Method of heating liquid

A method for heating a liquid comprising the steps of:

• (1) placing in the liquid a heating article comprising:
• (a) a water-impermeable, heat conductive housing;
• (b) within the housing, a heating element sufficiently flexible to conform to the shape of the housing and capable of providing from about 1 to about 10 watts per square inch of surface area of the heating element;
• and
• (c) coupling means for maintaining the heating element thermally coupled to and in intimate engagement with the interior of the housing;
• and
• (2) connecting the heating article to a source of electrical power so that heat is transmitted from the heating element through the housing to the liquid.

A method for heating a liquid comprising the steps of:

• (1) placing in the liquid a heating article comprising:
• (a) a water impermeable, heat conduction housing fabricated from a meltable material having a notched Izod impact strength of at least about 0.5 ft-lbs/in.;
• (b) within the housing, a flexible heating element capable of providing from about 1 to about 10 watts per square inch of surface area of the heating element;
• and
• (c) a circuit protection element comprising at least two electrodes and a PTC element composed of a PTC composition for preventing the heating element from raising the temperature of the housing to a temperature at which it softens or melts;
• and
• (2) connecting the heating article to a source of electrical power so that heat is transferred from the heating element through the housing to the liquid.

A method for heating a liquid comprising the steps of:

• (1) placing in the liquid a heater comprising:
• (a) a water-impermeable, heat conductive, electrically insulating, closed housing comprising a hollow heating section for immersion in water, walls of the heating section having a notched Izod impact strength of at least about 0.5 ft-lbs/in. and a heat distortion temperature at 264 psi of at least about 350.degree. F.;
• (b) a distributed heating element within the heating section of the housing, the heating element being capable of providing from about 1 to about 10 watts per square inch of surface area and being sufficiently flexible to conform to the interior surface of the heating section;
• (c) coupling means for maintaining the heating element thermally coupled with the internal surface of the heating section walls;
• and
• (d) temperature limiting means for preventing the heating element from heating the housing to a temperature at which the housing melts or softens;
• and
• (2) connecting the heater to a source of electrical power so that heat is transferred from the heating element through the housing to the liquid.

A method for heating water in an aquarium comprising the steps of:

• (1) placing in the water in the aquarium an aquarium heater comprising:
• (a) a water-impermeable, heat-conductive, electrically insulating, closed housing comprising a hollow, thin, elongated, wedge-shaped heating section for immersion in water in an aquarium, the heating section walls having a heat transfer coefficient of at least about 2 BTU-inches per hour-square foot-.degree.F., a notched Izod impact strength of at least about 0.5 ft-lbs/in., and a heat distortion temperature at 264 psi of at least about 350.degree. F.;
• (b) a flexible, distributed heating element within the heating section of the housing, the heating element being insulated from the water and being capable of providing from about 3 to about 7 watts per square inch of surface area;
• (c) a wedge-shaped support for maintaining the heating element in intimate engagement with the internal surface of both of the wider side walls;
• and
• (d) a circuit protection element comprising at least two electrodes and a PTC element composed of a PTC composition, the temperature limiting device being selectively located in the heating section of the housing for preventing the heating element from heating the housing to a temperature at which the housing melts or softens;
• and
• (2) connecting the heater to a source of electrical power so that heat is transferred from the heating element through the housing to the water.

A method for heating a liquid comprising the steps of:

• (1) placing in the liquid a heating article comprising:
• (a) a water-impermeable, electrically insulating housing comprising a hollow heating section for immersion in the liquid, the walls of the heating section being from 0.05 to 0.2 inches thick and being composed of a material having a notched Izod impact strength of at least 0.5 ft-lbs/in., a heat distortion temperature at 264 psi of at least 350.degree. F., and a thermal conductivity of at least 2 BTU-inches per hour-square foot-.degree.F.;
• (b) a flexible distributed heating element within the heating section of the housing, the heating element being capable of providing from about 1 to about 10 watts per square inch of surface area and conforming to the interior surface of the heating section;
• (c) a support member for maintaining the heating element in contact with the internal surface of the heating section walls;
• and
• (d) an adjustable thermostat for regulating the heating element;
• and
• (2) connecting the heating article to a source of electrical power.