Performance assessment of an organic Rankine–Vapor compression cycle (ORC-VCR) for Low-Grade compression heat recovery

Power consumption of the compression process in air separation units can be significantly reduced by precooling the inlet air of the air compressors with an organic Rankine cycle and vapor compression cycle (ORC-VCR). To date, most of existing researches on compression heat recovery focus on thermodynamic modelling and performance analysis. This paper presents an experimental assessment of a compression heat recovery system based on a mechanically coupled ORC-VCR for air separation units. Experimental investigations on the stabilities of gas bearing fluid supply system and motor cooling system were conducted. Results indicate that both are capable of maintaining stable operations while achieving the designed functions. System performance tests were performed with various mass flow rates, pressure ratios of high-temperature and low-temperature evaporating pressure. The increase in the ratio of two evaporating pressures leads to a dramatic decrease in the system coefficient of performance (COP). A COP of 0.63, a cooling capacity of 14.2 kW at a refrigeration temperature of 14.6 °C were achieved at a rotation speed of 25822 rpm with full-load operation. This work experimentally demonstrates an effective compression heat recovery system based on ORC-VCR, which suggests the potential application of the compression heat recovery system in air separation units.