Ejector expansion cycle; Exergy analysis; Separate Sensible and Latent Cooling
While the overall system efficiency of split air conditioning (AC) systems has improved over the last three decades, residential air handling units (AHUs) used in those systems have essentially stayed the same in size, shape, form, and efficiency. Incremental improvements have been made to AHUs to address safety, functionality, and energy-efficiency concerns, however, their overall structure has remained the same. A promising technology that addresses fundamental challenges with conventional cycle efficiencies are ejector-based cycles, more commonly employed in refrigeration applications, but with great potential in AC systems as well. An ejector employed as an expansion device can recover expansion losses, boost pressure, and facilitate a dual evaporator system. This paper presents four categories of ejector enhanced vapor compression cycles (VCCs) leading to seven potential system concepts: standard two-phase ejector, two variants of condenser outlet split (COS), diffuser outlet split (DOS), and three variants of separator outlet split (SOS). The concepts were investigated via numerical model studies and two promising ejector enhanced cycles for a residential AC application emerged: COS and DOS. The COS and DOS ejector enhanced cycles improved seasonal energy efficiency ratio (SEER) by 4%–8% above a 15 SEER baseline AC system and improved the total coefficient of performance (COP) by 9%–11%. With the COS or DOS ejector enhanced cycles, losses quantified by exergy destruction were reduced by up to 18%.