Industrial Furnace Technology

To increase ener­gy and resour­ce effi­ci­en­cy in ther­mopro­ces­sing plants, it is essen­ti­al to have a tho­rough under­stan­ding of the heat trans­fer and flu­id dyna­mics invol­ved. For this pur­po­se, the pro­ces­ses are model­led and sub­se­quent­ly inves­ti­ga­ted and optimized.

The rese­arch group ope­ra­tes a lar­ge num­ber of test rigs, which are equip­ped with exten­si­ve and modern mea­su­re­ment tech­no­lo­gy. Fur­ther­mo­re, the expe­ri­men­tal methods are com­ple­men­ted by ana­ly­ti­cal, (semi-)empirical models and nume­ri­cal simu­la­ti­ons (CFD/ FEM). A com­bi­na­ti­on of expe­ri­men­tal, ana­ly­ti­cal and nume­ri­cal inves­ti­ga­ti­ons enables a com­pre­hen­si­ve repre­sen­ta­ti­on of the phy­si­cal processes.

Heat transfer in thermoprocessing plants

The heat trans­fer during hea­ting or coo­ling of the mate­ri­al in an indus­tri­al fur­nace has a direct influence on the effi­ci­en­cy of the plant. Two main heat trans­fer mecha­nisms are invol­ved — (forced) con­vec­tion and ther­mal radiation.

The inves­ti­ga­ti­on on forced con­vec­tion focu­ses on the flow of the flu­id in ther­mopro­ces­sing plants. In addi­ti­on to the inves­ti­ga­ti­on of the macro­sco­pic flow indu­ced by fans, the local flow in the vici­ni­ty of the mate­ri­al is also high­ly rele­vant. It decisi­ve­ly deter­mi­nes the achie­va­ble heat trans­fer coef­fi­ci­ents bet­ween the mate­ri­al and the flu­id. The­se influence the hea­ting and coo­ling rates that can be achie­ved in the pro­cess. Cur­rent rese­arch work is con­cer­ned with both gas and water quen­ching sys­tems. The coo­ling rates that can be achie­ved under dif­fe­rent aspects and pro­blems that have a direct influence on the mate­ri­al pro­per­ties are considered.

In the field of radia­ti­on-domi­na­ted pro­ces­ses, the rese­arch group is working on radia­ti­on models that allow the con­side­ra­ti­on of arbi­tra­ry two- and three-dimen­sio­nal geo­me­tries. The­se are used for the deve­lo­p­ment of pro­cess models, for exam­p­le for fle­xi­ble batch plan­ning and pre­dic­tion of the hea­ting time of the mate­ri­al, in order to keep pro­cess times as short as pos­si­ble and thus energy-efficient.

Fluid-structure interaction

Flow in indus­tri­al fur­naces can lead to unde­si­ra­ble phe­no­me­na such as nozz­le-indu­ced strip vibra­ti­on in anne­al­ing lines or hori­zon­tal strip flo­ta­ti­on fur­naces, which in turn can cau­se dama­ge to the mate­ri­al or the fur­nace. Like­wi­se, in com­bi­na­ti­on with high tem­pe­ra­tures, important plant com­pon­ents such as fans, can be dama­ged under cer­tain ope­ra­ting con­di­ti­ons (e.g. due to eigen-oscil­la­ti­ons at a given rota­tio­nal speed). In addi­ti­on to expe­ri­men­tal inves­ti­ga­ti­ons, the deve­lo­p­ment of relia­ble nume­ri­cal models of such phe­no­me­na is also a key focus.

Highly flexible heat treatment

The department’s own anne­al­ing simu­la­tor enables cus­to­mi­zed heat tre­at­ments to deri­ve an opti­mum anne­al­ing cycle for metal­lic samples. For this pur­po­se, any atmo­sphe­res (from inert gas up to 100 % hydro­gen), as well as rapid hea­ting and coo­ling rates can be set. The modu­lar heat tre­at­ment faci­li­ty also ope­ra­ted by the group allows, in addi­ti­on to coo­ling with air, coo­ling with water under arbi­tra­ry nozz­le fields, as well as sel­ec­ti­ve tem­pe­ring of samples with dimen­si­ons of max. 300 mm x 200 mm. With the­se test faci­li­ties, mate­ri­als tech­no­lo­gy is lin­ked to the pro­cess, which enables the detail­ed inves­ti­ga­ti­on of indi­vi­du­al pro­blems, but also the sub­se­quent trans­fer to the indus­tri­al plant.

Structural integrity, lifetime optimization and prediction

In addi­ti­on to the con­side­ra­ti­on of heat trans­fer and flu­id dyna­mics in ther­mopro­ces­sing plants, the ther­mal­ly indu­ced stress dis­tri­bu­ti­on of the plant com­pon­ents (e.g. radi­ant tubes, nozz­le boxes) also plays a role in many appli­ca­ti­ons. By app­ly­ing nume­ri­cal methods (e.g. FEM), ther­mal stres­ses can be cal­cu­la­ted as a func­tion of the tem­pe­ra­tu­re dis­tri­bu­ti­on and the res­traint situa­ti­on, and com­po­nent fail­ures can be pre­dic­ted. A com­bi­na­ti­on with creep models allows the exten­si­on of ther­mal stress models to life­time pre­dic­tion models.