Experimental investigation of the thermal performance in a single-component two-phase flow in multistream multi-fluid plate-fin heat exchangers

Abstract

This paper focuses on evaluating the effects of flow rate and temperature changes of hot and cold fluid flows in multistream multi-fluid plate-fin heat exchangers with a single-component two-phase flow in the middle heat exchanger. This three-fluid heat exchanger included three layers with offset strip and wavy fin configurations. In the adjacent heat exchanger with offset strip fins, hot and cold fluids were flowing, while the middle heat exchanger with wavy fins contained a single-component two-phase flow (condensed vapor). The Nusselt number, friction factor, the thermal performance factor, and the heat transfer surface contribution of the middle heat exchanger with each of the adjacent heat exchangers, were obtained using the measured experimental data. The results indicate that the two-phase Reynolds number was between 500 and 1800, and the vapor quality varied in the range of 0.17–0.56. Also, the heat transfer surface contribution of the adjacent cold and hot fluids was between 0.18 and 0.5. The two-phase flow in the wavy channel has a wavy and stratified pattern. The examinations showed that raising the Reynolds number of hot and cold fluids, respectively, led to maximum 13.8 % and 9.5 % of reduction in the vapor quality, 8.8 % and 9 % of increase in the two-phase Nusselt number, and 18 % and 12 % of reduction in the average value of friction factor. The domain change in the two-phase vapor quality, the two-phase fluid heat transfer surface contribution, and the flow pattern determination parameters including the dimensionless mass parameter and the Lockhart-Martinelli parameter was 33.67 %, 80.81 %, 32.72 %, and 19.09 %, respectively. As the Reynolds number of the cold fluid was changed, the variation domain of these parameters was higher compared to when the Reynolds number of the hot fluid was altered. Increasing the dimensionless temperature of the hot and cold raised the vapor quality by 12–16 %. The experimental results revealed that by decreasing the temperature of adjacent fluids and increasing their Reynolds number, the thermal performance factor of the two-phase flow was increased.