Honestly, this is a perfect use-case for the old MacPros (2009-2012) – particularly with the dual Xeon configuration [†] – they are notorious for their turboprop fans and exhorbitant powerbills.

You can usually get one for free (or less, "doing them a favor") via social media. I just gave one away (because the receiver had a better use for it than my XMR mining).

Make sure you use fan-boosting software, to keep everything less than 80°C. See you on the network!

[†] A MacPro5,1 with 12 cores will hash at about half the rate of a modern AMD Ryzen7 chip, using twice the electricity – perfect for your localized toe-heater (they also have incredible airflow, with MacFanControl software; in Linux, disconnect the PCI fan [∑] and the four CPU fans will full-blast). GPU is irrelevant for monero-mining (the stock GT120 [or 57X0] is perfect for this).

[∑] it's useless – or you can disconnect CPU_B_BOOST (fan), which is even more useless (but more-difficult/dangerous: do NOT disconnect _A_)... this makes the BIOS full-blast all remaining fans

NB: Newer i5s (mid-2010s) will hash at identical rates, but use much less power [not ideal for this situation] – but they tend to not have great heatsinks so you may have to run less cores.