Research on heat transfer characteristics of serpentine tube

Abstract

In order to reduce energy consumption and improve the efficiency of CO2 heat pumps, a numerical simulation method was used to study the heat transfer characteristics of supercritical CO2 in serpentine tube air cooler based on Fluent software. The flow characteristics of supercritical CO2 in a serpentine tube were mainly investigated. The heat transfer performance of the serpentine tube was analyzed by changing the operating pressure, the mass flow rate of CO2, and cooling water. The results show that the periodic reversal of centrifugal force in a serpentine tube will cause the temperature and velocity gradients to exhibit a periodic trend of internal and external interdiffusion; The closer the supercritical CO2 pressure is to the critical point, the higher the average heat transfer coefficient is. The average heat transfer coefficient at a pressure of 8 MPa is 24.37% and 42.53% higher than that at 9 MPa and 10 MPa, respectively. The average heat transfer coefficient of supercritical CO2 will increase with the increase of the CO2 mass flow rate, and decrease with the increase of the cooling water mass flow rate. The increase of the cooling water mass flow rate will not have an impact on the heat transfer coefficient of the peak point, but will advance the location of the peak point. The research results provide a theoretical basis for the design, operation and thermal efficiency improvement of the serpentine tube air cooler of supercritical CO2 heat pump, and have important guiding significance for the application of high efficiency heat exchangers.

Keywords

• engineering thermodynamics; supercritical carbon dioxide; numerical simulation; heat pump; serpentine tube