{"id":7743,"date":"2013-07-02T15:08:12","date_gmt":"2013-07-02T13:08:12","guid":{"rendered":"https:\/\/mag.ebmpapst.com\/en\/?p=7743"},"modified":"2025-11-11T11:02:03","modified_gmt":"2025-11-11T10:02:03","slug":"axitop-less-noise-and-more-efficiency","status":"publish","type":"post","link":"https:\/\/mag.ebmpapst.com\/en\/industries\/refrigeration-ventilation\/axitop-less-noise-and-more-efficiency_7743\/","title":{"rendered":"AxiTop \u2013 Less noise and more effi\u00adciency"},"content":{"rendered":"

For refrig\u00ader\u00ada\u00adtion and cooling equip\u00adment, the heat gener\u00adated in the circu\u00adla\u00adtion process has to be trans\u00adferred to the ambient air via a heat exchanger. To accom\u00adplish this, fans move cool air through a heat exchanger and allow the heat to dissi\u00adpate. There is a whole range of options for designing and config\u00aduring espe\u00adcially effi\u00adcient, quiet and durable fans. A new, passive compo\u00adnent, the so-called diffuser, provides for a substan\u00adtial improve\u00adment in effi\u00adciency and noise. Its pres\u00adsure-boosting effect minimises exit losses and makes it easier to adapt the fan to commer\u00adcially avail\u00adable heat exchangers.
\nVenti\u00adlation and air-condi\u00adtioning units usually run in contin\u00aduous oper\u00ada\u00adtion, or at least with long oper\u00adating cycles. That make maximum economy with the input drive energy impor\u00adtant, for every addi\u00adtional watt costs money and impacts the envi\u00adron\u00adment. For that reason, energy effi\u00adciency is an impor\u00adtant crite\u00adrion when choosing a fan. Today, statu\u00adtory stip\u00adu\u00adla\u00adtions also play a role. The effi\u00adcient use of energy and resources is and will remain a global objec\u00adtive for the decades ahead. In Europe, the first tier of the ErP Direc\u00adtive became effec\u00adtive as of January 1, 2013. Against this back\u00adground, it is no wonder that ultra-effi\u00adcient EC tech\u00adnology is increas\u00adingly replacing conven\u00adtional AC tech\u00adnology as the fan drive of choice due to its greater effi\u00adciency.<\/p>\n

Exit losses \u2013 the under\u00ades\u00adti\u00admated \u201cenergy guzzlers\u201d<\/h4>\n
<\/a>

Figure 1: Power \ufb02ow of an axial fan with unim\u00adpeded air\ufb02ow<\/p><\/div><\/div>\n

Energy-effi\u00adcient and quiet oper\u00ada\u00adtion of the complete fan is a func\u00adtion of both the motor and the impeller, which the fan uses to move the air volume needed to create the cooling air flow through the heat exchanger. Aero\u00addy\u00adnamic exper\u00adtise is needed when designing the impeller, for example to avoid sepa\u00adra\u00adtions and back\u00adflows which would cause both energy loss and unwanted noise. Even today, the impellers employed in the Green\u00adTech EC fans satisfy the most demanding stan\u00addards. But there is another point which has to be taken into account when consid\u00adering the effi\u00adciency of a fan:
\nThe inherent exit loss for fans with unim\u00adpeded airflow is often an under\u00ades\u00adti\u00admated energy guzzler. Figure 1 shows the power flow of the input drive power Po<\/sub> for an axial fan with unim\u00adpeded airflow. The drive power Po<\/sub> is split into static blower output (Pus<\/sub> = product of the air flow and static pres\u00adsure increase of the fan), which is of use to the user, and various losses caused by the conver\u00adsion into this useful power. The largest loss factor in the process is the dynamic output compo\u00adnent (Pud<\/sub>) of air perfor\u00admance, which is also known as exit loss. This is made up of the product of air flow and dynamic pres\u00adsure. The motor and fan manu\u00adfac\u00adturer ebm-papst has now picked up this issue and has devel\u00adoped a new kind of diffuser, the AxiTop. Replacing the conven\u00adtional guard grille of the fan by the AxiTop diffuser (Fig. 2) signif\u00adi\u00adcantly reduces losses at the air outlet. Effi\u00adciency increases while oper\u00adating noise is reduced at the same time. In prin\u00adciple, the diffuser works like a reverse nozzle, as follows:<\/p>\n

Dynamic energy converted into static pres\u00adsure<\/h4>\n
<\/a>

Figure 2: The AxiTop diffuser from ebm-papst provides for a signi\ufb01\u00adcant improve\u00adment of ef\ufb01ciency and noise. Its pres\u00adsure-boosting effect minimises exit losses and makes it easier to adapt the fan to commer\u00adcially avail\u00adable heat exchangers<\/p><\/div><\/div>\n

Every medium is only able to absorb a certain amount of heat energy for each degree Kelvin. The possible temper\u00ada\u00adture differ\u00adence and the amount of heat to be expelled define the cooling air flow required. This air volume has to be deliv\u00adered by a fan through the heat exchanger under consid\u00ader\u00ada\u00adtion. To do this, a pres\u00adsure differ\u00aden\u00adtial is neces\u00adsary which is suffi\u00adcient to over\u00adcome the flow resis\u00adtance of the exchanger. Normally, the deliv\u00adered air flows at high speed from the exit side of the fan and dynamic pres\u00adsure (pfd<\/sub>) dissi\u00adpates into the envi\u00adron\u00adment. Dissi\u00adpa\u00adtion means that the kinetic energy of the flow is converted into turbu\u00adlence and then due to fric\u00adtion into heat that is often no longer tech\u00adni\u00adcally utilised. With the AxiTop diffuser, much of the dynamic kinetic energy is converted into static pres\u00adsure (pfs<\/sub>) by way of retar\u00adda\u00adtion. Phys\u00adi\u00adcally, this is easy to explain: The total pres\u00adsure gener\u00adated (pf<\/sub>) by a fan is the sum of the static pres\u00adsure pfs and the dynamic pres\u00adsure pfd_cges<\/sub>. In turn, taking the density r into account, the dynamic pres\u00adsure can be split into three speed compo\u00adnents (cylinder coor\u00addi\u00adnates), the axial compo\u00adnent pfd_cax<\/sub>=\u03c1\/2*cax\u00b2<\/sub>, the circum\u00adfer\u00aden\u00adtial compo\u00adnent pfd_cu<\/sub>=\u03c1\/2*cu\u00b2<\/sub> and the radial compo\u00adnent pfd_cr<\/sub>=\u03c1\/2*cr\u00b2<\/sub>.<\/p>\n

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Figure 3: The AxiTop diffuser allows part of the dynamic pres\u00adsure to be converted into useful static pres\u00adsure by retarding the \ufb02ow<\/p><\/div><\/div>\n

In the diffuser, the axial and circum\u00adfer\u00aden\u00adtial compo\u00adnents of dynamic pres\u00adsure (\u03c1\/2*cges\u00b2<\/sub>) are reduced due to the air slowing in the expanding cross section and, due to the conser\u00adva\u00adtion of energy (Bernoulli\u00b4s prin\u00adciple), the usable static pres\u00adsure compo\u00adnent increases (see Fig. 3). Effi\u00adciency can be signif\u00adi\u00adcantly increased in this way if all compo\u00adnents are co-ordi\u00adnated to be aero\u00addy\u00adnam\u00adi\u00adcally opti\u00admised.
\nIn prac\u00adtice, the use of the AxiTop diffuser does not just mean lower energy consump\u00adtion; it also means greater degrees of freedom for the user and for the devel\u00adop\u00adment engi\u00adneer. The diffuser config\u00adu\u00adra\u00adtion can be opti\u00admised for different char\u00adac\u00adter\u00adis\u00adtics, depending on the appli\u00adca\u00adtion concerned. Either a greater blower output is possible with unchanged energy input, or unchanged air perfor\u00admance is possible with lower energy consump\u00adtion. A diffuser can also greatly improve the noise behav\u00adiour. This acoustic improve\u00adment is espe\u00adcially inter\u00adesting when fans are working is a noise-sensi\u00adtive envi\u00adron\u00adment, for example in overnight oper\u00ada\u00adtion in venti\u00adlation and climate control systems in resi\u00adden\u00adtial build\u00adings or in rooms where people meet and where there are also noise protec\u00adtion regu\u00adla\u00adtions to be fulfilled.<\/p>\n

Signif\u00adi\u00adcant poten\u00adtial to be exploited<\/h4>\n
<\/a>

Figure 4: Energy consump\u00adtion and noise devel\u00adop\u00adment are signi\ufb01\u00adcantly lower with unchanged air perfor\u00admance. Blower output is increased and noise reduced with unchanged power input. (Details from an example appli\u00adca\u00adtion)<\/p><\/div><\/div>\n

The poten\u00adtial of the possible energy savings, increased effi\u00adciency and noise reduc\u00adtion provided by an optimal diffuser is substan\u00adtial for common heat exchangers on the market. This has been confirmed in exten\u00adsive test series. Figure 4 illus\u00adtrates a specific example. Replacing a normal fan with a guard grille with the same fan with a support bracket, guard grille and diffuser allows savings of 27 % for energy consump\u00adtion while enabling an oper\u00adating noise level 7.2 dB(A) lower with the same air flow (see Fig. 4).
\nAlter\u00adna\u00adtively, if the greater effi\u00adciency of the fan with differ is exploited, it will deliver about 9 % more air flow with the same input power, and at the same time noise emis\u00adsions will be reduced by 4.9 dB(A) (see fig. 4). This value has been deter\u00admined on an exem\u00adplary customer appli\u00adca\u00adtion. Depending on the indi\u00advidual config\u00adu\u00adra\u00adtion, the opti\u00admised effi\u00adciency can be used either to reduce power input or to increase air perfor\u00admance. So not only does the user save energy during oper\u00ada\u00adtion; the design engi\u00adneer for a climate control system can get by with smaller heat exchanger surface areas. The space needed for the cooling unit can be reduced with unchanged or even improved noise behavior and constant refrig\u00ader\u00ada\u00adtion capacity. The reduc\u00adtion in the space needed is an argu\u00adment which cannot be neglected, above all for larger heat exchangers. A diffuser is even worth\u00adwhile if it subse\u00adquently turns out that the system does not have a suffi\u00adcient refrig\u00ader\u00ada\u00adtion capacity, e.g. in the case of a design error. It enhances the air perfor\u00admance without increasing noise. In such cases, the instal\u00adla\u00adtion of an addi\u00adtional heat exchanger (and the asso\u00adci\u00adated costs) can often be avoided.<\/p>\n

Can be retro\u00adfitted and used in existing wall rings<\/h4>\n
<\/a>

Figure 5 (right): The thrust range is not affected by the AxiTop diffuser. The illus\u00adtra\u00adtion shows the axial \ufb02ow rate with diffuser on the left and without diffuser on the right<\/p><\/div><\/div>\n

Equip\u00adping existing heat exchangers with a diffuser is easy and only requires a few changes to venti\u00adlation and air-condi\u00adtioning units. The diffuser is fitted in place of the guard grille. Existing wall rings can still be used. The AxiTop diffuser from ebm-papst is just 250 mm high so it needs very little space.
\nWith these dimen\u00adsions, the devel\u00adop\u00adment engi\u00adneers have succeeded in achieving a very good compro\u00admise. Phys\u00adi\u00adcally, a diffuser cannot be large enough in order to increase static pres\u00adsure. But dimen\u00adsions which are as compact as possible are required in prac\u00adtice. CFD simu\u00adla\u00adtions combined with para\u00admetric opti\u00admi\u00adsa\u00adtions have produced an excel\u00adlent aero\u00addy\u00adnamic result. The change in the outflow profile causes the flow to split slightly, enabling the thrust range of the fan to be main\u00adtained. Figure 5 shows the different char\u00adac\u00adter\u00adis\u00adtics of the exit speed cax, which is of rele\u00advance for the thrust range, with and without a diffuser.
\nThe new AxiTop diffuser is designed for fans of the sizes 800 and 910. Versions for 500 which are frequently employed with heat exchangers will follow in the near future. It doesn\u00b4t matter whether the fan works with Green\u00adTech EC or with an AC drive. However, in the interest of energy effi\u00adciency, the combi\u00adna\u00adtion with Green\u00adTech EC fans in certainly prefer\u00adable.<\/p>\n","protected":false},"excerpt":{"rendered":"

For refrig\u00ader\u00ada\u00adtion and cooling equip\u00adment, the heat gener\u00adated in the circu\u00adla\u00adtion process has to be trans\u00adferred to the ambient air via a heat exchanger. To accom\u00adplish this, fans move cool air through a heat exchanger and allow the heat to dissi\u00adpate. There is a whole range of options for designing and config\u00aduring espe\u00adcially effi\u00adcient, quiet [\u2026]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"wp_typography_post_enhancements_disabled":false,"footnotes":""},"categories":[91,16,9],"tags":[138,139],"class_list":["post-7743","post","type-post","status-publish","format-standard","hentry","category-erp","category-fans","category-refrigeration-ventilation","tag-retrofit","tag-upgrade"],"acf":[],"_links":{"self":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/7743","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/comments?post=7743"}],"version-history":[{"count":5,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/7743\/revisions"}],"predecessor-version":[{"id":22277,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/7743\/revisions\/22277"}],"wp:attachment":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/media?parent=7743"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/categories?post=7743"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/tags?post=7743"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}