The Lumped Heat Capacity approximation should be the first thing you try for every Transient Conduction problem. Just calculate the Biot Number, using the Characteristic Length, and if Biot Number is small, you are good to go.
This Lumped Capacitance Example Problem also comes with a mini-lecture to explain what the lumped capacitance model actually means, which will also help you decide whether or not this simplification is appropriate for your specific problem.
Bookmark my full Heat Transfer playlist:
https://www.youtube.com/playlist?list=PLZEGV3UcXTiN0jCC42I-RHpnLE22hia9H
CHAPTERS
0:00 3 Kinds of Transient Conduction Problems
0:36 What is Annealing?
2:31 What is the Biot Number?
3:06 What is Lumped Capacitance?
4:07 Where to lookup conduction coefficient
5:49 When can you use Lumped Heat Capacity Method?
7:44 Lumped Capacitance Equation
10:37 Find Total Heat transferred
