If the unit is heating a room as was demonstrated in figure 1 and the COP is 10, what would happen if one built a brick oven structure around the unit making it more difficult for the heat to escape?
Would it reach a higher temperature and a higher COP?
Will it stop working at some higher temperature caused by this procedure?
If it keeps pumping out the same amount of excess heat and you insulated it with a brick oven structure, it will get hotter. If the reactor produces additional excess heat at higher temperatures, it could thermally run away by getting hotter, inducing the reactor to create more excess heat, which could make it get hotter yet again. If it thermally runs away, it could keep heating until it melts the nickel, melts the stainless steel container (dangerous), or until some other effect limits the output. The radiation goes as T^4 so that would ultimately also act to stabilize the unit if it is allowed to radiate. This excess heat vs temperature area is not fully explored in the R20 unit so caution is warranted. I would suggest replicating as Mizuno has done first before doing a different experiment. Once you have confirmed Mizuno's excess heat you can do other experiments using the Mizuno excess heat as the new "control" using suitable safety precautions.