ABSTRACT
Construction of a Heater ................................. 361 9.3 Construction and Placement of Heaters ................... 368 9.4 Design of Metallic Elements ...................................... 373
9.4.1 Determination of Wire or Strip Size ...................................................... 377
9.5 Nonmetallic Heating Elements .................................. 383 9.5.1 Silicon Carbide Heating Elements.................. 383 9.5.2 MoSi
Heating Elements.................................. 385 9.6 Design Calculations for Nonmetallic
Elements ...................................................................... 387
9.7 Direct Resistance (Conductive) Heating (DRH)........ 401 9.7.1 Principle of DRH .............................................. 401 9.7.2 Design for DRH ................................................ 403 9.7.3 Advantages and Limitations of DRH.............. 405
9.8 Stored Energy Heating (SEH).................................... 408 9.8.1 Principle of Stored Energy Heating................ 409 9.8.2 Practical Heating Circuit................................. 411 9.8.3 Some Peculiarities of SEH............................... 411
9.9 Salt Bath Furnaces ..................................................... 414 9.9.1 Introduction ...................................................... 414 9.9.2 Construction and Working
of Electrode Furnaces....................................... 415 9.9.3 Bath Salts ......................................................... 416 9.9.4 Some Peculiarities of Salt Baths..................... 419 9.9.5 Applications of Salt Baths ............................... 419 9.9.6 Other Bath Furnaces ....................................... 421
When an electric current flows through a material (preferably a good conductor) some energy is dissipated in the form of heat due to the resistance offered by the material. This phenomena offers a good, clean, and easily controllable source of heat, and is used on a very large scale in industrial and domestic heating. The object or work can be heated “indirectly” by exposing it to an electrically heated radiator or heater, or element. Alternatively, the object itself can be used as a resistance or heater in which heat is generated internally. In this chapter we will discuss both modes of electrical resistance heating.
