A 2D shell-and-tube heat-exchanger is used to exemplify essential ideas of HEXAGON model of D.B.Spalding and S.V. Zhubrin, which is probably the first to show how the thermo-hydraulics of the shell-side and tube-side fluids could be simultaneously computed with the displacements and thermal stresses in tubes and shell to be included in a SFT, Solid-Fluid-Thermal, heat-exchanger analysis.
The case illustrates the use a single computer program to calculate from the partial-differential equations governing relevant fluid processes the distributions of:-
* shell-side fluid velocity components;
* the corresponding temperatures and pressures;
* the tube-side fluid velocity components;
* the corresponding temperatures and pressures;
* the tube metal temperatures; and
* the displacements and stresses in the tubes and the shell.
The heat exchanger considered is an imaginary one, having two baffles within the shell, with the U-bend tubes arranged in array and header distribiting the in-fluid between the tubes and collecting out-fluid.
No attempt has been made to pick-up and implement the actual resistance formulae which are widely used in thermal engineering. But because PLANT is used to represent them, the artificial formulae can be easily replaced by required ones.
The heat exchanger is a rectangular box, 2.0m high, 1m wide and 1m long. It consists of the header, the hight of which is 0.8m and shell closed at the bottom and open at the top. The header is divided into two halfes by a vertical plate.
The shell is uniformly filled with the tubes. The tube fluid (water) enters the header through the inlet at its west wall, flows downwards in west half of the shell, turns through the U bend at the bottom and rises upward in the other shell half to enter the east half of the header going out through the outlet at header east side.
The shell fluid ( air ) entering the shell through the inlet at the west wall is made to pass between two baffles in a zig-zag manner, until it goes out through the outlet at the top of the west wall of shell.
Only X-Y plane of the exchanger is included in the calculation domain, because of 2D-nature of analysis.
A uniform 26*32*1 grid is used, to cover computational space.