Numerical Study On Heat Transfer Enhancement Of Spirally Special-shaped Tube And Its PIV Experiment Analysis

The development of energy-saving technologies should be more and more important for economic development, improving the quality of life, and sustainable development strategy in the background of the energy crisis, the domestic energy situation and the adjustment of domestic industrial structure. Shell-and-tube heat exchangers are extensively used in industrial production, especially in the energy-intensive industries. Therefore, it should be favorable for energy saving and emission reduction on condition that the heat transfer performance in tube-side and shell-side of shell-tube heat exchanger could improve significantly, meanwhile the pressure drop in tube-side and shell-side of shell-tube heat exchanger could just increase slightly or even decrease. From these reasons, we design new-type heat transfer elements and shell-tube heat exchangers which the designed heat transfer elements are used in, and study on the heat transfer and flow characteristics in these elements and shell-tube heat exchangers in order to acquire good thermal-hydraulic performance on the basis of the convective heat transfer optimal theory of minimum dissipation and physical quantity synergy principle.The convective heat transfer optimal theory of minimum dissipation and physical quantity synergy principle are the theoretical foundation for the designs and analysis of the new-type heat transfer elements. The convective heat transfer optimal theory of minimum dissipation indicates that the fluid which come into being longitudinal rotation flow with single or multi vortexes will improve the overall thermal-hydraulic performance. The physical quantity synergy principle reveals the relationship between heat transfer and pressure drop in fluid convective process, and interpret the essential characteristics of heat transfer ehancement and pump power comsuptions.Two new-type heat transfer elements-spirally corrugated tube with deep grooves and elliptical eccentric spiral tubes, and three new-type shell-tube heat exchangers-Rod-baffle heat exchanger with spirally corrugated tubes (RBHXSCT), shell-tube heat exchanger with self-supporting spirally corrugated tubes (STHXSSCT) and shell-tube heat exchanger with self-supporting elliptical eccentric spiral tubes (STHXSEEST). The numerical study on spirally corrugated tubes show that the longitudinal rotational flow can be developed in spirally corrugated tube with deep grooves and the PEC value can achieve2.98which demonstrate fluid in these tubes can acquire good thermal-hydraulic performance. The numerical study on RBHXSCT show that the EEC value in RBHXSCT with one-start spirally corrugated tubes can achieve1.35, thereby making this heat exchanger promising to be widely applied in various industries. The numerical study on STHXSSCT show that the EEC value in STHXSSCT can achieve2.41which make this heat exchanger promising to be widely applied in various industries. The numerical study on elliptical eccentric spiral tubes show that the longitudinal rotational flow can be developed in these tubes and the PEC value can achieve2.52which demonstrate fluid in these tubes can acquire good thermal-hydraulic performance. The numerical study on STHXSEEST show that the EEC value in STHXSEEST can achieve11.7which make this heat exchanger promising to be widely applied in various industries.The fluid velocity field characteristics in spirally corrugated tuebs are measured by stereo partical image velocimetry (Stereo-PIV) systems. The experimental results demonstrate the fluid in spirally corrugated tubes with deep grooves can come into be longitudinal rotational flow with single vortex.