Improved inverse Joule Brayton air cycle using turbocharger units

Inverse Joule Brayton air cycle had been already implemented and tested for refrigeration purposes. In the open cycles described in the available literature, the operating fluid (air) is firstly compressed by a bootstrap (volumetric) compressor and then processed by a second (centrifugal) compressor and cooled; then, it is expanded in a turbine which drives the centrifugal compressor and discharges a cold flow which can be used (directly or indirectly) for refrigeration purposes. In this work, an inverse Joule Brayton air cycle has been studied with the employment of turbocharger units. Experimental tests have been performed in order to reproduce the state-of-the-art with a small automotive turbocharger unit. Measurements show Coefficient Of Performance (COP) smaller than unit together with minimum turbine exit temperature equal to -10°C. This is due to low components efficiency: the analysis of turbine and turbocompressor maps highlights a non-optimal coupling between them. Secondly, basing on these considerations, a new air cycle layout is proposed and analyzed. Calculations performed by means of a thermodynamic model show that higher COP and lower cycle minimum temperature can be achieved with this new cycle by means of better turbine and turbocompressor matching and bigger turbocharger units with higher components efficiency.