| CPC F24H 1/142 (2013.01) [C23C 4/08 (2013.01); C23C 4/131 (2016.01); F24H 1/102 (2013.01); F24H 3/002 (2013.01); F24H 9/1827 (2013.01); F24H 9/1872 (2013.01); H05B 3/48 (2013.01); B32B 15/017 (2013.01); B32B 2250/04 (2013.01); B32B 2307/302 (2013.01); B32B 2307/304 (2013.01); B32B 2311/09 (2013.01); B32B 2311/24 (2013.01); B32B 2311/30 (2013.01); B32B 2315/08 (2013.01); F24H 2250/02 (2013.01); H05B 2203/013 (2013.01); H05B 2203/017 (2013.01); H05B 2203/021 (2013.01)] | 8 Claims |

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1. A method of making a tube heater for heating a fluid in an interior of the tube heater, comprising:
providing a stainless steel core;
circumferentially printing a resistive layer on the stainless steel core including electrically insulating the resistive layer with first and second glass layers, one of the glass layers having a thermal conductivity of more than 2 W/mK and the other of the glass layers having a thermal conductivity of less than or equal to 0.5 W/mK;
dimpling an inner surface of the stainless steel core; and
providing and sealing inside pluralities of balls in an interior of the stainless steel core.
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