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.
Autorías: Suhair Meteab Munaf, Ali Abdulateef Ali, Mohannad Salman Dawood. Localización: Revista iberoamericana de psicología del ejercicio y el deporte. Nº. 4, 2022. Artículo de Revista en Dialnet.
BACKGROUND: Acute coronary syndrome (ACS) is the clinical manifestation of acutely diminished coronary arterial blood supply. The rate of increase of intraventricular pressure during isovolumetric contraction (left ventricular dP/dt) represents the rate of change of pressure during ejection. OBJECTIVE: The aim of this study is to evaluate the usefulness of the rate of increase of intraventricular pressure during isovolumetric contraction (dP/dt) in assessment of left ventricular function in patients with acute coronary syndrome and its relation to certain clinical and echocardiographic features. PATIENTS AND METHODS: The study is a cross sectional study including 50 patients with an established diagnosis of acute coronary syndrome. The
... Show MoreThis study investigates the requirements of total quality management (TQM) and the determinants affecting its application in Al-Zaman newspaper, one of Iraq’s leading private press institutions. The research employed a survey methodology, using a structured questionnaire administered to 30 participants representing journalistic, administrative, and technical staff. Five TQM dimensions, each measured through four indicators, were assessed to capture the perceptions of employees regarding the availability and effectiveness of quality practices. Data were analyzed using the Statistical Package for the Social Sciences (SPSS). The results revealed that while senior management at Al-Zaman demonstrates formal support for TQM, there is a
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This study aims at clarifying the current performance appraisal system in government units and the extent to which they contribute to the development of the performance of these units by evaluating and measuring the performance of these units on an ongoing basis to subject their services to an assessment and measurement process in order to improve the efficiency of these units to reach their objectives efficiently and effectively. (Iraqi hospitals) by trying to determine the possibility of the government accounting system in the process of evaluating performance, through the comparison of financial performance for successive years and different hospitals using the financial and non-financial model of the evaluati
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This study aimed to choose top stocks through technical analysis tools specially the indicator called (ratio of William index), and test the ability of technical analysis tools in building a portfolio of shares efficient in comparison with the market portfolio. These one technical tools were used for building one portfolios in 21 companies on specific preview conditions and choose 10 companies for the period from (March 2015) to (June 2017). Applied results of the research showed that Portfolio yield for companies selected according to the ratio of William index indicator (0.0406) that
... Show MoreIraq's oil industry has been passed in different periods , began with domination of Western companies to invest in Iraqi oil at twenties of the last century , through the process of nationalization of the shares of those companies , beginning of the seventies , and ending with the new policies adopted by the government recently, which was contracting with international companies to develop the oil industry , because of what the outcome of the oil industry from a decline in artistic and physical ability as a result to the conditions of war and embargo imposed on Iraq before 2003.
The Iraqi government has introduced licensing of a contract to
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The research aims to identify the strategic leadership and its role in activating the Organisational Performance, which is an analytical study of the views of the heads of scientific departments at General Authority of groundwater researcher's quest focused towards building a theoretical framework suitable for strategic leadership and performance Organisational and itُs dimensions.To achieve the aims of the research is designed to identify the researcher included (35) items to collect the raw data from the research sample consisting of 33 of the heads of departments. Data was collected by questionnaire, field visits, interviews and some official documents to complete the search data. It has also been used a numb
... Show MoreThis study was conducted for the purpose of exploring the relationship between positive thinking and academic achievement in art history. And it relates to the student’s personality, intelligence, abilities and economic and social level. The sample of the study consisted of (40) male and female students from the first stage students - Department of Art Education in the Faculty of Fine Arts / Morning Study, A positive thinking questionnaire was applied to them, and the study found that there is no positive relationship between positive thinking and academic achievement in art history.
Research Summary
This research deals with the history of the founding of one of the most prominent religious schools in Iraqi Kurdistan and its scientific and cognitive contributions that lasted for more than a century, which is the “Biyara” school, where it was a large scientific institution from which distinguished scholars graduated who served Islam and Muslims in Iraq and neighboring countries, and played an important role in teaching Mental and transport sciences and the preservation of the Arabic language in Iraqi Kurdistan. The history of the founding of this school goes back to the year 1037 AH, at the hands of its founder, Sheikh Oma
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