A transportable combustion air heater comprises a transportable supporting frame, a housing fixed to the frame, a cylindrical combustion chamber arranged in housing, a cylindrical annular thermal exchange channel formed around the combustion chamber, an external heating chamber defining an annular fume channel around the thermal exchange channel, in which one or more transversal guide walls are arranged in the external heating chamber, which guide walls lengthen flow paths of the fumes in the annular fume channel from fume inlet openings to an exhaust fume opening.

In a heat tracing system using heat from a radiant heater to heat a circulating fluid, thermoelectric generation modules are used to generate electricity for powering a circulating pump. Thermoelectric power generation modules are sandwiched between a heat-absorbing plate and a heat sink, and this assembly is positioned with the heat-absorbing plate adjacent to a radiant heater. A conduit loop passes through the heat sink, such that a fluid circulating through the conduit is heated from heat drawn from the heater into the heat sink. Due to the temperature differential between the hot and cold sides of the thermoelectric modules, the modules produce electricity to power the pump circulating the fluid through the conduit loop. Supplementary heat exchanger components may be provided for additional fluid-heating capacity, and thereby increasing the amount of heat available for the heat tracing loop.

A plumbing fixture includes a water passage configured to hold water, a first plate shaped according to a cross section of the water passage and spaced at a first distance from the water passage, and a second plate shaped according to the cross section of the water passage and spaced at a second distance from the water passage. A voltage between the first plate and the second plate is generated based on the water in the water passage.

A system includes a vortex tube. A first thermoelectric terminal is in thermal communication with the first outlet of the vortex tube. A second thermoelectric terminal is in thermal communication with the second outlet of the vortex tube. An electrical circuit is electrically connected to the first thermoelectric terminal and to the second thermoelectric terminal for electrical conduction of Peltier-effect thermoelectric current. The systems and methods described herein can be used to enhance temperature difference generated in a vortex tube, and/or to harvest energy from the temperature difference in a vortex tube.