As automotive power-train systems become more efficient, less waste heat is available for vehicle passenger cabin warming. As a result, alternative heating technologies are being investigated to alleviate this shortcoming. One alternative is to operate the existing A/C system in reverse (heat pump mode), thus providing supplemental heat.
Recently, the environmental impact of refrigerant emissions has come under global scrutiny. The concern is their potential for global warming. Thus, the environmental characteristic of merit that makes for a more benign refrigerant in terms of emissions is lower Global Warming Potential (GWP). R-152a is a more environmentally benign refrigerant compared to R-134a with a GWP of 120 vs. 1,300 [1] and [2]. Both refrigerants are hydro-fluorocarbons - HFCs - (contain no chlorine) and hence, have zero ozone depletion potential.
An environmentally benign refrigerant touted as a potential replacement for R-134a, is CO2. Analysis and experimental work [3, 4] indicate great potential for trans-critical CO2 systems operating in heat pump mode. The study of R-152a and R-134a heat pumps in this paper demonstrated similar results.
This paper quantifies the heat pump capacity of R-152a and compares it to that of R-134a using engine coolant as a heat source. An actual production vehicle modified to have a heat pump system was used to demonstrate the performance in a climatic automotive wind tunnel.