Experimental Performance Investigation of Domestic Refrigerator Charged by R600a and R134a

تمت دراسة اداء منظومة تبريد تعمل بانضغاط البخار (ثلاجة منزلية) شحنت بمائعي التبريد (R600a) و (R134a) دراسة عملية. وتم اقتراح مائع التبريد (R600a) كمائع بديل عن مائع التبريد التقليدي (R134a)، وكان التحقيق العملي لعدة عوامل تشغيلية مؤثرة للمنظومة مثل: التاثير التبريدي للمبخر (RE)ونسبة الانضغاط (Pr) وكمية الحرارة الملفوظة في المكثف (qcond) ودرجة حرارة المبخر المخصص للتجميد (FE) ودرجة حرارة المبخر الثانوي المخصص للتبريد (RE). وقد تبين من النتائج التي تم الحصول عليها ان استبدال (R134a) بـ (R600a) مقبول و منطقي خاصة بقارنة النتائج و السلوك المتشابة للمائعين بدراسة العوامل المشار اليها اعلاه .اعظم وادنى تفاوت في نسبة الانضغاط كان يتراوح بين (8%) الى (23%) على التوالي، بينما معامل اداء المنظومة (COP) للمائع (R600a) كان اقل من (COP) للمائع (R134a) بمقدار (12%) تقريبا وبالرغم من وجود أختلاف بين المائعين لكن يمكن اعتبار نتائج (R600a) مقبولة واعتباره بديلا ناجحا للمائع (R134) كون (ODP) له  تعادل صفرا و(GWP) قليلة جدا يمكن اهمالها وهذان المؤشران مهمين جدا للبيئة والحفاظ على معدل درجة الحرارة والمناخ . The performance of vapor compression refrigeration (domestic refrigerator) charged with (R600a) and (R134a) was experimentally studied. A new Alternative refrigerant(R600a) suggested  of the conventional (R134a).Various parameters were investigated such as refrigeration effect , pressure ratio , condenser heat rejection , evaporator capacity, RE and FE compartments temperatures .It is observed that replacing (R134a) with (R600a)  was acceptable value specially by comparing conditions closely results .The minimum and maximum deviation in pressure ratio was about (8% to 23%), respectively, and the COP of (R600a) was less than the COP of  (R134a) about (12%) .In spite of that, this reduction was considered acceptable due to ODP of (R600a) were zero and negligible by GWP.&nbsp

Comparison of Soot Particle Movement based on Crank Angle

In a diesel engine, soot was produced due to incomplete fuel combustion in a combustion chamber. Some of this soot sticks to the cylinder wall and interferes with lubricant oil. This soot causes the lubricant oil to contaminate and this increases its viscosity. Contamination of lubricant oil is one of the major causes of engine wear. Therefore, the focus of this study is on soot movement in diesel engine that is the initial step to avoid contamination of lubricant oil. This work uses the data of the formation of soot particles from Kiva-3 v obtained from previous investigation and then simulated it by a Matlab routine. Kiva-3 v produced velocity vectors of the soot, fuel, temperature, pressure and others. Matlab routine uses trilinear interpolation and fourth order Runge Kutta method in order to calculate soot movement in a combustion chamber. In addition, the influence of drag force is considered in the calculation to achieve a higher accuracy. The objective of this study is to compare soot particle movement between 8° ATDC and 18° ATDC. Results show that 8° ATDC has a high risk to contaminate lubrication oil in certain location compare to 18° ATDC

Analysis of Soot Particle Movement in Diesel Engine under the Influence of Drag Force

The formation of soot is influenced by the composition of air entrainment and structure of hydrocarbon in the fuel. Soot will then form during combustion in a diesel engine. Some of the soot particles will be released from the engine through the exhaust nozzle and some will stick to the cylinder walls. The soot that sticks to the cylinder wall can affect the lifetime of the lubricant oil. Subsequently this will decrease the durability of the diesel engine. By understanding the movement of the soot particles, the effect to the engine can be decreased. Therefore, the initial position and last position of soot particle was recognized through this study. The data for the formation of soot particles in the diesel engine was obtained from previous investigation. The study of soot movement at 8° crankshaft angle under the influence of drag force with different radial, axial and angular settings were carried out using a MATLAB routine. The results showed that the movement of soot particle will change with different parameter settings. Besides that, comparison of the results of soot particle movement influenced by drag force and without drag force has been carried out. It was observed that drag force caused shorter soot particle movement path and moves them away from the cylinder wall

The Effect of Spark Timing on the Spark Ignition

<p> In this work the effect of spark timing on the spark ignition engines is investigated by computer simulation and experimental test for speeds of (1500,2000,2500,3000 and 3500)rpm at spark timing of (20^o,30^o,40^o,50^o and 60^o) before TDC for each speed. This is done in order to find a suitable  mathematical expression for spark ignition advancing with respect to the speed of the engine to predict the correct ignition advance  as in real engines .The results showed that the method of using a mathematical expression is more realistic and reasonable  comparing  with the results obtained by other workers.</p><p> <strong></strong></p

Hybrid nanofluid to enhance heat transfer under turbulent flow in a flat tube

The heat transfer enhancement by utilizing hybrid nanofluid is a new class of heat transfer enhancement. In this paper, CFD model with commercial software adopting the finite volume method and SIMPLE algorithm has been conducted. Mixture of Aluminum Nitride (AlN) and alumina (Al2O3) nanoparticles into water as a base fluid is considered as a new concept of hybrid nanofluid for enhancing heat transfer. It was performed the simulation procedures with the volume fraction (1, 2, 3 and 4%) and Reynolds number are changing from 5000 to 17000. The heat flux applied along the elliptical tube is 7000 w/m2 and the nanoparticles size diameter is fixed at 35 nm. The validation of computational results has been performed with experimental data available in the literature. The results indicated that the hybrid nanoparticles of AlN - Al2O3 suspended in water as a base fluid tends to enhance heat transfer significantly. Keywords: Hybrid, Nanofluid, Performance, Turbulent, CFD, ANSY

Evaluation of Alton Kobry Region Ground Water for Civil Uses

This study has been performed at the Alton-Kobry region to indicate the   suitability of the ground water which is important source for domestic uses.      The samples taken from (19) wells at different locations and tested at laboratories of north gas company in Nov.-2010.The tests included (electrical conductivity, total dissolved solids, pH-value, concentration of some anions) were all conducted for each sample.    The results revealed that surveyed ground water were free from pollution and almost suitable for domestic use.        Some investigated parameters appeared to be near the recommended limits set by Iraqi standards, while others exceed the recommended values that the chemical treatments are necessary.</p

Multi-institutional retrospective analysis of adverse events following rigid tracheobronchoscopy.

Background and objective: Rigid tracheobronchoscopy (RTB) has seen an increasing interest over the last decades with the development of the field of IPM but no benchmark exists for complication rates in RTB. We aimed to establish benchmarks for complication rates in RTB. Methods: A multicentric retrospective analysis of RTB performed between 2009 and 2015 in eight participating centres was performed. Results: A total of 1546 RTB were performed over the study period. One hundred and thirty-one non-lethal complications occurred in 103 procedures (6.7%, 95% CI: 5.5–8.0%). The periprocedural mortality rate was 1.2% (95% CI: 0.6–1.8%). The 30-day mortality rate was 5.6% (95% CI: 4.5–6.8%). Complication rate increases further when procedures were performed in an emergency setting. Procedures in patients with MAO are associated with a higher 30-day mortality (8.1% vs 2.7%, P &lt; 0.01) and a different complication profile when compared to procedures performed for BAS. Conclusion: RTB is associated with a 6.7% non-lethal complication rate, a 1.2% periprocedural mortality rate and a 5.6% 30-day mortality in a large multicentre cohort of patients with benign and malignant airway disease. © 2020 Asian Pacific Society of Respirolog

A Pilot Study Comparing Aortic Valve Area Estimates Derived from Fick Cardiac Output with Estimates Based on Cheetah-NICOM Cardiac Output.

Contains fulltext : 221539.pdf (publisher's version ) (Open Access)Cardiac output during cardiac catheterization is often estimated using the modified Fick method (CO(Fick)). In this proof-of-concept, prospective non-randomized study carried out in a single academic healthcare centre, we examined whether replacing CO(Fick) in the Gorlin formula with Cheetah-NICOM monitor cardiac output (CO(Cheetah)) could produce an accurate and precise estimate of aortic valve area in patients with severe aortic stenosis. In twenty-six subjects, CO(Fick) and CO(Cheetah) were obtained concurrently. A spot and 3-minute running average of CO(Cheetah) was used. Bland and Altman analysis was used to derive bias, 95% limits of agreement (LOA) and confidence intervals (CI). The mean difference (bias) between AVA(Cheetah) (average) and AVA(Fick) was 0.11 cm(2) and the 95% LOA were ±0.42 cm(2). The 95% CI of the bias was 0.02-0.2 cm(2). The bias and 95% LOA of AVA(Cheetah) (spot value) were 0.14 ± 0.42cm(2), with a 95% CI of 0.06-0.23 cm(2). No proportional bias was present. AVA(Cheetah) thus appears to be a reasonably accurate measure of AVA in patients with severe aortic stenosis compared to AVA(Fick) measured using a modified Fick CO. However, the limits of agreement were not narrow enough to consider AVA(Cheetah) and AVA(Fick) interchangeable