Technotrans cooling solution for injection moulding

The invest­ment at the Waren­dorf site, the so-called “Tech­nol­o­gy Cen­ter Plas­tics”, became nec­es­sary when an old closed sys­tem from Miele with a hybrid evap­o­ra­tive cool­er was sent into well-earned retire­ment after 25 years. The new solu­tion enables the pro­vi­sion of water at a tem­per­a­ture of 30 °C even at high out­side tem­per­a­tures of up to 35 °C.

In the sys­tem used by the group until then, the water came into direct con­tact with the ambi­ent air and led to a high lev­el of dirt enter­ing the treat­ed make-up water. This is because the cool­ing prin­ci­ple is based on the evap­o­ra­tion effect. Water is con­tin­u­ous­ly lost in the process. In addi­tion, the cir­cu­lat­ing water must be elab­o­rate­ly fil­tered and inoc­u­lat­ed with water addi­tives. Exten­sive mon­i­tor­ing due to an increased risk of con­t­a­m­i­na­tion, for exam­ple with legionel­la and oth­er bac­te­ria, makes this an increas­ing­ly impor­tant and main­te­nance-inten­sive task.

The alter­na­tive to open cool­ing sys­tems are closed free-cool­ing sys­tems that dis­si­pate heat to the envi­ron­ment via an air-water heat exchang­er. They come with­in about 5 Kelvin of the out­side tem­per­a­ture. So if a water sup­ply tem­per­a­ture of 30 °C is required, this con­ven­tion­al tech­nol­o­gy will work with­out any prob­lems up to an out­side tem­per­a­ture of 25 °C. If it is warmer out­side, addi­tion­al cool­ing must be added via spray­ing, the addi­tion of city water or an addi­tion­al refrig­er­at­ing machine in order to main­tain the 30 °C water sup­ply temperature.

The spe­cial fea­ture of the new Reis­ner solu­tion is its com­bi­na­tion with the PAD sys­tem, which also enables cool­ing at high out­side tem­per­a­tures via humid­i­fied hon­ey­combs. This not only saves Miele time and mon­ey, but also meets the com­pa­ny’s own demand for high-qual­i­ty solu­tions. Alexan­der Wibe, Head of Plant Tech­nol­o­gy, describes this as fol­lows: “We were look­ing for an ener­gy-sav­ing solu­tion that also leaves noth­ing to be desired in terms of tech­nol­o­gy. The cool­ing sys­tem had to be of high qual­i­ty and rely on well-known com­po­nents. Low-main­te­nance, reli­able and effi­cient, cou­pled with a 24-hour ser­vice in the event of an emer­gency — that was the over­all pack­age required.”

From Waren­dorf, the com­pa­ny sup­plies all appli­ance plants of the Miele Group. The prod­uct range includes com­plex assem­blies such as wash­ing machine doors or dry­er sieves, mul­ti-com­po­nent parts and parts with high-gloss sur­faces such as hoover hous­ings. Accord­ing to its own state­ment, 60% of the plas­tic parts installed in Ger­man Miele appli­ance plants come from Waren­dorf. In addi­tion, the plant, which was found­ed in 1975 and employs around 300 peo­ple, over­sees plas­tics pro­duc­tion at Miele sites in Uničov (Czech Repub­lic), Dong­guan (Chi­na) and Ksaw­erów (Poland).

The deci­sion in favour of Reis­ner was ulti­mate­ly an easy one: “From costs to tech­nol­o­gy to com­pre­hen­sive ser­vice, Reis­ner offered the best pack­age,” says Wibe. In the uncom­pli­cat­ed and cus­tomer-ori­ent­ed plan­ning phase, the Reis­ner project team explained which indi­vid­ual solu­tion they would like to use.

Close partnership with individual solution

The spe­cial fea­ture is the closed sys­tem in which a V‑shaped, self-drain­ing free cool­er is installed. The hon­ey­comb struc­ture of the PAD sys­tem is only moist­ened with city water when high out­side tem­per­a­tures of around 25 °C and above make this nec­es­sary. When the air flows through this struc­ture, it cools down — as is usu­al with adi­a­bat­ic cool­ing. Then the process heat is dis­si­pat­ed to the cooled air by means of a CU/Al heat exchang­er (not by evaporation).

“The deci­sive fac­tor here is that the spray­ing water does not come into con­tact with the heat exchang­er. The heat is almost com­plete­ly dis­si­pat­ed via the air, mak­ing the sys­tem a reli­able and cost-effec­tive cool­ing solution.”

- Gün­ter Sareyko, Head of Sales at Reis­ner Cool­ing Solu­tions GmbH

In total, the new sys­tem offers a recool­ing capac­i­ty of up to 500 kW and reli­ably ensures the desired process tem­per­a­ture at up to 35 °C out­side tem­per­a­ture. Reis­ner has also thought along when it comes to main­te­nance. Easy replace­ment of the PADs, which already pro­vide a ser­vice life of three to five years depend­ing on use, was just as impor­tant as min­imised water con­sump­tion and the use of durable materials.

“Miele not only saves ener­gy through its spe­cial design, the com­po­nents them­selves are also designed to be ener­gy-sav­ing,” says Reis­ner. The fail-safe dual-pump sys­tem with a vol­ume flow of up to 87 m³/h is speed-con­trolled, as are the 14 fans with EC motors. The humid­i­fi­ca­tion itself is also mul­ti-stage. The built-in return fil­ter works com­plete­ly pres­sure­less and can be changed dur­ing oper­a­tion. Reis­ner thus reduces the ener­gy required in each process step to a minimum.

After the sys­tem has been run­ning since Octo­ber 2020, Wibe is more than sat­is­fied: “The quick deliv­ery and com­mis­sion­ing dur­ing oper­a­tion with­out the instal­la­tion of rental refrig­er­a­tion were opti­mal. Reis­ner always worked clean­ly and con­sci­en­tious­ly, so our expec­ta­tions were absolute­ly met.” This also includes, for exam­ple, the con­trol cab­i­net con­struc­tion accord­ing to Miele spec­i­fi­ca­tions or the uncom­pli­cat­ed com­mu­ni­ca­tion dur­ing the entire project.

Wibe is not yet able to pre­cise­ly quan­ti­fy the cost and time sav­ings, but is very pos­i­tive after the first expe­ri­ences. “The ear­ly find­ings show that ener­gy con­sump­tion has dropped sig­nif­i­cant­ly. The plant runs very sta­bly and we have man­aged to com­plete­ly dis­pense with the use of chemicals.”

Additional optimisation with full-flow filtration

The group’s high stan­dards are also evi­denced by the deci­sion to use an addi­tion­al fil­ter solu­tion and chem­i­cal-free water treat­ment. Even after a short peri­od of use, the water qual­i­ty showed a steady improve­ment due to the water treat­ment with full-flow fil­tra­tion in the return flow. The sys­tem dis­solves lime and cor­ro­sion com­pounds by means of low-fre­quen­cy elec­tro­mag­net­ic alter­nat­ing fields. These can then be fil­tered out of the water accord­ing­ly. “Miele stands for qual­i­ty. We are there­fore very pleased that we can con­tribute to this image with our cool­ing exper­tise,” Gün­ter Sareyko sums up.