There are three types of tapas in a human being , when we meditate with a goal to be liberated from wordly matters we are actually removing all three gunas (satva,rajas,tamas) and become nirguna, to attain the divine position in lotus feet of lord.
In bhagwat-mahapuran one shloka describes shri krishna as
Sacchidananda rupaya jagadutpayadi hetave
tapatraya vinashaya shri krishnaya vayam namah.
The tapa means heat and that's exactly what we libreate when we meditate and do hari kirtan as described in shloka.When we see sacchidananda swaroop of lord krishna who is reason for creation and destruction of this world , we burn our karmas and release three type of tapas and then we see lord in a nirguna avastha.
Refrence for tapas and it's types.