In this paper, a first- and second-law analysis of vapor compression refrigeration is presented to estimate and propose the replacement of R134 with working fluids having less global warming potential (GWP) and less exergy destruction and irreversibilities. Six different refrigerants were studied, namely, R717, R1234yf, R290, R134a, R600a, and R152a. A thermodynamic model was designed on Engineering Equation Solver (EES) software, and performance parameters were calculated. The model was deployed on all six refrigerants, while the used output parameters of performance were cooling capacity, coefficient of performance, discharge temperature, total exergy destruction, relative exergy destruction rates of different components, second-law efficiency, and efficiency defect of each component. The performance parameters were estimated at different speeds of the compressor (1000, 2000, and 3000 rpm) and fixed condenser and evaporator temperatures of 50 °C and 5 °C, respectively. The isentropic efficiency of the compressor was the same as the volumetric efficiency, and it was taken as 75%, 65%, and 55% at the compressor speeds of 1000 rpm, 2000 rpm, and 3000 rpm, respectively. A comparison of the performance parameters was presented by importing the results in MATLAB. It was found that the compressor had the highest exergy destruction compared to the other components. It was found that R152 was the refrigerant with zero ozone depletion potential (ODP) and a GWP value of 140 with less exergy destruction and irreversibilities. Moreover, it was easy to use R152a with good thermodynamic characteristics. It is estimated that R152a is a suitable replacement for R134a, as it can be used with few modifications.

Road transportation has received the attention of researchers due to its higher carbon footprint. Alternative fuels present major advantages in terms of environmental sustainability. For this reason, an enviro-economic analysis of alternative fuels carries great significance. However, scarce attempts have been rendered in order to ascertain the impact of a hydroxy gas (HHO) and compressed natural gas (CNG) mixture on sustainable environmental development. The current study addresses this issue by employing an HHO–CNG mixture and gasoline in spark ignition (SI) engines for the purposes of performance and environmental pollutants measurement. Then, engine emission data were substituted for Weibull distribution in order to establish suitability for 50 and 95% confidence intervals (CIs). The mixture outperformed gasoline in terms of brake-specific fuel consumption (BSFC) and emission contents. On average, hydroxy gas with CNG produced 10.59% lower oxides of nitrogen (NO_X) comparative to gasoline. Finally, the enviro-economic analysis also turned out to be in favor of the hydroxy gas mixture owing to a saving of 36.14% in USD/year due to 27.87% lower production of carbon dioxide (CO₂) emission.

Growing environmental concerns over global warming and depleting fossil fuel reserves are compelling researchers to investigate green fuels such as alcoholic fuels that not only show the concrete decrement in emissions but also enhance engine performance. The current study emphasizes the influence of different alcoholic fuel blends in gasoline on engine performance and emissions for an engine speed ranging from 1200 to 4400 rpm. The obtained performance results demonstrate that the brake power and brake thermal efficiency (BTE) increased with an incrementing blend percentage of ethanol and methanol in gasoline (EM). The minimum brake specific fuel consumption (BSFC) was ascertained using pure gasoline followed by E2 and then E5M5. The NO_x and CO₂ emissions can be described in the decreasing order of E, EM and gasoline due to same trend of exhaust gas temperature (EGT). CO results were in reverse order of CO₂. HC emissions were found in the increasing order of E, EM and pure gasoline. E10 performed better among all blends in terms of less exhaust emissions and engine performance. However, EM blended with gasoline significantly reduced NO_x. E5M5 produced 1.9% lower NO_x emission compared to E10 owing to 1.2% lower EGT. Moreover, greenhouse gases such as CO₂, which is mainly responsible for global warming reducing by 1.1% in case E5M5 as compared to E10.