直接火管锅炉 direct fire tube boiler

非直接火蒸汽锅炉 Unfired steam boiler

直接火焰炉 direct firing furnace

直火油加热炉 direct fired oil furnace

直焰式火管锅炉 direct tube boiler

直火式熔炉 [炉窑] direct-fired furnace

直接火加热炉 direct fired heater