Thermal comfort in the vehicle cabin environment is an important factor for passengers of both internal combustion engines and electric vehicles. Heating, Ventilation and Air Conditioning (HVAC) is a critical system for electric vehicles (EVs) as it is the second most power consumer after electric motor. Novel solutions dedicated to EV, including thermoelectric air conditioning (AC) modules, vapor compression refrigeration (VCR), cycle positive temperature coefficient (PTC) heater as well as heat pumps (HP), are being investigated to maintain a stable and comfortable interior environment under hot and cold weather conditions. At present, the mostly dominated automotive AC systems are those using R134a refrigerant characterized by high global warming potential.
Therefore, an innovative and ecofriendly AC system design still must be developed to supply sufficient cooling or heating capacity while minimizing the influence of the AC system on driving ranges and environmental performance.
A potential solution is represented by vortex tube-based AC systems. The vortex tube is a fluid dynamic device which is capable to separate an inlet compressed flow in two streams at hot and cold temperature, respectively.
The objective of this study is to investigate the feasibility of the use of vortex tube integrated to the transcritical R744 (t-R744) AC system for an electric vehicle. Using a preliminary configuration of a vortex tube device developed for a commercially available mini-EV, the energy analysis of the system under various experimental conditions was performed and its performance parameters under steady state operation were evaluated.
Specifically, the Coefficient Of Performance (COP) of the vortex tube transcritical R744 AC system and its influence on the driving range were assessed for different external weather conditions. Finally, this solution is compared with the basic transcritical R744 cycle and with its mostly used modification which considers an internal heat exchanger for the same working conditions of VCR.