Research Projects

Typically, human comfort requires a 24-26 °C temperature, 40-60% relative humidity, along with 99.9% clean and pure air. Therefore, a good air conditioner must provide all these air parameters with less power consumption and high cooling performance. In the market, air conditioners (split ACs with 1-3 TR capacity) are available that are not provided with good ventilation and circulate the same trapped room air in the evaporator, which results in the accumulation of CO₂ and microorganisms that emerge from human breathing inside the room. In the present work, a room air conditioning system of 1 TR cooling capacity with propane (R290) refrigerant, a dehumidification bed operated with waste heat from the compressor, a proper ventilation arrangement (recirculation duct), and the use of a liquid line suction line heat exchanger (LLSL-HX) in a simple VCR system are planned to be developed to increase the performance (reduction in power consumption) along with the supply of hygienic air for human comfort. Propane is an alternative for a low-GWP, low-boiling-point, and non-toxic refrigerant for a room AC system. Propane has several advantages as a refrigerant, namely, lower compressor discharge temperature, lower volumetric flow compared to R12 and R134a, suitability of mineral oils, polyolesters, and PAGs as compressor lubricants, zero ODP, near-zero GWP (3), easy availability, cost-effectiveness, good COP or energy efficiency, no temperature glide (i.e., not a mixture but a pure component), and excellent thermodynamic and transport properties. Propane (R290) is classified as a safety group A3 refrigerant (highly flammable), with its flash point and auto-ignition temperatures being 104 °C and 470 °C, respectively. The lower and upper flammability limits of R290 are approximately 2% and 10%. Earlier research indicated 150 g as the charge limitation for flammable refrigerants in refrigeration systems. However, regulation IEC 60417-6415 has raised the charge limit to 500 g, which means propane can be used even in moderately big systems. Fire hazards can be minimized by following the charge limitations and by providing sufficient room space, ventilation, and safety measures. The liquid line suction line heat exchanger is the intermediate heat exchanger that can precool the refrigerant before expansion in the TXV by absorbing the heat from the refrigerant after condensation in the condenser to the cold refrigerant before entering the compressor. In the present work, the system will be provided with a recirculation fresh air duct, which can provide pure and clean air for the evaporator for cooling to a comfortable temperature. The airflow control valves are fitted inside this recirculation duct, which can control the amount of fresh air and recirculation air in the cabinet. Compressor heat can be utilized in the dehumidification bed, which reduces the latent heat load of air moisture on the evaporator, which increases the power savings of the compressor.