Re: re: I blame the fact that they are the marketing department.
The sensible thing to do in that situation is move the portable aircon to fan only and blow air so that you exhaust the room air and bring in the cooler evening , night time air.
Air changes and cooling the thermal mass is key to performance depending on your building structure and insulation levels but you should be able to change the room air pretty fast to the external temperature and slowly reduce the wall temperature down (sometimes called the pseudo constant - but that would irritate too many pedants. And don't get me started on 'coolth' units!)
In buildings with decent insulated thermal mass this is used for pre-cooling too - bring the core temperature a few degrees below and use it as a heat sink in the day.
Free air cooling has become much more widely used these days (including data centres).
It is not correct that you should never use outside air in unless other air quality factors - dust , humidity etc were at play. Even then outside air is brought in, just in a carefully controlled way.