I would recommend you install the Dell Command Power Manager on bios A00, set the fan profile to quiet, and then upgrade the bios. You can find the power manager on the Dell support page when you enter your service tag. Note the Dell Support download portal is screwed up and won't show you all available downloads at once. So you need to initiate a few downloads and others will eventually show up. May be a browser issue. Not sure. As far as finding A00 I found it after a Google search. It would be nice if it was available on the download page. Good luck!
I'm also a victim of this fan noise issue. I purchased my XPS 13 (touch screen- Core i7) last week. A dell onsite technician came and replaced the fan and the heat-sink. The problem has not solved though. Thinking of returning the product back to Dell next week. This seems to be a manufacturing defect.
Mine is 15" DELL XPS L521X. CPU fan is so loud and when connecting to external dual screen through thunderbolt and HDMI. I've updated the BIOS but still the problem persist. I hope someone out there can help me. Thanks!