Reducing global warming potential (GWP) of refrigerants is needed to the decrease of ozone-depleting of refrigeration systems leakages. Refrigerant R1234yf is now used to substitute R134a inside mobile air conditioning systems. Thermodynamic properties of R1234yf are similar to R134a. Also, it has a very low GWP of 4, compared to 1430 for R134a, making it a proper choice for future automobile refrigerants. The purpose of this research is to represent the main operating and performance differences between R1234yf and R134a. Experimental analysis was carried out on the automotive air conditioning system (AACS) with 3 kW nominal capacity, to test and compare the performance of R134a with R1234yf. Experiments were accomplished for both refrigerants in almost the same working conditions and procedure with a range of ambient temperature varied from 26oC to 50oC. Parameters studied were ambient temperature, type of refrigerant in the system at compressor speed 1450 rpm, and internal thermal loads of passenger room. The performance characteristics of the system, including COP and cooling capacity, were studied by changing different parameters. The results show that COP of R134a is higher than R1234yf by 12.6%, while the refrigeration effect of R134a is higher than R1234yf by 25%. This shows that R1234yf is a suitable and good candidate for drop-in replacement of R134a in AACS.
Copper (Cu) is an essential trace element for the efficient functioning of living organisms. Cu can enter the body in different ways, and when it surpasses the range of biological tolerance, it can have negative consequences. The use of different nanoparticles, especially metal oxide nanoparticles, is increasingly being expanded in the fields of industry and biomedical materials. However, the impact of these nanoparticles on human health is still not completely elucidated. This comparative study was conducted to evaluate the impacts of copper oxide nanoparticles (CuO NPs) and copper sulphate (CuSO4 0.5 (H2O)) on infertility and reproductive function in male albino mice BALB/c. Body weight, the weight of male reproductive organs, mal
... Show MoreA recent study compared experimentally the hydraulic and thermal activity of twisted tape inserts for two types, metal foam twisted tape (MFTT) and traditional twisted tape (TTT), in a double pipe heat exchanger. The investigation goal of the innovatively designed MFTT is to enhance the heat transfer process, which provides a higher thermal enhancement factor over those of TTT under the same conditions. Heat transfer activity in terms of Nusselt number (
The current research aims to identify the level of compulsive buying behavior and Histrionic Personality among a sample of primary school teachers for the academic year (2021-2022) and in the light of some variables
(sex, marital status). To measure the Histrionic Personality, the researcher applied two scales to a random stratified sample of (200) male and female teachers. The results showed statistically significant differences in the level of compulsive buying behavior according to the gender variable and in favor of female teachers. There are no statistically significant differences in terms of marital status. There are statistically significant differences in the Histrionic Personality based on gender variables in favor of f
... Show MoreThe research seeks to know the social loafing of kindergarten teachers and their relation to personality traits. In order to achieve the research objectives, the researcher constructed the social loafing scale, which she applied to kindergarten teachers. The scale consists of (22) paragraphs. It has good credibility and stability. The coefficient of stability (85.0) was the retest method and (81.0) Alpha Cronbach equation. In addition, the researcher has adopted (Raymond Cattel) personality traits scale, which has been adapted to the Arab environment (Abdel Rahman and Abu Abada,1998), The scale consists of (39) paragraphs, and enjoys the apparent honesty. The measure of social loafing and the measure of personality traits was applied to
... Show MoreThe process of cognitive representation includes mental activities such as perception, concepts formation and decision making leading to formation of Cognitive representation where the need for Cognition is one of basic humane needs promoting individuals to have more information.
This Study aims to measure the level of Cognitive representation among gifted Schools, the level of need for Cognition among them, recognize statistical Significant differences with Cognitive representation according to gender Variable and recognize the Correlation between Cognitive representation and the need for Cognition among giftel schools . The sample Consists of subsample of mair application one Consisting of( 400) students, noting that the first sampl
The two objectives of the current research are :-
- Uncover the views and opinions of the students of Artistic Education Department about the relation between educational novelty and its relation with visual .
- Identifying the capabilities of the students of artistic education department .
The society of the research is the fourth class students of artistic education department - College of Fine Arts ( 83 students from both sexes ) . It was chosen ( 60 ) students sample of from both sexes by the researcher in order to conduct test upon them .The researcher has adopted descr
... Show MoreThe preparatory phase since it corresponds to adolescence are the most important stages of life , where the individual 's personality to take shape at this stage and start asking questions about the same , trying to discover the positive and negative traits hehas in order to form distinctive character and also is being he have Love Poll For everything that goes on around him.
And attention to cognitive motivation is important for students because the student who owns a motive cognitively looking for self - knowledge with conviction, and learning then be meaningful and lasts long. The motive of knowledge are common in which cognitive components does not mean exclusive knowledge on academic books and research in the narrow borders but a
Periodontitis is one of the most prevalent bacterial diseases affecting man with up to 90% of the global population affected. Its severe form can lead to the tooth loss in 10-15% of the population worldwide. The disease is caused by a dysbiosis of the local microbiota and one organism that contributes to this alteration in the bacterial population is Prophyromonas gingivalis. This organism possesses a range of virulence factors that appear to contribute to its growth and survival at a periodontal site amongst which is its ability to invade oral epithelial cells. Such an invasion strategy provides a means of evasion of host defence mechanisms, persistence at a site and the opportunity for dissemination to other sites in the mouth. However, p
... Show MoreCurrent search aims to identify the creative thinking of the kindergarten teachers and
solving professional problems among kindergarten teachers skills, and whether the level of
creative thinking in solving professional problems, according on marital status years of
service academic achievement of teachers as well as to identify the correlation between the
two variables the current sample consisted of (300) teachers to achieve the objectives of the
stndy , the researcher used two measures, one to measure creative thinking and the other to
measure the solution to the problems of professional kindergarten teachers skills. It has been
shown. validity and reliability of the two measures. The present stndy aims to identif