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The new diffuser AxiTop reduces energyconsumption and is easily retrofittedthe conversion into this useful power. The largestloss factor in the process is the dynamic outputcomponent (P ud ) of air performance, which is alsoknown as exit loss. This is made up of the productof air flow and dynamic pressure. The motorand fan manufacturer ebm-papst has now pickedup this issue and has developed a new kind ofdiffuser, the AxiTop. Replacing the conventionalguard grille of the fan by the AxiTop diffuser(Fig. 2, page 10) significantly reduces losses atthe air outlet. Efficiency increases while operatingnoise is reduced at the same time. In principle,the diffuser works like a reverse nozzle, asfollows:Dynamic energy converted into static pressureEvery medium is only able to absorb a certainamount of heat energy for each degree Kelvin.The possible temperature difference and theamount of heat to be expelled define the coolingair flow required. This air volume has to be deliveredby a fan through the heat exchanger underconsideration. To do this, a pressure differentialis necessary which is sufficient to overcome theflow resistance of the exchanger. Normally, thedelivered air flows at high speed from the exit sideof the fan and dynamic pressure (p fd ) dissipatesinto the environment. Dissipation means that thekinetic energy of the flow is converted into turbulenceand then due to friction into heat thattechmag 01°20139