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HC-290 is a promising alternative for HCFC-22, which is an ozone depleting substance under Montreal Protocol. However, HC-290 charge is to be reduced because of its flammability. The objective of this study was to reduce the charge quantity of HC-290 in a split air conditioner, which was originally designed for HCFC-22. The effect of charge reduction on the performance of the HC-290 split air-conditioning system was studied experimentally by varying condenser tube diameter, length of capillary tube, and condenser air face velocity. Initially, simulation study was conducted using ART simulation software. In accordance with the simulation results, a 5.25 kW split air conditioner was modified and experimentally tested with HC-290 in a psychrometric test facility under standard test conditions as per IS 1391 part 2. The condenser tube diameter was reduced from 12.7 mm to 6.35 mm, while the length of capillary tube was increased from 650 mm to 820 mm with enhanced condenser air face velocities. It was found that with 300 g of HC-290 charge, the performance parameters such as cooling capacity, power consumption, and coefficient of performance were better than the baseline test with HCFC-22 in all conditions tested. [ABSTRACT FROM AUTHOR]

The performance comparison of two automotive air conditioning systems was experimentally studied under two typical cabin conditions viz; 27°C dry bulb temperature / 40% relative humidity and 40°C dry bulb temperature /40% relative humidity in a bench test rig for different blower speeds of the evaporator. Two mobile air conditioning systems viz; enhanced system having minichannel evaporator with integrated receiver-dryer condenser, and baseline system having conventional serpentine evaporator with parallel flow condenser were considered for the study. The compressor was the same for both the systems. The charge quantity, compressor speed, condenser air flow rate were suitably modified to maintain similar suction / discharge pressures, suction super heat and sub-cooling at all test conditions. The percentage of condensate retention during the dehumidification for both the evaporators were also compared. The comparison indicates that the average coefficient of performance of the enhanced system is higher in both low and high cabin temperature condition by about 15% and 8% respectively. The percentage of condensate retention in the evaporator of the enhanced system is lesser in the range of about 17–31% as compared to the base line system evaporator. It is also expected that a specific design of compressor for the enhanced system can yield better performance at all conditions. [ABSTRACT FROM AUTHOR]

Abstract In this article, detailed work on the heat transfer and fluid flow behavior of carbon-based hybrid nanofluid (multi-walled carbon nanotubes + graphene nanoplatelets/H2O) was studied numerically. The carbon-based hybrid nanofluids have been prepared experimentally and their measured properties were used for this study. The numerical study was carried out by passing the nanofluids under laminar flow through the tube side of the microchannel heat sink (MCHS). A constant heat flux on the heat sink base was applied and a single-phase model approach was used for analyzing the heat transfer. The nanofluid volume concentration varied from 0.01% to 0.2%. The improvement in the heat transfer coefficient is observed to be a maximum of 73%, with a maximum of 18% pressure drop variation across the MCHS for 0.2 vol%. The pressure drop variation across the MCHS is minimal for all the considered volume fractions of the nanomaterials. The results confirmed that the hybrid nanofluid possesses a remarkable heat transfer characteristic for transporting heat effectively. [ABSTRACT FROM AUTHOR]