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.
Praise be to God, we praise Him, we seek His help, we seek His forgiveness, and we seek refuge in God from the evils of ourselves and our bad deeds. . The marriage contract, like other contracts, gives rise to reciprocal rights and duties that bind both the husband and the wife, pursuant to the principle of balance, equivalence, and the equality of the parties to the contract on which every contract is based. . That is, women have rights over men similar to what men have over women, or that the basis for estimating these rights and duties is custom based on the nature of both men and women. The Iraqi Personal Status Law stipulates all the financial rights that the wife is entitled to from her husband: namely, the dowry and alimony. As fo
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First: the problem of research and its importance
The teacher's success in facilitating the students' learning and growth according to the educational and educational goals set out, he must identify the problems of discipline of students in the classroom in terms of sources and reasons and types and methods of prevention and treatment and the teacher to remember that success in his teaching and instruction is not completed more fully once he has the information And knowledge of the subject of the lesson, but must understand the dynamics of the group (class group) and master the skills of classroom management, su
... Show MoreThe article approaches the characteristics of Russian literature in the time of Khrushchev or the "thaw" period a very short period of Soviet history, characterized by the easing of the dictatorship of power and relaxation in various areas of people's lives. The interest in the research is focused on the importance of interpreting the family portrait in a short but distinct period in the development of Russian/Soviet literature. The research material is the story of Sholokhov's “The Fate of Man” 1956, the story of Panova “Serioga” 1955, and Abramov’s story “Fatherless” 1961. В статье рассматриваются особенности художественной литературы периода хруще
... Show MoreThis paper provides an attempt for modeling rate of penetration (ROP) for an Iraqi oil field with aid of mud logging data. Data of Umm Radhuma formation was selected for this modeling. These data include weight on bit, rotary speed, flow rate and mud density. A statistical approach was applied on these data for improving rate of penetration modeling. As result, an empirical linear ROP model has been developed with good fitness when compared with actual data. Also, a nonlinear regression analysis of different forms was attempted, and the results showed that the power model has good predicting capability with respect to other forms.
Excessive intake of fluoride, mainly through drinking water is a serious health hazard affecting humans worldwide. In this study, the defluoridation capacities of locally available raw waste beef bones have been estimated. Several experimental parameters including contact time, pH, bone dose, fluoride initial concentration, bone grains size, agitation rate, and the effect of co-existence of anions in actual samples of wastewater were studied for fluoride removal from aqueous solutions. Results indicated excellent fluoride removal effeciency up to 99.7% at fluoride initial concentration of 10 mg F/L and 120 min contact time. Maximum fluoride uptake was obtained at neutral pH range 6-7. Fluoride removal kinetic was well described by the ps
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