Experimental Investigation with R1234yf Condenser Airflow Blockages of Non-Hotspot and Hotspot Objects to Impact on A/C System Performance 2016-01-0255

This paper addresses R1234yf A/C system performance impacted by condenser airflow passage blockages of nonhotspot and hotspot objects. With the modern vehicle design trend, more and more chances exist in blocking condenser airflow passages by objects such as TOC (transmission oil cooler) or fine grills etc. These objects create hotspots and narrowed airflow passages to the condenser and result in A/C performance degradation. It is important to understand the specific area of the condenser which is most impacted by a blockage so this area can be avoided in the design/packaging of front end components. In addition, it is important to understand the magnitude of performance loss associated with the specific areas of blockage. As a result of this understanding, optimal design locations for these blockages (including hotspots and grilles) can be proposed in order to mitigate the impact on A/C cooling performance.

The study indicated that blocking condenser airflow passages by both the hotspot and non-hotspot objects results in A/C performance degradation, i.e. increasing evaporator discharge air temperature and raising up compressor discharge pressure and temperature. With non-hotspot object blocking, the A/C performance with idle conditions has less impact than that with driving conditions. No significant difference for A/C performance impact between vertical and horizontal blockage was found. Hotspot object blockage located at the bottom of the condenser shows worse A/C performance than blockage located at the top of the condenser. A/C performance further degrades as the hotspot object temperature increases.

From the study, it is concluded that in order to minimize A/C performance impact from condenser airflow passage blockages, the blocking object located at the top of the condenser is the better choice than that at the bottom of the condenser, assuming the blockage is unavoidable altogether. Thus, the larger grille opening should be reserved for the bottom of the condenser, and any hotspots should be at a low temperature if possible.