In the present work, the effects of different operating parameters on the performance of a gravity-assisted heat pipe-based indirect evaporative cooler (GAHP-based IEC) were investigated. The aim of the theoretical study is to evaluate accurately the cooling performance indicators, such as the coefficient of performance (COP), wet bulb effectiveness, and cooling capacity. To predict the effectiveness of the air cooler under a variety of conditions, the comprehensive calculation method was adopted. A mathematical model was developed to simulate numerically the heat and mass transfer processes. The mathematical model was validated adequately using experimental data from the literature. Based on the conducted numerical simulations, the most favorable ranges of operating conditions for the GAHP-based IEC were established. Moreover, the conducted studies could contribute to the further development of novel evaporative cooling systems employing gravity-assisted heat pipes as efficient equipment for transferring heat.

A hybrid air conditioning system, which is composed of a novel gravity-assisted heat pipe (GAHP)-based indirect evaporative cooler (IEC) and direct expansion (DX) cooling coil, is proposed and investigated here. After developing a mathematical model to describe the performance of the GAHP-based IEC, the hybrid system is evaluated during the cooling design day for providing thermal comfort for an office building in Poland. The results are obtained and compared with the combination of a rotary heat exchanger (RHE) and DX cooling coil as the conventional hybrid system. The comparison is performed by analyzing cooling capacity, electricity consumption, and coefficient of performance profiles, which describe the technical, energy, and efficiency aspects, respectively. The results show that the GAHP-based IEC hybrid system is able to enhance the energy performance significantly compared to the conventional one. The proposed hybrid HVAC system improves COP by 39.2% and reduces electricity consumption by 45.0%, according to the design-day of 24 August and the outdoor temperature of 30 °C. As a result, the total operating cost for the assumed cooling season is reduced by 51.7%.

Since the fossil reserves are depleting day by day, the trend of modern energy sector is going towards renewable energy. The demand of solar power plants is therefore at the peak nowadays across the globe. However, the construction of these plants is extremely dependent on feasibility study to estimate the real solar potential before installing it in any region. To evaluate the solar energy potential of Peshawar region in Pakistan, Ground-based global horizontal irradiance (GHI) and direct normal irradiance (DNI) were compared with satellite-based model SUNY. Ground measurements were done at the University of Engineering and Technology Peshawar (UET Peshawar) with the help of pyranometer and shadowband irradiometer. Comparison of the data showed that there was a maximum difference of 42.90% in ground and satellite-based GHI in the month of December. Minimum difference in GHI was found for the month of March that was −3.83%. Moreover, ground-based GHI was overestimated in the month of February, March, and April, while in rest of the months, satellite values of GHI exceeded the ground measurements. Similarly, maximum difference of 55.86% was found in the month of November between ground and satellite-based DNI while minimum difference of −3.34% was seen in DNI in the month of March between the two data. Furthermore, satellite-based DNI was underestimated in the months of February, March, and April while in rest of the months it was overestimated compared to ground measurements. In addition to this, correlation of ground and satellite-based GHI and DNI showed R² value of 0.8852 and 0.4139, respectively. The results of this study revealed that the difference between ground measurements and satellite values was considerable and hence real time measurements are necessary to properly estimate solar energy resource in the country.

Evaporative cooling is a sustainable and energy-efficient technology based on water evaporation to achieve cooling. It uses air (R-729) and water (R-718) as refrigerants, so its effect on global warming is limited. Recent research focuses development of porous heat exchanger surfaces to be used in evaporative cooling technology with intermittent water spray. However, non-porous surfaces were not investigated. Here, we present the possibility of implementing intermittent water spray in a non-porous indirect evaporative cooler. The experimental results show that it increases the cooling capacity when compared to the constant water spray for chosen outdoor air parameters (20–30 °C and 40–50% relative humidity). Also, the time after the outlet air temperature achieves minimum value (4–6 min) is presented for a certain non-porous heat exchanger. The maximum cooling capacity obtained without spraying is 25–64% higher than the cooling capacity in steady-state conditions under constant water spraying. The regression model approach is employed to describe the observation. The results introduce a new path in evaporative cooling technology development. They also create the possibility of improving the effectiveness of existing systems by modifying only the water system management, without any changes in construction or replacing the heat exchanger.

Dewpoint indirect evaporative cooling (DIEC) offers an energy-efficient, eco-friendly alternative to conventional air conditioning by using water and air to lower temperatures. With the rising demand for sustainable cooling solutions—especially in regions facing water scarcity and high energy costs—optimizing these systems for real-world conditions is more important than ever. One major challenge is ensuring that DIEC systems perform well when water is supplied intermittently rather than continuously. In this review, we examine how intermittent water supply affects the cooling performance and overall efficiency of DIEC systems. We discuss recent studies that highlight the importance of key factors such as the properties of heat exchanger materials, design modifications, and control strategies. Our analysis reveals that while innovative materials like hydrophilic membranes and adaptive design features can improve performance, their widespread use is often limited by cost and scalability. We also point out critical research gaps, particularly in applying intermittent water spraying to non-porous heat exchangers. Overall, our findings underscore the need for integrated water management strategies in DIEC design. We advocate a cross-disciplinary approach—bridging fluid dynamics, material science, and environmental engineering—to develop more resilient and sustainable cooling technologies.

Heat transfer is present in all modern engineering applications and plays a fundamental role in improving the efficiency of energy conversion systems