Experimental Investigation of Relative Humidity Effect on the Thermal Conductivity of Desiccant Material

Study on effective thermal conductivity (ETC) of desiccant materials is getting attention in the literature in order to optimize the operating parameters of close and open cycle adsorption cooling systems. In addition, it is an important parameter to enhance the performance of adsorption heat pump and adsorption cooling systems (AHP/ACS). Most of the desiccant materials are porous in nature, therefore, results in different ETC at different operating conditions i.e. temperature and humidity. In order to find the more precise performance expression, the combined effect of desiccant porosity, temperature and relative humidity (RH) should be considered. In this regard, many empirical and theoretical models have been presented for the estimation of ETC. Models developed in the literature are characterized by a single value at a particular temperature irrespective of humidity. Hence this study experimentally investigates the relative humidity effect on the thermal conductivity of the commercially available desiccant material i.e. AQSOA-Z05.The levels of RH were investigated in the range of 8% to 100%. The results showed that ETC of oven dry adsorbent material was 0.066 W/mK whereas it increased from 0.067-0.089 W/mK at RH of 8-100%, respectively. The ETC values increase due to the phenomena of pores filling by water vapor adsorption. It also showed that pore filling incorporate the change in the mean free path and it varied from 6.93-0.55μm at RH range 8-100%, respectively. Consequently, an empirical correlation has been presented which can predict the effective thermal conductivity at different levels of RH

Theoretical and Experimental Analysis of Desiccant Air Conditioning System for Storage of Agricultural Products

The study emphasizes on the use of desiccant air conditioning (DAC) system for the storage of agricultural products. The chilling sensitivity of the tropical fruits and vegetables makes this system more promising for their optimal storage. The desiccant air conditioning system assisted by Maisotsenko cycle evaporative cooler is proposed in the study to achieve the latent and sensible load of air conditioning. In this regard, the dehumidification evaluation of the honeycomb like polymer based hydrophilic desiccant blocks are carried out by the means of an open-cycle experimental unit. The representative ideal storage zones of three temperature and relative humidity compatible groups of fruits and vegetables are established on the psychrometric chart on the basis of published data. The ideal DAC cycle analysis is accomplished at low regeneration temperature (55°C) for case-I (T = 31°C; RH = 21%) and case-II (T = 13°C; RH = 70%). The dehumidification analysis of the desiccant blocks recommended the time ratio between regeneration and dehumidification modes as 1:1 and 2:3 for the case-I and case-II respectively. The suggested time ratios ensure the dehumidification of the process air up to 2 g/kg of dry air and 4 g/kg of dry air in case-I and case-II respectively. The COP of the system was calculated as 0.90-0.43 and 0.55-0.25 at 30-90 minutes dehumidification with regeneration heat supplies of 1.7-2.3 kW and 2.5-3.5 kW in case-I and case-II respectively. The promising dehumidification by the desiccant blocks resulted in achieving the latent load itself followed by flat plate heat exchanger and Maisotsenko cycle evaporative cooler to achieve the sensible load. However, in case of high sensible loads hybrid DAC system is being recommended in this study

Performance Evaluation of Heat Pump Cycle using Low GWP Refrigerant Mixtures of HFC-32 and HFO-1123

Hydro-fluorocarbons (HFCs) have been widely used as working fluids (refrigerants) in air-conditioning and refrigeration systems. At the 1997 Kyoto Conference (COP3), a worldwide agreement was obtained to regulate the production and use of HFCs exhibit high global warming potential (GWP). In the above situation, Hydro-fluoro Olefins (HFOs) having extremely low GWP values such as HFO-1234yf, HFO-1234ze(E), HFO-1123, has attracted attentions. In this study, the performance of heat pump cycle using low GWP refrigerant mixtures of HFC-32 and HFO-1123 is evaluated experimentally. The experimental system is a water heat source vapor compression cycle, mainly composed of an inverter-controlled & hermetic-type scroll compressor (cylinder volume: 11 cm3), an oil separator, a double-tube-type condenser (heat transfer tube; inner grooved , OD 9.53 mm, ID 7.53 mm, total length 7.2 m), a liquid receiver, a solenoid expansion valve, and a double-tube-type evaporator (heat transfer tube; inner grooved , OD 9.53 mm, ID 7.53 mm, total length 7.2 m). Tested compositions of mixtures of HFO-32/HFO-1123 are 58/42 mass% (GWP=393) and 42/58 mass% (GWP=285). These mixtures are tested for the heating and the cooling modes. In the heating mode, the heat sink water temperatures at the inlet and outlet of condenser are kept at 20 ˚C and 45 ˚C, respectively, and the heat source water temperatures at the inlet and outlet of evaporator are kept at 15 ˚C and 9 ˚C. Then, the heating load is varied from 1.6 kW to 2.6 kW. Similarly, in the cooling mode, the water temperature at the inlet and outlet are kept at 30 ˚C and 45 ˚C in condenser, and at 20 ˚C and 10 ˚C in evaporator. Then, the cooling load is varied from 1.4 kW to 2.4 kW. The conventional refrigerant R410A is also tested as the reference. In both modes of heating and cooling, the COP of HFO-32/HFO-1123 mixture (58/42 mass%) is almost the same as that of R410A, while the COP of HFO-32/HFO-1123 mixture (42/58 mass%) is a little lower than that of R410A. By analyzing the irreversible loss of the heat pump cycle based on the second low analysis, the losses of both mixtures in condenser and evaporator are slightly smaller than that of R410A, while the losses of both mixtures in compressor are slightly higher than that of R410A. This result reveals that tested mixtures of HFO-32/HFO-1123 are available to use as the alternative of R410A if the design of compressor and heat exchangers are optimized

Optimized Performance of One-Bed Adsorption Cooling System

Adsorption cooling system can be driven by solar energy or waste heat, so it will effectively reduce fossil fuel consumptions when total system is well-designed. On the other hand, the system tends to have a large size, which will be an obstacle to install adsorption cooling systems to small to medium scale cooling demands, such as automobiles, houses, or shops. The study was aiming at the reduction of system size of adsorption cooling systems for refrigeration and air-conditioning applications. To simplify the system, we investigated one-bed configuration of adsorption cooling system. In general, one-bed adsorption cooling system would result in a large temperature fluctuation at chilled water outlet. To overcome that drawback and to maximize the cooling capacity, the cycle time, namely, pre-heating, desorption, pre-cooling, and adsorption times, of one-bed adsorption cooling system was optimized. In case of two-bed adsorption cooling system, two adsorbers operates in reverse phase each other, which means that the degree of freedom for cycle time optimization is two. In case of one-bed adsorption cooling sytem, four processes can be independently optimized. In our study, activated carbon-ethanol pair was chosen as the adsorbent-refrigerant pair because of a high adsorption capacity of activated carbons against ethanol. Using adsorption isotherms and kinetic data of activated carbon-ethanol pair measured by our research group, a lumped parameter model of one-bed adsorption cooling system was developed. The four parameters of cycle time were optimized using global optimization method, and the optimal time settings were effectively found. The results showed the effect of cycle time optimization on the cooling performance of one-bed adsorption cooling system

The Analysis of Binary Fluid Ejector Assisted Solar Desalination System

The proposed desalination technology represents the combined processes of distillation and congelation of seawater. While distilling runs at two-stage, the condensation heat of the distillate vapors is utilized for cold generation in the Binary Fluid Ejector Refrigeration System (BERS). The congelation process is organized with continuous heat recuperation that enables to mark up about 80% of the fresh water, produced by BERS. The system tolerates any type of seawater (30k ≤ TDS ≤ 100k) and operates with solar thermal heat of 338-356F. The integrated binary fluid ejector heat pump doubles the input of thermal energy at 248F, so the overall output fresh water efficiency is 9 times higher compared to the single stage distillation. This technology represents the novel, economically viable, unrivalled approach that is free from disadvantages typical for most of existed desalination systems. The most efficient flat plate vacuum solar collectors are selected for the study of the integrated solar desalination system. Extensive thermodynamic analysis of the system performance and experimental validation of the results are the core research and development efforts. The main component to operate the solar thermal congelation process is BERS using a binary mixture of low-boiling point refrigerants as the driving fluid of the system. The recent research and experimental studies on utilization of the low-boiling point refrigerants in the ejector-based systems resulted in the 30-50% improved efficiency compared to steam-driven ones, however, it only allowed the ejector systems to become competitive with the other types of the low-grade heat operated heat pumps, such as absorption and adsorption technologies. The application of binary fluids in the ejector-based cooling systems has boosted the energy efficiency as much as 80-120% that potentially makes the binary fluid ejector system the most advanced thermally-driven heat pump ever created. The binary fluid application in BERS allows energy losses reduction by decreasing the velocity difference between working and refrigerant fluids. Binary fluid systems unlike single fluid ones perform a power cycle with a working fluid, that consumes relatively less heat, while the reverse cycle is performed by the most efficient refrigerant fluid, which removes 2-3 times more heat from the low temperature source per refrigerant fluid unit mass. It is important to achieve the maximum entrainment ratio and the lowest ratio of the specific cooling capacity to the specific heat consumption. The contact between primary flow and the secondary flow in the ejector is required for kinetic energy and momentum transfer, which results in both fluids mixing and thereafter requires the formed binary fluid separation by the single components. In order to separate the flows, it is necessary to condense high temperature fluid (working fluid) in fractionating condenser, where, as a result of heat and mass transfer, the concentration of working fluid increases in liquid phase and refrigerant fluid - in vapor phase

Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies

We study the effect of primordial isocurvature perturbations on non-Gaussian properties of CMB temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions for the bispectrum and the Minkowski Functionals for CMB temperature fluctuations to describe the non-Gaussianity from isocurvature perturbations. We find that the isocurvature non-Gaussianity in the quadratic isocurvature model, where the isocurvature perturbation S is written as a quadratic function of the Gaussian variable sigma, S=sigma^2-, can give the same signal-to-noise as f_NL=30 even if we impose the current observational limit on the fraction of isocurvature perturbations contained in the primordial power spectrum alpha. We give constraints on isocurvature non-Gaussianity from Minkowski Functionals using WMAP 5-year data. We do not find a significant signal of the isocurvature non-Gaussianity. For the quadratic isocurvature model, we obtain a stringent upper limit on the isocurvature fraction alpha<0.070 (95% CL) for a scale invariant spectrum which is comparable to the limit obtained from the power spectrum.Comment: 13 pages, 5 figures, MNRAS accepte

Evaluating Clinical Genome Sequence Analysis by Watson for Genomics

Background: Oncologists increasingly rely on clinical genome sequencing to pursue effective, molecularly targeted therapies. This study assesses the validity and utility of the artificial intelligence Watson for Genomics (WfG) for analyzing clinical sequencing results.Methods: This study identified patients with solid tumors who participated in in-house genome sequencing projects at a single cancer specialty hospital between April 2013 and October 2016. Targeted genome sequencing results of these patients' tumors, previously analyzed by multidisciplinary specialists at the hospital, were reanalyzed by WfG. This study measures the concordance between the two evaluations.Results: In 198 patients, in-house genome sequencing detected 785 gene mutations, 40 amplifications, and 22 fusions after eliminating single nucleotide polymorphisms. Breast cancer (n = 40) was the most frequent diagnosis in this analysis, followed by gastric cancer (n = 31), and lung cancer (n = 30). Frequently detected single nucleotide variants were found in TP53 (n = 107), BRCA2 (n = 24), and NOTCH2 (n = 23). MYC (n = 10) was the most frequently detected gene amplification, followed by ERBB2 (n = 9) and CCND1 (n = 6). Concordant pathogenic classifications (i.e., pathogenic, benign, or variant of unknown significance) between in-house specialists and WfG included 705 mutations (89.8%; 95% CI, 87.5%−91.8%), 39 amplifications (97.5%; 95% CI, 86.8–99.9%), and 17 fusions (77.3%; 95% CI, 54.6–92.2%). After about 12 months, reanalysis using a more recent version of WfG demonstrated a better concordance rate of 94.5% (95% CI, 92.7–96.0%) for gene mutations. Across the 249 gene alterations determined to be pathogenic by both methods, including mutations, amplifications, and fusions, WfG covered 84.6% (88 of 104) of all targeted therapies that experts proposed and offered an additional 225 therapeutic options.Conclusions: WfG was able to scour large volumes of data from scientific studies and databases to analyze in-house clinical genome sequencing results and demonstrated the potential for application to clinical practice; however, we must train WfG in clinical trial settings

Diffusion-weighted MR imaging in gynecologic cancers

Diffusion-weighted imaging (DWI) reflects changes in proton mobility caused by pathological alterations of tissue cellularity, cellular membrane integrity, extracellular space perfusion, and fluid viscosity. Functional imaging is becoming increasingly important in the evaluation of cancer patients because of the limitations of morphologic imaging. DWI is being applied to the detection and characterization of tumors and the evaluation of treatment response in patients with cancer. The advantages of DWI include its cost-effectiveness and brevity of execution, its complete noninvasiveness, its lack of ionizing radiation, and the fact that it does not require injection of contrast material, thus enabling its use in patients with renal dysfunction. In this article, we describe the clinical application of DWI to gynecological disorders and its diagnostic efficacy therein