Normalized Effect Of Condenser Fouling And Refrigerant Charge On Performance Of Vapor Compression Air Conditioning Systems

Several laboratory experiments have studied the effect of faults on vapor compression cycle air-conditioning systems. There has been a particular focus on refrigerant charge variation, which is believed to be quite common in air conditioners, and a lesser focus on heat exchanger fouling. The majority of the published results evaluate the fault effects on particular system operating parameters in one unit. For example, the effect on capacity and efficiency are typically evaluated. The results differ from one study to the next. The current paper summarizes the effects for all of the results available in the literature for condenser fouling and refrigerant charge variation, and provides generalized relationships. The generalizations are provided for ANSI/AHRI 210/240 standard test conditions and are provided separately for fixed orifice and thermostatic expansion valve equipped systems. The level of variation found in the summary shows that for many applications, it is reasonable to the use generalized relationships to estimate the effect of faults on systems that have not been tested in a laboratory

Long-term Product Rating Prediction Based on Users' Short-term Multiple Ratings

Ratings and product reviews could be considered as one of the main features determining the quality of a product in online store systems, especially in deciding whether to place a product as part of an online store's inventory. online vendors are often attracted by product reviews and ratings. However, when the average product rating observed based on a small number of user ratings, the decision maker may not be certain about choosing that product, even if it has a fairly high rate. Long-term rating predictions would help online vendors to identify products and advertise their websites by choosing potential ones. In this paper machine learning approach utilizing linear regression model is used to predict long-term product rate. The model evaluated using the Datasheet of the Amazon Online Store website,1996 to 2014. Keywords: Rating, Long-term Prediction, Machine Learning Algorithm, Linear Regression. DOI: 10.7176/JIEA/9-4-04 Publication date:June 30th 2019

Evaluation The Effect Of Washing On The Heat Transfer Capacity And Air-Side Flow Resistance Of Air Cooled Condensers

Air cooled condensers are commonly used in rooftop units and residential air-conditioners to reject heat outdoors. Airborne particles in the environment, such as dust, grass, leaves, seeds, and anthropogenic agents, can foul the air side of the condensers. Therefore, it is common practice to regularly clean the air side of condensers. Seven fouled wavy fin, and two fouled spiny fin condensers from residential condensing units were collected at the end of their service lives, and examined in the laboratory to study the effect of the fouling on heat transfer capacity and air-side flow resistance. A test apparatus was designed and built to investigate the flow resistance and heat transfer of these coils before and after cleaning. After testing each condenser in the fouled condition, the fouling material was collected and its mass was measured. Then, the coil was washed with water and tested again in the test apparatus. Finally, to investigate the effectiveness of commercial detergents, these coils were cleaned with a detergent and tested again. Surprisingly, the results show that the effect of washing on the heat transfer capacity of the coil is very small, and in some cases, the fouled condenser performed better before cleaning than afterwards. Similarly, cleaning the units with detergent had negligible differences compared with the effects from cleaning with water only, and in some cases, the detergent caused performance degradation in terms of flow resistance and heat transfer

Influence of different concentrations of two chemical chaperones on human islet amyloid polypeptide folding under experimental conditions

It has been implicated that type 2 diabetes mellitus is a conformational disease because amylin, a peptide produced by beta cell, undergoes an alteration in the native formation followed by self-aggregation and deposition. Amyloidogenesis causes destruction of pancreatic beta-cells. The subsequent lack of insulin leads to increased blood glucose. The main aim of this study was to investigate whether two chemical chaperones named glycerol and spermine vary islet amyloid polypeptide folding under near-physiological circumstances. For this purpose, fluorescent method was used with LS55 spectrofluorometer instrument. Results obtained from in vitro study show that after 240 h incubation by shaker incubator in 37°C, glycerol had contradictory effects on amylin folding and these effects were glycerol concentration dependent. Glycerol with concentration of 24% had the most inhibitory effect but 40 to 50% promoted amylin misfolding significantly (p<0.05). The obtained data also demonstrate that spermine with concentrations of 40, 50 and 60 μM had stimulatory effects on formation of beta-amyloid sheet significantly (p<0.05). It is concluded that amylin misfolding and cytotoxicity to beta-cells might be glycerol dose-dependent in diabetic patients.Key words: Chemical chaperones, islet amyloid polypeptide, diabetes mellitus, conformational disease

Incidence Rate and Risk Factors of Radial Artery Spasm during Transradial Coronary Angiography

Background: Radial artery spasm (RAS) is one of the most common complications of radial coronary angiography. Several demographic and clinical factors increase the risk of RAS in this procedure. We aimed to evaluate the effect of various risk factors on the incidence and severity of RAS in radial coronary angiography.  Methods: This cross-sectional study was performed on 120 patients who were randomly selected from candidates referred to Shahid Modarres Educational Medical Center for coronary angiography by the radial method. After angiography, radial arteriography was performed to diagnose spasms. The association of some demographic and clinical factors with the incidence and severity of RAS was evaluated. Results: 35 of the 120 patients (29.16%) developed RAS during angiography. Shorter height, shorter radius bone length, less radial artery diameter, longer procedure length, diabetes mellitus, more catheters used, and female sex were significantly associated with higher incidence. The predictive power of these factors for the occurrence of spasms was very good with AUC=0.88. Age, shorter height, higher body mass index, smaller radial artery diameter, longer procedure time, diabetes mellitus, failure of initial effort for puncture, number of catheters used, and female sex were significantly associated with the severity of spasms. Conclusions: The incidence or severity of spasms during the procedure can be reduced by examining the available risk factors for every patient before deciding to perform angiography

The effect of geometrical characteristics of wavy strip turbulator and thermodynamic properties of fluid on exergy loss and heat transfer in a tube in tube heat exchanger

The present work conducts an experimental investigation into the influence of flow, thermodynamic and geometrical characteristics of the wavy strip on exergy loss and dimensionless exergy loss in a tube in tube heat exchanger. The working fluid is water with hot water passing the inner tube and cold water passing annulus. Wavy strips with four different angles and three widths were investigated experimentally. The result of exergy loss and dimensionless exergy loss for various conditions is presented and on the basis of curve fitting, three empirical correlations are suggested to predict dimensionless exergy loss in a double tube heat exchanger.https://www.tandfonline.com/loi/ueht202019-10-02hj2019Mechanical and Aeronautical Engineerin

Isolation and Identification of Fungal Endophytes of the Cowpea in Khuzestan Province

Introduction: Endophytes are microorganisms that colonize internal tissues of plants without causing obvious symptoms. This study was conducted to isolate and identify endophytic fungi of the cowpea in Khuzestan province. Materials and methods: During 2016, eight healthy samples of the cowpea plants were collected from the important areas under cultivation in the northern Khuzestan province. The small parts of the roots, stems, leaves and pods were deeply surface sterilized for each samples and plated on Potato-Dextrose-Agar. Sixty fungal isolates obtained in this study were purified by single spore method. Based on morphological characteristics, 21 out of 60 isolates were selected for molecular study. The isolates were grown in Potato-Dextrose-Broth and mycelial biomass was recovered by passing through filter paper. DNA extraction was performed using a phenol- and chloroform- based organic method. The parts of the nrRNA gene (ITS and 28S-D1/D2 regions) were amplified using appropriate primer pair and then sequenced. Results: The isolates were analyzedon the basis of morphological characteristics in combination with BlASTn search algorithm and ITS sequence-based phylogeny. Accordingly, the isolates were identified as follows: Alternaria destruens, Alternaria sp., Curvularia mosaddeghii, Curvularia sp., Fusarium chlamydosporum, F. nygamai, F. falciforme, F. proliferatum, Fusarium sp. Macrophomina phaseolina and Penicillium oxalicum. Discussion and conclusion: Alternaria, Fusarium and Curvularia genera were the most abundant fungal endophytes into cowpea plants, growing in warm climate of the Khuzestan Province. To the best of our knowledge, this is the first study to report endophytic growth of A. destruens, Alternaria sp., M. phaseolina, F. chlamydosporum, F. nygamai, F. falciforme, F. proliferatum and P. oxalicum within cowpea plants

Modelling and multi-objective optimisation of heat transfer characteristics and pressure drop of nanofluids in microtubes

Please read abstract in the article.South African CSIR/DSTCentre for High Performance Computing (CHPC)http://www.tandfonline.com/loi/uhte202021-10-09hj2021Mechanical and Aeronautical Engineerin

Electrical conductivity and pH modelling of magnesium oxide–ethylene glycol nanofluids

Nanofluids as new composite fluids have found their place as one of the attractive research areas. In recent years, research has increased on using nanofluids as alternative heat transfer fluids to improve the efficiency of thermal systems without increasing their size. Therefore, the examination and approval of different novel modelling techniques on nanofluid properties have made progress in this area. Stability of the nanofluids is still an important concern. Research studies on nanofluids have indicated that electrical conductivity and pH are two important properties that have key roles in the stability of the nanofluid. In the present work, three different sizes of magnesium oxide (MgO) nanoparticles of 20, 40 and 100 nm at different volume fractions up to 3% of the base fluid of ethylene glycol (EG) were studied for pH and electrical conductivity modelling. The temperature of the nanofluids was between 20 and 70◦C for modelling. A genetic algorithm polynomial neural network hybrid system and an adaptive neuro-fuzzy inference system approach have been utilized to predict the pH and the electrical conductivity of MgO–EG nanofluids based on an experimental data set.http://www.ias.ac.in/matersci/index.htmlhttp://link.springer.com/journal/12034am2020Mechanical and Aeronautical Engineerin