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.
This paper demonstrates an experimental and numerical study aimed at comparing the influence of openings of different configurations on the flexural behavior of reinforced concrete gable roof beams. The experimental program consisted of testing six simply supported gable beams subjected to mid-point concentrated load. The variable which has been investigated in this work was opening's configuration (quadrilateral or circular) with the same upper and lower chords depth. The results indicate improvement in the beams’ flexural behavior when circular openings were used compared with that of quadrilateral openings, represented by an increase in ultimate load capacity and a decrease in deflection at the service limit. Also, there was an
... Show MoreThis study was aimed to develop an optimized Dy determination method using differential pulse voltammetry (DPV). The Plackett-Burman (PB) experimental design was used to select significant factors that affect the electrical current response, which were further optimized using the response surface method-central composite design (RSM-CCD). The type of electrolyte solution and amplitude modulation were found as two most significant factors, among the nine factors tested, which enhance the current response based on PB design. Further optimization using RSM-CCD shows that the optimum values for the tw
... Show MoreExperimental measurements of viscosity and thermal conductivity of single layer of graphene . based DI-water nanofluid are performed as a function of concentrations (0.1-1wt%) and temperatures between (5 to 35ºC). The result reveals that the thermal conductivity of GNPs nanofluids was increased with increasing the nanoparticle weight fraction concentration and temperature, while the maximum enhancement was about 22% for concentration of 1 wt.% at
35ºC. These experimental results were compared with some theoretical models and a good agreement between Nan’s model and the experimental results was observed. The viscosity of the graphene nanofluid displays Newtonian and Non-Newtonian behaviors with respect to nanoparticles concen
Abstract: Lymphoproliferative Disorders (LPDs) are a group of neoplasms affecting various cells within lymphoid system. Each type has different treatment a..70619
Objective: To assess the clinical learning environment and clinical training for students' in maternal and child
health nursing.
Methodology: A descriptive study was conducted on non probability sample (purposive) of (175) students' in
Nursing College/ University of Baghdad for the period of June 19th to July 18th 2013. A questionnaire was used as a
tool of data collection to fulfill with objective of the study and consisted of three parts, including demographic,
clinical learning environment and clinical training for students' in maternal and child health nursing. Descriptive
statistical analyses were used to analyze the data.
Results: The results of the study revealed that the 65.1% of student at age which ranged b
God, may He be glorified and exalted be He, has given every human being the right to life and a dignified life, and has warned against transgression against any of its sanctities without a legitimate right. No one, regardless of his status or authority, can deprive a person of his rights that the Sharia came to preserve, and whoever does that has declared all people to war, as all humanity is in solidarity. In raising the hand that is simplified to harm a person and oppress him unjustly and exalted in the land.
If this is the case, the Sharia came to establish the right of people, groups and individuals, to defend their sanctities, preserve their security, recover their usurped rights, repel the aggression of the aggressors, and oppre
This day, we see the Significant role that social media platforms play, it plays a vital role in shaping the Social, political, and economic awareness of individuals. The Iraqi Society, which is experiencing rapid cultural and social transformations, is considered a fertile ground for social media and its influences, whether negative or positive. Research and studies indicate that the negative use of social media will lead to weaking of the sense of belonging and citizenship among members of Iraqi society. This, in turn, threatens moral and educational values, increases feelings of family estrangement, and leads to social isolation. On the contrary, if social is used correctly, it can significantly contribute to enhancing educational values
... Show MoreThe research is conducted on target of investigating the role of growth strategy via diversification in value maximization of a firm in terms of controversies literatures had witnessed. Using a descriptive approach for analyzing and verifying the harmony of variables of research and their conceptualized logic , it could be reached to many conclusions agreed in their essence upon that the related diversification has the major role in value maximization of a firm and the wealth of its owners .
Abstract:
Due to the importance of technology and the accompanying changes of the environment affecting companies that use the technology mainly in their work, especially as most companies live in an unstable dynamic environment, which motivated the researchers to choose the International Company for smart card (Keycard) as a field of research and find ways to them to face Those changes.
The problem of the study was "limited attention to the components of technological change", which included research and development, innovation and information technology, which had an impact on the design decisions of the process (process selection, cust
... Show MoreThe almighty Al-Bari imposed on Muslims easy and accessible worshipers for every individual who is eligible to commission, so whoever performed it rightfully, God rewarded it with the best reward. From the Muslim, the Almighty made the Almighty to the types of acts of worship and acts of righteousness as a reason for the remission of sins that were advanced and late, so I chose a topic (from the hadiths of righteous deeds mentioned in the atonement of sins) as a research drawn from the master’s thesis called (the hadiths of the atoners of sins that were presented and delayed - An analytical study- ), And collect in this research kinds of acts of righteousness that bring the mercy of God Almighty to His servants and be a reason for the
... Show More