Not many people think of the HVACR industry or of service technicians in general as being scientists.
Yet, the entire refrigeration process works by thermodynamic principles and laws that few laypeople understand. And when it comes to pulling a vacuum in an enclosed compression-cycle system, even technical people who have worked in the industry for many years may not fully grasp what is going on or what they are trying to accomplish. In fact, for this reason, many are trying to do the job without the proper tools and by following processes that work poorly or not at all.