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In this study, the potential implementation of three different low-GWP refrigerants (R32, R452B, and R454B) as replacements for R410A was investigated. The study was performed using a simulation tool developed by the authors called RACHP-Lab, which is a vapor compression system simulation tool developed based on physicsbased simulation for typical mini-split air conditioners. The simulation study was carried out and validated using experimental performance data of 10 different air conditioning units available in the Egyptian market. The units included fixed-speed or variable-speed compressors and operated in cooling or heating modes. Drop-in replacement with the new refrigerants was carried out. For R32, the capacity increased between 4.9% and 13% for cooling cases, and 6.3% and 12.4% for heating cases. However, COP did not improve in all cases. For R452B and R454B with direct replacement, the capacity nearly remained the same, with an increase of COP between 1.6% and 8.0%. Soft optimization was also conducted on cooling cases where compressor suction superheat, condenser subcooling, and compressor volumetric speed were optimized to maximize COP while maintaining the original capacity of R410A. R32 showed an improvement of COP over R410A between 4.6% and 15.5%, while for R452B and R454B between 2.2% and 13.2%. [ABSTRACT FROM AUTHOR]

Developing countries, particularly those with high ambient temperatures (HAT), are experiencing a surge in air conditioner (AC) installations. Fixed-speed ACs, which rely on on–off control, are the most used. However, fixed-speed ACs lack humidity control and experience compressor cycling, leading to poor thermal comfort and increased energy consumption. Variable-speed compressor technology eliminates compressor cycling, which increases the effective coefficient of performance, especially at part-load conditions. This study compares the transient performance of variable-speed and fixed-speed AC units in Cairo, Egypt, as an example of a HAT environment. During a 2-month experimental investigation, the variable-speed unit provided 41% electrical energy savings while maintaining a comfortable environment. Analytical modeling using a machine learning model trained by the experimental measurements predicted annual energy savings of 473 kWh/year and an overall electrical energy savings percentage of 30.5%. The study also explored different scenarios for implementing variable-speed ACs in Egypt, a developing HAT country. With a 60% market penetration for variable-speed AC as the most probable scenario, the electrical energy savings up to the year 2032 add to 1.33 TWh, leading to 79.3 million USD in cost savings and 2.64 MMT of CO2 emissions reduction. [ABSTRACT FROM AUTHOR]

The goal of this study is to perform an analysis of the performance of radiant cooling panels using experimental testing and transient system simulation software. The effect of design parameters such as water supply temperature and water flow rate on thermal comfort and energy efficiency is studied. Two control schemes are used in the study in which either the water flow rate or the water temperature difference between the inlet and outlet of radiant panels is held constant. This paper demonstrates the modeling and validation of a radiant cooling system in TRNSYS and uses this model to study the performance of the system during the cooling season in Egypt. It was found that the lower water temperature of 16 °C was found to be suitable for achieving thermal comfort. The constant water flow rate control scheme showed a 5% less unmet hours percentage than the constant water temperature difference, but the latter used 38% less electrical energy. A constant water temperature difference control scheme can achieve better thermal comfort with an unmet hours percentage down to 12.5% by coupling the system with a dehumidification device. [ABSTRACT FROM AUTHOR]