I think the inside-out design (see the picture) of reactor should be better in terms of heat exchange and temperature control.
I would like to clarify three points about the suggested inside-out design of the reactor.
1. The inside-out design allows to deliver heat to “a consumer” better than the tested now design (used in the replications by MFMP members, Parchomov, Denis Vasilenko) exactly because of the principle of the inverted scheme. Why? It is because of the temperature gradient from heater inside to outside reactor tubes. The heater placed inside will maintain the temperature and LEN reaction (at certain temperature because of heater) in the layer of fuel more close to heater and the outer layer of fuel can have lower temperature, because of delivering heat to the “consumer”, without the danger to shut down the LENR in the whole fuel completely, or to allow LENR to run away. From my point of view the temperature gradient of the fuel from inside to outside is a key for stable LENR and heat production.
2. Sealing of the inside-out designed reactor at both ends is not difficult and not different from the tested design. Instead of roads with cement in the already tested design, the rings (as it was written, between the outer and inner reactor tubes) with cement can be used with the same efficiency as for the tested design.
3.1. Not only temperature but also pulsed magnetic field can be used to maintain the LENR by using the coil with appropriate electric current on the outside tube of the reactor.