In Pakistan, the utilization of renewable energy sources is increasing in order to reduce the electricity supply and demand gap. However, concentrated solar power (CSP) generation has not been considered in the country even though it has gained considerable attention worldwide. This study, as such, investigates the potential, performance, and economic analyses of four CSP technologies for different locations in Pakistan. Initially, an assessment of CSP sites, including solar resource, land, and water availability, was undertaken. Then, performance simulations of CSP technologies for four different locations of Pakistan, namely Quetta, Hyderabad, Multan, and Peshawar, were examined. For all cases, highest energy production was achieved in summers and lowest in winters, and CSP plants with evaporative cooling were found to be efficient compared to air cooling. The results also revealed that the Quetta and Hyderabad regions were promising for CSP development while parabolic tough (PT) and solar power tower (SPT) were the suitable CSP technologies for these regions. Specifically, the SPT plant with air cooling could be a favorable option for energy production in Quetta. Lastly, economic analyses revealed the financial feasibility of CSP plants in Pakistan since the levelized cost of energy is found to be significantly low.

This review presents the nucleate/convective boiling performance for a variety of important low global warming potential (LGWP) alternatives to commonly used high-global warming potential (GWP) refrigerants (such as R-134a, R404A, and R-410A, etc.). Efforts are stressed on the assessment of their evaporation pressure drop and heat transfer coefficient (HTC) characteristics. These alternatives include R-1234ze(Z), R-1234ze(E), R-1233zd (E), R-1234ze(E), R-410A, R-1234yf, and R-513A. The authors investigated the thermo-fluid properties within and outside a tube, mini-channel, micro-fin tube, and plate heat exchanger. The investigation of the numerical, experimental, and simulated results revealed that the evaporation pressure drop and HTC characteristics were dependent on a variety of variables. These factors include the working fluid’s thermodynamics and transport properties, the refrigerant’s mass flux, heat flux, saturation temperature, the vapor quality, the conditions and flow patterns, the orientation of the heating surface, and the geometry (shape, size, and surface area smooth/enhanced) of the heating surface. An expanded LGWP refrigerants, surfaces, and conditions database is needed. Mechanistic models may assist. These models can optimize boiling, anticipate heat transfer, and develop high-performance geometries.

The present investigation conducts a comparative analysis of the nucleate pool boiling heat transfer performance of two dielectric fluids, a low-GWP hydrofluoroolefin-based fluid (commercially known as Opteon™ SF33, referred to hereafter as SF33) and a perfluoropolyether-based fluid with a high GWP (commercially known as Galden^R HT55, referred to hereafter as HT55) under atmospheric pressure conditions. Pool boiling experiments and visual observations were performed to assess essential performance parameters, such as critical heat flux, heat transfer coefficient, and boiling dynamics. SF33 exhibits enhanced heat transfer performance, achieving markedly higher heat transfer coefficient values at all the heat flux levels and attaining superior critical heat flux relative to HT55. The results show that SF33 provides a consistently higher heat transfer coefficient, reaching approximately 12 W/m²·K at maximum heat flux, compared to only 6 W/m²·K for HT55, representing nearly a 100% improvement. The visual observations indicated that reduced surface tension and increased latent heat of vaporization of SF33 facilitate more frequent bubble nucleation and smaller bubble departure, thereby enhancing its boiling performance. Properties of SF33 render it a superior candidate for high-performance cooling systems in data centers and power electronics. The study concludes that SF33 is a more efficient and adaptable fluid for next-generation cooling systems, providing superior heat dissipation and energy efficiency relative to HT55.