Small diameter low watt density immersion heating element

• US 6,744,978 B2
• Filed: 07/19/2001
• Issued: 06/01/2004
• Est. Priority Date: 01/08/2001
• Status: Expired due to Term

• Current Assignee: Watlow Polymer Technologies
• Original Assignee: Watlow Polymer Technologies
• Inventors: VonArx, Theodore, Tweedy, Clifford D.
• Primary Examiner(s): Campbell, Thor
• Application Number:
  US09/908,863
• Publication Number:
  US 20020127006A1
• Time in Patent Office: 1,048 Days
• Field of Search: 392/465, 392/466, 392/451, 392/459, 392/485, 392/487, 219/481, 219/490, 219/494
• US Class Current: 392/451
• CPC Class Codes: F24H 1/102 with resistance
• CPC Class Codes: H05B 3/54 flexible

Abstract

The present invention provides immersion heating elements, water heaters and methods for their fabrication and use. In the first embodiment of this invention, a resistance heating element is provided which includes a resistance heating material and an electrically insulating, substantially water impervious sheath disposed over the resistance heating material to form an active element portion having an envelope of about 50 in³, a total wattage of at least 1000 W, and a watt density of no greater than 60 W/in². Such an element has been demonstrated to substantially reduce scale reduction in water containing calcium, calcium carbonate, or both in solution.

Claims

1. A method of heating a quantity of water within a storage container, comprising:

providing a storage container having a storage capacity of at least one gallon, said storage container containing a substantially renewable supply of water, said storage container having a water inlet and a water outlet;

said water containing calcium, calcium carbonate, or both, in solution in a sufficient concentration to form a scale deposit during the heating of said quantity of water;

said storage container also including an electrical resistance immersion heating element disposed therein;

said immersion heating element including a resistance heating material disposed within an electrically insulating, substantially water impervious sheath;

self limiting an upper temperature of said immersion heating element due to scale deposit induced overheating thereof, by said resistance heating material having, a watt density of no greater than about 60 W/in², and an overall wattage rating of at least about 1000 W;

said immersion heating element having a capability of fitting within an envelope of no greater than about 50 in³; and

electrically activating said immersion heating element to produce power for heating said water above ambient temperature, and self-limiting the upper temperature of said resistance heating material as induced by formation of said scale deposit.

2. The method of claim 1 wherein said resistance heating material comprises a spiral or coil which permits the free circulation of water over its surface.

3. The method of claim 1 wherein said resistance heating material has a diameter of less than about 0.25 inches.

4. The method of claim 1 wherein said electrically activating step activates said immersion heating element to produce about 2500-4500 W.

5. The method of claim 1 wherein said immersion heating element substantially reduces the growth of said scale in said storage tank, generating at least 10 wt% less scale than a metal tubular clement having a 0.315 in. diameter metal sheath and an equivalent envelope.

6. The method of claim 5 wherein said immersion heating element comprises a polymeric-coated wire.

7. The method of claim 1 wherein said immersion heating element is capable of fitting within an envelope of no greater than about 30 in.³.

8. The method of claim 1 wherein said resistance heating material comprises a watt density of about 10-40 W/in.².

9. The method of claim 1 wherein said immersion heating element comprises at least a pair of layered coils made from a coated resistance wire.

10. In combination, a storage container capable of holding at least one gallon and an electrical resistance immersion heating element for heating water, comprising:

a storage container having contained therein a substantially renewable supply of water, said water containing calcium, calcium carbonate, or both, in a sufficient concentration to form a scale deposit during the heating of said water;

an electrical resistance immersion heating element mounted through a wall of said storage container, said electrical resistance immersion heating element including a resistance heating material disposed within an electrically insulating, substantially water impervious sheath to form an active element portion;

said active element portion having a self limiting upper temperature due to scale deposit induced overheating thereof, by said resistance heating material having a cross-sectional dimension of no greater than about 0.25 inches (6.35 mm); and

having a watt density of no greater than about 60 W/in², while providing a total wattage rating of at least about 2500-4500 W; and

said active element portion being capable of fitting within an envelope of less than about 50 in³.

11. The combination of claim 10 wherein said active element portion comprises a watt density of no greater than about 10-40 W/in².

12. The combination of claim 10 wherein said active element portion comprises a Ni—

Cr alloy wire coated with a fluorocarbon-based polymer.

13. The combination of claim 10 wherein said active element portion is capable of fitting within an envelope of less than 30 in³, and is capable of insertion through a sidewall opening in said storage container of about 1.0-1.5 inches in diameter.

14. The combination of claim 10 wherein said immersion heating element further comprises temperature control means for controlling electrical current through said element.

15. A resistance heating clement comprising:

a resistance heating material;

an electrically insulating, substantially water impervious sheath disposed over said resistance heating material to form an active element portion;

a pair of terminal ends extending from said resistance heating material for connecting said resistance heating element to an external source of electrical power;

said active element portion defining an envelope having an envelope length less than 30 in. and a cross-sectional envelope dimension of less than 1.5 in.;

said active element portion capable of generating a total wattage of at least about 1000 W and having a self limiting upper temperature due to scale deposit induced overheating thereof, by said resistance heating material having a watt density of no greater than 60 W/in²; and

said active element portion by having said self limiting upper temperature being capable of substantially reducing scale production in water containing calcium, calcium carbonate, or both.

16. The resistance heating element of claim 15 wherein said active element portion comprises a polymeric-coated wire or a tubular configuration.

17. The heating element of claim 16 wherein said polymeric-coated wire or tubular configuration has an outer diameter of less than about 0.25 in.

18. The heating element of claim 16 wherein said self limiting upper temperature is about 400°

F.

19. The heating element of claim 15 wherein said active element portion has a watt density of 10-40 watts/in².

20. The heating element of claim 15 wherein said active element portion comprises a resistance heating wire coated with a fluorocarbon-based polymer and having a watt density of no greater than about 20-35 watts/in² and an outer diameter of no greater than about 0.125 in.

21. A water heater comprising:

a storage container wall comprising a thermally conductive, water impervious polymeric material;

an electrical resistance heating element disposed within said storage container wall, said electrical resistance heating element including a resistance heating material which is electrically insulated from the contents of said storage container;

said electrical resistance heating element having a self limiting upper temperature due to scale deposit induced overheating thereof, by said resistance heating material having a watt density of no greater than about 60 W/in² while providing a total wattage rating of at least about 1,000 watts; and

said electrical resistance heating element by having said self limiting upper temperature being capable of substantially reducing the growth of scale in said storage container.