Numerical investigation on a low energyconsumption heating method for recirculating aquaponic systems Abstract   In a recirculating aquaponic system (RAS), the heating method based on an electric heater requires considerable amounts of electrical energy to maintain the water temperature for optimal warmwater fish growth conditions. Minimizing electrical energy consumption in the RAS is a great challenge. To solve this problem, a novel heating method that uses a combination of helically coiled heat exchangers (HCHEs) and a thermal energy storage (TES) unit is proposed to replace the electric heater. Several studies on heating and cooling systems with HCHEs and TES tanks have been conducted, but their integration in RASs is very rare. In this study, the thermal energy of the water in an RAS was the research objective. A computational fluid dynamics approach was adopted for transient analysis and inspection of the HCHE model considering eight cases with four temperature levels, 55, 60, 70, and 80xc2xa0xc2xb0C, and three mass flow rates, 0.166, 0.249, and 0.332xc2xa0kgs. The results showed that the HCHE was compatible with the regular heat sources of the TES unit (including solar collectors and heat pump systems). The temperature distribution of the water in the fish tank, from 26.75 to 30xc2xa0xc2xb0C, was suitable for maintaining the health of warmwater fish. To heat 3.4xc2xa0m3 of the fish tank water from 24.5 to 28xc2xa0xc2xb0C, case 6 (where the temperature and mass flow rate of hot water were 70xc2xa0xc2xb0C and 0.332xc2xa0kgs, respectively) obtained the best results during a period of 26xc2xa0min, usable heat transfer rate of 31.8xc2xa0kW, and thermal efficiency of 76.1%. On the contrary, the results for case 1 (where the temperature and mass flow rate of hot water were 60xc2xa0xc2xb0C and 0.166xc2xa0kgs, respectively) were 70xc2xa0min, 11.8xc2xa0kW, and 57.5%, respectively.

On Optimal Energy Consumption Control Method for Tail Fin Bionic Robotic Fish The endurance ability is an important factor to be considered in the practical application of bionic robotic fish. By designing an optimal energy consumption control method, the energy consumption of robotic fish can be effectively reduced. In this paper, the structural characteristics of the tail fin bionic robotic fish are abstracted through the motion analysis of the tail fin fish. On this basis, a simplified dynamic and kinematic model of the robotic fish and a calculation method of energy consumption are established. Then, by changing the oscillation amplitude and frequency of the tail, the change law of the swimming speed is obtained. It is also found that the energy consumption is positively correlated with the swimming speed in general. In order to get the lowest energy consumption swimming mode of robotic fish at different swimming speeds, a series of optimal energy consumption points are obtained at the interval of 0.05ms. The control method of optimal energy consumption of robotic fish is designed by analyzing its distribution law.