Combined Power, Cooling And Desalination Using Natural Refrigerant Powered By Low-Grade Heat Source

Contemporary facilities experience growing demand of energy-intensive products like cooling, power and fresh water, which turn in results in energy and environmental concerns. The separate production of these intensive products potentially consumes more primary energy compared with combined production (polygeneration). We therefore seek the most sustainable and suitable polygeneration technology. The driving energy source for the polygeneration system is assumed to be low-grade heat available from solar thermal, geothermal, industrial waste heat, etc. The natural refrigerant based ammonia-water absorption system has the potential for more exploration in the field of polygeneration. In the past decades, ammonia-water based Combined Cooling and Power (CCP) systems were experimentally proven with different configurations. It is of great interest to integrate fresh water generation with an existing CCP system; hence, increasing the system output degrees of freedom with higher system potential performance. So far, the majority of existing desalination plants are Multi Stage Flash (MSF) desalination type, while Multi Effect Distillation (MED) technology has prominent advantages relative to MSF with high thermal efficiency, lower number of effects, low pumping power, high heat transfer coefficient, and tube do not contaminate the distillate water. According to the literature review, none of the published research works has investigated the ammonia absorption system for simultaneous cooling, power and fresh water. In this work, a thermodynamic study was conducted for natural refrigerant polygeneration system operated by low-grade heat sources to produce power and cooling output through generated ammonia vapour, with the rejected heat effectively utilized for desalination of salt water though MED with single flash technology. The combined system is the result of integration of absorption refrigeration, Kalina power and MED with single-stage flash desalination cycles. The low-grade heat source energy generates the refrigerant vapour in the generator, which is divided into two parts for power and cooling. The split ratio is used to vary the power and cooling output, based on demand variation. The total heat rejection from the absorber by heat of absorption and condensation heat from the condenser are effectively utilized for desalination through the MED system. The thermodynamic performance of the system is evaluated at the typical operating conditions of heat source, sink and evaporator temperatures of 250°C, 60°C and -10°C respectively for unit mass flow rate of weak solution. The system generates 170 kWth of cooling, 25 kWe of power generation and 950 kWth of rejected heat available for MED flash desalination. The system performance is evaluated through the effective exergy of the combined system, MED flash system performance ratio and power-to-cooling ratio

Nanofluid optical property characterization: towards efficient direct absorption solar collectors

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase

Thermal contact resistance for a CU/G-10CR interface in a cylindrical geometry

A major component of a high-T[sub c] superconductor current lead designed to provide current to low-T[sub c] superconductor magnets is the heat intercept connection, which is a cylindrical structure consisting of an inner Cu disk, a thin-walled G-10CR composite tube, and an outer Cu ring, assembled by a thermal interference fit. It was determined in a previous study that the thermal contact resistance (R[sub c]) between the composite tube and the two Cu pieces contributed a substantial portion of the total thermal resistance between the inner and outer Cu pieces. This report emphasizes the analysis of the data for the third and final design of the heat intercept connection. In particular, it is found that R[sub c] decreases dramatically with increasing heat flux, a result consistent with earlier studies of composite cylinders. However, for the present data, the thermal contact conductance [=1/R{sub c}]varies with the calculated contact pressure with a power-law exponent of approximately 10, as compared to a theoretical value near 1. In addition, the presence of He or N[sub 2] gas substantially reduces R [sub c] even though the contacting surfaces are coated with a thermal grease

Thermal performance analysis of an existing building heating based on a novel active phase change heater

peer reviewedAn active phase change heater is configurated to transform excess electricity at off-peak tariff periods into thermal energy, store and release it at the electricity on-peak tariff periods to accomplish heating demand towards an existing building with marine climate. A reliable numerical model is developed based on phase change heat transfer and convective heat transfer between phase change material (PCM) and indoor air. The objective temperature zone (18—24 °C) is achieved using an event control that is coupled with a heat transfer model. Performance of indoor temperature, phase change characteris- tics and operating model of active phase change heaters during the building heating period are comprehensively evaluated. Results indicate that indoor temperatures are generally within the thermal comfort range under various initial temperatures and air inlet velocities. Start-stop frequencies of PCM system increase while total working times decrease with the augment of air velocity. Liquid fractions of PCM decrease as studied time elapses, and several parallel stages occur owing to intermittent operation of active phase change heaters. Parametric analysis reveals that thermal resistance is determined as the most decisive factor, followed by ambient temperature, PCM melting point, and PCM thermal conductivity. The liquid fraction of PCMs declines to merely 0.074 when thermal resistance increases to 0.4 (m2 oC)/W. In conclusion, the studied results highlight the correlation between building thermal performance and specific heat transfer characteristics of PCM, with substantial benefits to the development of latent heat thermal energy storage available for building energy conservation.11. Sustainable cities and communitie

Application of Machine Learning Algorithms in Predicting Rheological Behavior of BN-diamond/Thermal Oil Hybrid Nanofluids

The use of nanofluids in heat transfer applications has significantly increased in recent times due to their enhanced thermal properties. It is therefore important to investigate the flow behavior and, thus, the rheology of different nanosuspensions to improve heat transfer performance. In this study, the viscosity of a BN-diamond/thermal oil hybrid nanofluid is predicted using four machine learning (ML) algorithms, i.e., random forest (RF), gradient boosting regression (GBR), Gaussian regression (GR) and artificial neural network (ANN), as a function of temperature (25–65 °C), particle concentration (0.2–0.6 wt.%), and shear rate (1–2000 s−1). Six different error matrices were employed to evaluate the performance of these models by providing a comparative analysis. The data were randomly divided into training and testing data. The algorithms were optimized for better prediction of 700 experimental data points. While all ML algorithms produced R2 values greater than 0.99, the most accurate predictions, with minimum error, were obtained by GBR. This study indicates that ML algorithms are highly accurate and reliable for the rheological predictions of nanofluids

Recruitment of multi-segment genomic RNAs by Bluetongue virus requires a preformed RNA network.

How do segmented RNA viruses correctly recruit their genome has yet to be clarified. Bluetongue virus is a double-stranded RNA virus with 10 segments of different sizes, but it assembles its genome in single-stranded form through a series of specific RNA-RNA interactions prior to packaging. In this study, we determined the structure of each BTV transcript, individually and in different combinations, using 2'-hydroxyl acylation analysed by primer extension and mutational profiling (SHAPE-MaP). SHAPE-MaP identified RNA structural changes during complex formation and putative RNA-RNA interaction sites. Our data also revealed a core RNA-complex of smaller segments which serves as the foundation ('anchor') for the assembly of a complete network composed of ten ssRNA segments. The same order of core RNA complex formation was identified in cells transfected with viral RNAs. No viral protein was required for these assembly reactions. Further, substitution mutations in the interacting bases within the core assemblies, altered subsequent segment addition and affected virus replication. These data identify a wholly RNA driven reaction that may offer novel opportunities for designed attenuation or antiviral therapeutics

Fetal response to external mechanical stimuli

Peer Reviewe

BRCA2 polymorphic stop codon K3326X and the risk of breast, prostate, and ovarian cancers

Background: The K3326X variant in BRCA2 (BRCA2*c.9976A&gt;T; p.Lys3326*; rs11571833) has been found to be associated with small increased risks of breast cancer. However, it is not clear to what extent linkage disequilibrium with fully pathogenic mutations might account for this association. There is scant information about the effect of K3326X in other hormone-related cancers. Methods: Using weighted logistic regression, we analyzed data from the large iCOGS study including 76 637 cancer case patients and 83 796 control patients to estimate odds ratios (ORw) and 95% confidence intervals (CIs) for K3326X variant carriers in relation to breast, ovarian, and prostate cancer risks, with weights defined as probability of not having a pathogenic BRCA2 variant. Using Cox proportional hazards modeling, we also examined the associations of K3326X with breast and ovarian cancer risks among 7183 BRCA1 variant carriers. All statistical tests were two-sided. Results: The K3326X variant was associated with breast (ORw = 1.28, 95% CI = 1.17 to 1.40, P = 5.9x10- 6) and invasive ovarian cancer (ORw = 1.26, 95% CI = 1.10 to 1.43, P = 3.8x10-3). These associations were stronger for serous ovarian cancer and for estrogen receptor–negative breast cancer (ORw = 1.46, 95% CI = 1.2 to 1.70, P = 3.4x10-5 and ORw = 1.50, 95% CI = 1.28 to 1.76, P = 4.1x10-5, respectively). For BRCA1 mutation carriers, there was a statistically significant inverse association of the K3326X variant with risk of ovarian cancer (HR = 0.43, 95% CI = 0.22 to 0.84, P = .013) but no association with breast cancer. No association with prostate cancer was observed. Conclusions: Our study provides evidence that the K3326X variant is associated with risk of developing breast and ovarian cancers independent of other pathogenic variants in BRCA2. Further studies are needed to determine the biological mechanism of action responsible for these associations

The impact of donor and recipient common clinical and genetic variation on estimated glomerular filtration rate in a European renal transplant population

Genetic variation across the HLA is known to influence renal‐transplant outcome. However, the impact of genetic variation beyond the HLA is less clear. We tested the association of common genetic variation and clinical characteristics, from both the donor and recipient, with post‐transplant eGFR at different time‐points, out to 5‐years post‐transplantation. We conducted GWAS meta‐analyses across 10,844 donors and recipients from five European ancestry cohorts. We also analysed the impact of polygenic risk scores (PRS), calculated using genetic variants associated with non‐transplant eGFR, on post‐transplant eGFR. PRS calculated using the recipient genotype alone, as well as combined donor and recipient genotypes were significantly associated with eGFR at 1‐year post‐transplant. 32% of the variability in eGFR at 1‐year post‐transplant was explained by our model containing clinical covariates (including weights for death/graft‐failure), principal components and combined donor‐recipient PRS, with 0.3% contributed by the PRS. No individual genetic variant was significantly associated with eGFR post‐transplant in the GWAS. This is the first study to examine PRS, composed of variants that impact kidney function in the general population, in a post‐transplant context. Despite PRS being a significant predictor of eGFR post‐transplant, the effect size of common genetic factors is limited compared to clinical variables

Global Patterns of Prostate Cancer Incidence, Aggressiveness, and Mortality in Men of African Descent

Prostate cancer (CaP) is the leading cancer among men of African descent in the USA, Caribbean, and Sub-Saharan Africa (SSA). The estimated number of CaP deaths in SSA during 2008 was more than five times that among African Americans and is expected to double in Africa by 2030. We summarize publicly available CaP data and collected data from the men of African descent and Carcinoma of the Prostate (MADCaP) Consortium and the African Caribbean Cancer Consortium (AC3) to evaluate CaP incidence and mortality in men of African descent worldwide. CaP incidence and mortality are highest in men of African descent in the USA and the Caribbean. Tumor stage and grade were highest in SSA. We report a higher proportion of T1 stage prostate tumors in countries with greater percent gross domestic product spent on health care and physicians per 100,000 persons. We also observed that regions with a higher proportion of advanced tumors reported lower mortality rates. This finding suggests that CaP is underdiagnosed and/or underreported in SSA men. Nonetheless, CaP incidence and mortality represent a significant public health problem in men of African descent around the world