Study Of Lightweight Design And Pressure Loading Capacity Of All-Welded Plate Heat Exchanger

Plate heat exchangers (PHEs) are widely used in many applications because of their compact structure as well as high efficiency. Turbulent flow can be achieved with lower Reynolds number. All-welded plate heat exchangers are more capable for higher pressure and temperature, which gives the all-welded plate heat exchangers much wider applications in engineering. In this thesis, all-welded plate heat exchanger is studied for its structure strength and design approaches.(1) Finite element analysis was chosen to calculate the strength of all-welded plate heat exchanger. Solid element model was established base on ANSYS APDL Product. Stress analysis was carried out under the pressure loading with the normal temperature. Strength assessment was conducted based on JB/T4732. We found that the stresses at tension rods and left nozzles exceed the limit for the initial design. And the stresses at other parts are far below the limit.(2) Due to the complex structure, stress classification is not easily performed. Limit analysis is an alternative choice. With the finite element model, both limit loads at the shell-side as well as the plate-side are obtained. Results found that the allowable shell-side limit load is 2.6MPa and allowable plate-side limit load is 3.524MPa, which are larger than their design pressures. This means that the strength of all-welded plate heat exchanger meet the strength requirements.(3) Light-weight design was conducted for the present structure. It is found that when the thickness of pressing plate is 30mm, right and left arc plates is 12mm and top and bottom arc plates is 8mm, this all-welded plate heat exchanger still meets the strength requirements. On the another hand, load-carrying capability analysis was also conducted. By taking four different measures, i.e. increasing the thickness, applying nozzle reinforcement, increasing the height of strengthening rib and increasing the diameter of tension bars, the allowable shell-side limit load and allowable plate-side limit load can be raised. For example, when the the thickness of the pressing plate, arc plate and tubes are respectively 60mm,20mm and 14mm, the height of the strengthening ribs is increased by 60mm and the diameter of tension bars is 34mm, the allowable limit loads on the shell-side and plate-side can reach 6.22MPa and 4.907MPa, respectively.(4) The heat exchanger plates are also studied. The displacement of two plates under the pressure of 1.8MPa is very small and the corrugates on the plates will not be flattened. The compensation ability for the thermal expansion of corrugated plate is better than the plane plate with the same size. Except the discontinuous regions, the average thermal stress of corrugated plate is lower than plane plate. The support reaction force of corrugated plate is also much smaller than plane plate under the same tensile loading. An equivalent Young's modulus is proposed when replacing the corrugated plate with plane plate for deformation computation.