It is practically difficult to upgrade cooler in this model because it is essentially small form factor.  you could in theory install a Dell premium tower cooler for XPS8940 in it, but then you cannot close the side panel.  other options to consider is better low profile LGA1151 cooler from third party or liquid cooling.[IMAGE][IMAGE]  
Hi I've got a 4 year old (nearly) Inspiron 3470 with an i5-8400 CPU [NAME].80GHz. with 8GB ram. It now needs a couple of upgrades to keep it going for a year or so then I'll look for a new system. When I bought it, there were a couple of other options  i3 and i7 processors I've upgraded to 32GB of ram (working fine) I'm looking to upgrade to a 9th Gen i7 CPU which is  more "reasonable" in cost now. Which of the i7 9th Gen processors will work with it?  There are various flavours of the i7-9000 9th Gen with a letter afterwards released during 2018 and 2019 i7-9000K i7-9000KF etc. Which of the 9700's are compatible? also is there any bios (I'm running 2.23.0) or other upgrades necessary to run the i7 processors thanks for reading and appreciate your replies if any      
Inspiron 3470 i5-8400 CPU @2.80GHz. with 8GB ram