Accession Number : AD0658373

Title :   HEAT TRANSFER IN ROTATED ARCS WITH WATER-COOLED ELECTRODES,

Corporate Author : JOHNS HOPKINS UNIV SILVER SPRING MD APPLIED PHYSICS LAB

Personal Author(s) : Raezer,Spencer D.

Report Date : 05 DEC 1961

Pagination or Media Count : 19

Abstract : In the range of Q (1,000,000 watts/sq cm and higher) for the operation of wind tunnel heaters, it is doubtful that the arc can be rotated with sufficient rapidity to eliminate surface melting and vaporization. The problem encountered differs from the more commonly met steady-state heating of a water-cooled wall in two basic respects: (1) the magnitude of the heat flux into the wall in the range of interest greatly exceeds that which can be supported in practice by the wall to coolant interface, and (2) heating is extremely short in duration and periodic. This means that whereas normally in the case of steady-state heating of a well-cooled wall the surface temperature can be kept below melting by making the wall appropriately thin, in our case thinning the wall can have the effect of causing its destruction by increasing the local flux to the coolant over that which can be safely transferred without film boiling. As the flux to the wall is increased, the wall should be thickened since it acts as a kind of 'capacitive-resistive' buffer-zone between the arc and coolant as is evident from the analysis. However, it is also necessary to increase the arc path length (duration of the cooling time tau) to keep the average wall temperature down. Because of this and because of the loss of wall material resulting from erosion, thick electrode walls and long arc path lengths are suggested. However, long path length means larger electrodes and a larger pressure vessel to contain them unless a means can be found for causing the arc to wander over a more devious path during a period to utilize the electrode area more effectively. (Author)

Descriptors :   (*HEAT TRANSFER, *ELECTRIC ARCS), (*ARC HEATERS, WIND TUNNELS), ROTATION, COOLING, WATER, ELECTRODES, PLASMAS(PHYSICS), EROSION, HEATING, SURFACES

Subject Categories : Air Condition, Heating, Lighting & Ventilating
      Test Facilities, Equipment and Methods
      Electricity and Magnetism
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE