Experimental Investigation of Gas-Bubble Formation due to Supersaturation in a Plate Heat Exchanger

Enhancing the efficiency of current energy-consuming systems is crucial to mitigating global warming. Heating systems contribute substantially to global carbon emissions and energy consumption. Therefore, examining their performance is vital for the Green Transition. The presence of air in heating systems’ liquid circuits is one key uncertainty affecting their performance. Air can enter a heating system through component leaks or as dissolved gas in feed water, the latter potentially emerging as bubbles due to local supersaturation. This study experimentally investigates the impact of bubble formation from water supersaturation in a plate heat exchanger (PHE). Cold streams are studied in a single-channel PHE for Reynolds numbers ranging from 538 to 2010, with an inlet temperature of 30°C. The saturation level is adjusted between 15% and 100%. Monitoring PHE’s outflow reveals the emergence of bubbles at all Reynolds numbers when the liquid is saturated. Reducing Reynolds number results in a growing coverage of PHE’s surface area with air bubbles, along with increasing their diameters, which translates into a decrease in heat transfer. A comparison of the overall heat-transfer coefficient between low and high saturation levels reveals an enhancement ranging from 0.6% to 3%, with a maximum uncertainty of ±0.3%.