Decrease the temperature of your Mac. Set a temperature you'd find convenient your Mac to stay at, and the application will keep it. Choose one of two modes: the Auto mode, when you just set the target temperature and the Manual mode, when you control your Mac's fans manually.
UltraFan 1.2.2 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free software for Mac OS X is an intellectual property of Luca C.
This free app can be installed on Mac OS X 10.6 or later. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. The most popular version of the application is 1.0. The unique ID for this application's bundle is com.LucaC.UltraFan.
From the developer:
UltraFan is a free cooling tool for your Mac: set a temperature you'd like your Mac to stay at, and let it handle the task. This application uses Apple's suggested safe speeds on a per fan basis. Other thresholds are applied, for the sake of the paranoid.