Traveling LHR-PVG-TPE-ICN-PVG-LHR

First and the most important is that your itinerary is definitely eligible for visa free transit in Shanghai both ways and you don't need any kind of visa.

Now, 144 hour visa free transit and not 144 hour transit visa is valid from the time of your scheduled arrival in Shanghai, until your scheduled departure from Shanghai and this transit option expires exactly when you board the plane or better to say when you have de jure left China. So, you will get new visa free transit scheme upon your second stop in Shanghai. They are not related and you can get those schemes as much as you want. There is no limit. The limit is just your itinerary and your citizenship. In your case, both conditions are fulfilled.

You will be definitely qualified for 144 hour visa free transit during your first stop and during your second stop for 24 or 144 hour visa free transit. I cannot clearly count your entire transit time during your second stop in Shanghai. Anyway, this is easy. If your entire transit time will be less than 24 hours, you will be eligible for 24 hour visa free transit and if your entire transit will be just a minute longer than 24 hours, you will be again eligible for 144 hour visa free transit. You count your entire transit time from your scheduled arrival in China, until your scheduled departure from China. In any case, you will stay in Shanghai visa free both ways.

Just don't forget to print out your flight tickets and your accommodation booking confirmations.

Got it! Thank you very much !!! 👍👍👍