Vol 14 Issue 1 April 2026-September 2026

Abstract: The air-conditioning (AC) system of a modern passenger car is a thermodynamically demanding subsystem that consumes 5–20 % of the vehicle's total energy under typical operating conditions. The choice of refrigerant directly determines the system's cooling performance, energy efficiency, and environmental impact. This paper examines the engineering implications of replacing R-134a, the dominant car AC refrigerant from the early 1990s through the mid-2010s, with R-1234yf, the hydrofluoroolefin (HFO) now mandated by international regulations on low global-warming-potential (GWP) refrigerants. The paper describes the architecture and operation of a typical car AC system, formulates the governing thermodynamic equations of the vapor-compression cycle, and synthesizes peer-reviewed experimental data. Drop-in substitution of R-1234yf for R-134a in unmodified car AC hardware reduces cooling capacity by 4–9 %, lowers the coefficient of performance (COP) by 3–7 %, increases refrigerant mass-flow rate by 10–14 %, and lowers compressor discharge temperature by 7–12 K, with the penalty growing at high ambient temperatures. Component-level optimization—particularly the addition of an internal heat exchanger and increased subcooling—can recover most of the lost performance. The paper concludes with a discussion of trifluoroacetic acid (TFA) atmospheric breakdown, proposed PFAS restrictions, and the role of integrated heat-pump systems in electric vehicles.

Keywords: car air conditioning, automotive HVAC, R-1234yf, R-134a, HFO refrigerant, vapor-compression cycle, coefficient of performance, electric-vehicle thermal management.

Title: Refrigerant Performance in Passenger-Car Air-Conditioning Systems: A Comparative Analysis of R-1234yf and R-134a

Author: Mr. Said Abdelaal Saleh Khattab, Eng. Ali Mejbel Aljadei

International Journal of Mechanical and Industrial Technology      

ISSN 2348-7593 (Online)

Vol. 14, Issue 1, April 2026 - September 2026

Page No: 29-37

Research Publish Journals

Website: www.researchpublish.com

Published Date: 07-May-2026

Abstract: This report aims to optimize the typical flat plate solar collector for the domestic solar heating system, considering improving solar collector efficiency and the useful solar energy gain enhancement. Consequently, piping costs and pumping power will be reduced compared to the conventional flat plate solar collector to get a compact and lightweight structure. They considered the flow distribution, which is crucial to enhancing the solar collector efficiency. Numerical studies were performed at two serpentine tube solar collector diameters (8 mm and 6 mm); both are identical in wall thickness, number of tubes, number of bends, the distance between tubes, and tube length. Several tube lengths are applied to each diameter to optimise, design, and evaluate the performance of both the serpentine tube collector energy gain and the economic benefits. Thermodynamic and heat transfer improvements are considered in this study applied to both models. Where the Reynolds number and the Dean number are significantly higher for the 6 mm tube, about five times, in contrast to the 8 mm tube. The serpentine tube length to diameter ratio (L/d) for the 6 mm diameter tube is 33 % higher than that for the 8 mm diameter tube, which reveals the thermodynamic and heat transfer performance enhancement of the collector tubes. Tube diameter variations have no significant influence on fin efficiency (absorber plate), but it has a considerable influence on the breadth reduction, which ranges between 91 % to 98 %. The tube collector efficiency of the 6 mm tube ranges among 78% to 94% in contrast to the 8 mm tube, which drops to 74% to 89%. Moreover, the heat removal factor F_R of the serpentine tube collectors' 6 mm and 8 mm is 98% and 91%, respectively. The fluid pressure drops in the serpentine tube collector correspond to tube diameter and length, while the pressure drop of the 8 mm tube ranges between 55 % to 80 % of the 6 mm tube for all tube lengths investigated. The annual collector heat gain of the 6 mm serpentine tube collector is 3982.5 W, which is approximately 25 % higher than that of the 8 mm serpentine tube collector. The financial analysis of the 6 mm serpentine tube collector shows a reduction of 22 % when compared to the 8 mm serpentine tube collector. The Propylenglycol 38% water mixture was applied in this study as the working fluid in the serpentine tube collector to determine the optimal operation performance of all samples stated earlier. In the particular studied case, the absorber plate width is considered to prove its influence on the collector performance. Moreover, fluid pressure drop, Reynold Number, and Dean Number in the collector tube.

Keywords: flat plate solar collector, domestic solar heating system.

Title: FLAT PLATE SOLAR COLLECTOR OPTIMIZATION USING DESIGN OF EXPERIMENTS APPROACH

Author: ENG - MUATH ALNUAIMI, ENG - BADER ALFADLY

International Journal of Mechanical and Industrial Technology      

ISSN 2348-7593 (Online)

Vol. 14, Issue 1, April 2026 - September 2026

Page No: 10-28

Research Publish Journals

Website: www.researchpublish.com

Published Date: 21-April-2026

Abstract: Aerodynamic optimization of sports car exterior structures has become a critical engineering discipline in the contemporary automotive industry, directly influencing vehicle performance, fuel efficiency, stability, and safety. This paper presents a comprehensive technical analysis of the aerodynamic principles governing sports car body design, examining both passive and active aerodynamic systems employed by leading manufacturers in the 2022–2026 model year range. The study synthesizes computational fluid dynamics (CFD) methodologies, wind tunnel experimental data, and real-world performance metrics from Ferrari, Porsche, Chevrolet, McLaren, and Lamborghini to evaluate aerodynamic efficiency through key parameters including drag coefficient (Cd), lift coefficient (Cl), and downforce generation. Mathematical formulations governing fluid behavior—particularly the Navier–Stokes equations, Bernoulli's principle, and boundary layer theory—are presented alongside practical applications in diffuser design, front splitter geometry, rear spoiler configuration, and underbody aerodynamics. Results indicate that advanced active aerodynamic systems can achieve drag coefficients as low as 0.25 Cd while simultaneously generating over 1,000 kg of downforce at speeds exceeding 250 km/h. The paper further examines regulatory frameworks imposed by the Fédération Internationale de l'Automobile (FIA) and Society of Automotive Engineers (SAE) standards. Future directions include machine learning-augmented CFD, biomorphic surface design, and adaptive materials for real-time aerodynamic adjustment.

Keywords: aerodynamics, sports car design, drag coefficient, downforce, CFD simulation, active aerodynamics, boundary layer.

Title: Aerodynamic Analysis of the Exterior Structures of Sports Cars

Author: Eng. Ali Mejbel Abdullah Aljadei

International Journal of Mechanical and Industrial Technology      

ISSN 2348-7593 (Online)

Vol. 14, Issue 1, April 2026 - September 2026

Page No: 1-9

Research Publish Journals

Website: www.researchpublish.com

Published Date: 20-April-2026