Improvement of heat transfer in tube-bundle heat exchangers by using structured tubes

The aim of the rese­arch pro­ject is to impro­ve the ener­gy effi­ci­en­cy and eco­no­my of gas-fired indus­tri­al fur­nace sys­tems with cen­tral air pre­hea­ting. This goal is to be achie­ved by incre­asing the sur­face area and impro­ving the heat trans­fer of the indi­vi­du­al tube bund­les in a cen­tral recup­er­a­tor. For this pur­po­se, a pro­cess rou­te for the pro­duc­tion of struc­tu­red tube bund­les is to be deve­lo­ped based on pro­ces­ses for the mate­ri­al-pre­ser­ving struc­tu­ring of sheets. The intro­duc­tion of a struc­tu­re in various com­pon­ents has many advan­ta­ges: Struc­tu­red recup­er­a­tor tubes have an increased effi­ci­en­cy com­pared to con­ven­tio­nal smooth recup­er­a­tor tubes due to the lar­ger heat trans­fer­ring sur­face. This leads to impro­ved heat trans­fer. The struc­tu­red tubes can be instal­led in both old and new sys­tems wit­hout any spe­cial design effort. Due to the design, direct retro­fit­ting in old sys­tems to increase the effi­ci­en­cy is possible.

Figu­re of a sim­pli­fied CFD model for the inves­ti­ga­ti­on of struc­tu­red tubes in recuperators

Based on the struc­tu­ring of the sheets, the inves­ti­ga­ti­on of the pro­cess steps sui­ta­ble for series pro­duc­tion for trans­forming the sheets into sui­ta­ble tube bund­les is car­ri­ed out. The­se steps are sup­port­ed by simu­la­ti­ons of the flui­dic, mecha­ni­cal and ther­mal effects of the struc­tu­ring depen­ding on the struc­tu­ring depth on the recup­er­a­tor per­for­mance. An inter­me­dia­te goal is the deter­mi­na­ti­on of the ide­al struc­tu­re dimen­si­ons and their pro­duc­tion. The results obtai­ned will be used to pro­du­ce a demons­tra­tor, which will initi­al­ly be used in a test rig. Based on the data obtai­ned, it will be pos­si­ble to adapt the struc­tu­re and the manu­fac­tu­ring method.