Does the Torque Converter heat engine while idling??

It's all just a giant physics equation. Heat is generated by a number of things, and it is dissipated by a number of things(variables). IMO your car is operating well within the parameters established for it. If you just want to know why or want to learn, you will have to examine each component individually to find out how they operate, and how they operate together. Not too big a deal, but too much for this thread. You pretty much got the long and the short of it in this thread.