The undulating fin propulsion system is an instance of the bio-inspired propulsion systems. In the current study, the swimming motion of a squid-like robot with two undulating side fins, mimicking those of a Stingray ...The undulating fin propulsion system is an instance of the bio-inspired propulsion systems. In the current study, the swimming motion of a squid-like robot with two undulating side fins, mimicking those of a Stingray or a Cuttlefish, was investigated through flow computation around the body. We used the finite analytic method for space discretization and Euler implicit scheme for time discretization along with the PISO algorithm for velocity pressure coupling. A body-fitted moving grid was generated using the Poisson equation at each time step. Based on the computed results, we discussed the features of the flow field and hydrodynamic forces acting on the body and fin. A simple relationship among the fin＇s principal dimensions was established. Numerical computation was done for various aspect ratios, fin angles and frequencies in order to validate the proposed relationship among principal dimensions. Subsequently, the relationship was examined base on the distribution of pressure difference between upper and lower surfaces and the distribution of the thrust force. In efficiency calculations, the undulating fins showed promising results. Finally, for the fin, the open characteristics from computed data showed satisfactory conformity with the experimental results.展开更多
This paper theoretically analyses fin efficency of heat exchanger surface under frosting condition. From the compasrison of some fin efficiency functions, shortages have beenpointed out. On the basis of linearization ...This paper theoretically analyses fin efficency of heat exchanger surface under frosting condition. From the compasrison of some fin efficiency functions, shortages have beenpointed out. On the basis of linearization of eothalpy of saturation humid air, a new fin efficiency function is developed. New function synthetically considers the effect of temperaturedistribution on fin surface and the heat transfer intensify of mass transfer so that it can moreaccurately reflect the fin effect to heat transfer performence. Analysis result shows that thefin efficiency is independent on air relative humidity in certain temperature range.展开更多
This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for differ...This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for different heat transfer coefficient (h = 20 W/m2K to h = 80 W/m2K) and air relative humidity over the full range from φ= 0 % to φ= 100%. It is shown that the fin efficiencies of the staggered arrangement are higher than those for the in-lined arrangement, and the fully wet fin efficiency is 10~20% lower than that for a dry fin. The conventional 1-D sector method underestimates the fin efficiency up to 4 % as compared to the 2-D analysis.展开更多
文摘The undulating fin propulsion system is an instance of the bio-inspired propulsion systems. In the current study, the swimming motion of a squid-like robot with two undulating side fins, mimicking those of a Stingray or a Cuttlefish, was investigated through flow computation around the body. We used the finite analytic method for space discretization and Euler implicit scheme for time discretization along with the PISO algorithm for velocity pressure coupling. A body-fitted moving grid was generated using the Poisson equation at each time step. Based on the computed results, we discussed the features of the flow field and hydrodynamic forces acting on the body and fin. A simple relationship among the fin＇s principal dimensions was established. Numerical computation was done for various aspect ratios, fin angles and frequencies in order to validate the proposed relationship among principal dimensions. Subsequently, the relationship was examined base on the distribution of pressure difference between upper and lower surfaces and the distribution of the thrust force. In efficiency calculations, the undulating fins showed promising results. Finally, for the fin, the open characteristics from computed data showed satisfactory conformity with the experimental results.
文摘This paper theoretically analyses fin efficency of heat exchanger surface under frosting condition. From the compasrison of some fin efficiency functions, shortages have beenpointed out. On the basis of linearization of eothalpy of saturation humid air, a new fin efficiency function is developed. New function synthetically considers the effect of temperaturedistribution on fin surface and the heat transfer intensify of mass transfer so that it can moreaccurately reflect the fin effect to heat transfer performence. Analysis result shows that thefin efficiency is independent on air relative humidity in certain temperature range.
基金Financial support for this work was provided by the "National Science Council of Taiwan", under contract NSC 90-2212-E006-125.
文摘This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for different heat transfer coefficient (h = 20 W/m2K to h = 80 W/m2K) and air relative humidity over the full range from φ= 0 % to φ= 100%. It is shown that the fin efficiencies of the staggered arrangement are higher than those for the in-lined arrangement, and the fully wet fin efficiency is 10~20% lower than that for a dry fin. The conventional 1-D sector method underestimates the fin efficiency up to 4 % as compared to the 2-D analysis.
