Using Natural Refrigerants Propane (R290) & Carbon Dioxide (R744) as Direct & or Indirect Heat Pump Systems to Address PFAS Issue

<div class="section abstract"><div class="htmlview paragraph">Per - and polyfluoroalkyl substances – known as PFAS are man-made chemicals that do not occur naturally. PFAS are widely used, long lasting chemicals, components of which break down very slowly over time. Scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals. Because of their widespread use and their persistence in the environment, many PFAS are found in human and animals’ blood all over the world and are present at low levels in a variety of food products and in the environment. PFAS are found in water, air, fish, and soil at locations across the nation and the globe.</div><div class="htmlview paragraph">Both refrigerants (HFC-134a & HFO-1234yf) that are currently used in mobile air conditioning systems (MACS) create PFAS. Hence, various countries are looking into banning chemicals that create PFAS. Natural refrigerants are being proposed as alternative refrigerants as they do not create PFAS. Hence, Propane (R290) and Carbon-Dioxide (R744) are being considered as alternate refrigerants for mobile HVAC systems for internal combustion engine (ICE) vehicles and for electric vehicles (EVs). However, propane is highly flammable, and carbon-dioxide operates at extremely high pressures that needs to be addressed.</div><div class="htmlview paragraph">In this paper, the author has presented the following details: (i) Current situation of PFAS that the world is facing by providing details of actions by European countries, US and Japan. (ii) Details of the alternate refrigerants including thermodynamic and thermophysical properties comparison that affects heat transfer coefficients and pressure gradients during single and two-phase fluid flow. (iii) Safety Considerations. (iv) Details of the test that the author has conducted with hydrocarbon refrigerants and with carbon-dioxide. (v) Finally, the details with heat pump system architectures are presented using natural refrigerants as direct expansion and indirect systems from a safety and performance perspective for ICE and EVs. It should be noted that currently many OEMs and suppliers have heat pumps systems with high degree of complexity and there is no common standard architecture for the ICE/EV heat pumps system.</div></div>