 cases was significantly low, and the calculated global risk ratio show that HIV infection may be linked with increased COVID-19 death. The between-studies heterogeneity was significantly high while risk of publication bias was not significant. CONCLUSION: There is low prevalence of HIV-SARS-CoV-2 co-infection. HIV infection was linked with severe COVID-19 in Africa and increased risk of death globally

TET-2 up-regulation is associated with the anti-inflammatory action of Vicenin-2

Vicenin-2, a C-glycoside flavone that is present in many plant sources, exerts potent anti-inflammatory effects in a number of cell and animal models of inflammation. Ten-eleven translocation (TET)-2 has recently gained considerable attention due to the role it plays in regulating the inflammasome. We studied the ability of Vicenin-2 (V-2) to regulate a range of lipopolysaccharide (LPS) stimulated inflammatory activities in PMA-differentiated THP-1 cells and human primary mononuclear cells. We also investigated the action of V-2 on the secretion of NLRP3 inflammasome regulated cytokines (IL-1β and IL-18) by ELISA, and determined if V-2 can regulate the expression of NLRP3, IL-10, IL-1Ra and TET-2. The effect of V-2 on NF-κB signalling was investigated by fluorescence microscopy and gene reporter assay. Additionally, the effect of V-2 on LPS-induced phosphorylation of IKB-α was also investigated by Western blot analysis. V-2 down-regulated LPS-induced secretion of proinflammatory cytokines (TNF-α and IL-1β), in both THP-1 and primary mononuclear cells. V-2 also decreased the LPS-stimulated secretion of IL-18 in THP-1 cells. V-2 significantly down-regulated TNF-α induced NF-κB reporter activity in HEK293T transfected cells and attenuated IKB-α phosphorylation in THP-1 cells. V-2 treatment also induced enhanced nuclear staining of the p50 subunit and reduced p65 subunit of NF-κB. V-2 treatment alone increased the expression of anti-inflammatory cytokine, IL-10, and the regulator of the inflammasome; IL-1Ra, in the presence of LPS. V-2 also significantly decreased LPS-induced NLRP3 expression while concomitantly increasing TET-2 expression. This study demonstrates that the anti-inflammatory actions of V-2 are associated not only with increased IL-10 and IL-1Ra expression, but also with TET-2 up-regulation. Further work is required to establish if the effects of V-2 can be definitively linked to TET-2 activity and that these actions are mirrored in a range of relevant cell types