Various Modes Of Heat Transfer Research Articles

Some characteristics of transferred-Arc plasmas

Although the theoretical foundations of the characteristics of transferred arcs were established more than three decades ago, the design of reator systems based on this method of plasma are generation is still in an early stage of development. Although deceptively simple in concept, attempts to use transferred arcs im practical applications at scales of arc length and power somewhat larger than those previously studied in the laboratory soon revealed that considerably more information was required on the arc's unique properties before a sound reactor design could be carried out. This was principally due to the much higher temperature levels (up to 20,000 K) with consequent much higher radiative power achieved in this type of arc, as well as the fluid mechanical effects of the high-velocity plasma gas flowing in the latter. These, in turn, had profound effects on the various modes of heat transfer occurring in the system, on the stability of the arc, on the injection of the material to be treated, and on the overall efficiency of energy utilization in the whole system. The objective of this paper is to summarize the experimental evidence concerning transforred arc characteristics which have been obtained by the author and his colleageus during recent years.

HEAT TRANSFER STUDIES ON A ROCKET NOZZLE FOR NAVAL APPLICATION

ABSTRACTHeat transfer results are presented here for a rocket nozzle that uses aluminized solid propellant. The Solid Performance Computer Program (SPP) was employed to calculate the two‐dimensional, two‐phase flow properties inside the nozzle. Utilizing the properties of particle phase obtained from this program, calculations were made for the heat flux due to particle impingement. Predictions are also presented for convective and radiative heat transfer along the nozzle surface. A comparison was made to assess the magnitudes of various modes of heat transfer. The methodology and results presented in this paper should provide useful data to designers of new rocket nozzles and should aid studies to improve the design of existing nozzles.

Heat Transfer R & D in Support of CANDU Reactors

The paper reviews various types of thermalhydraulic models used in computational analysis in support of reactor design, and concentrates on particular areas of research and development, fundamental to defining accurately the various modes of heat transfer upon which reactor operation depends.

Measurement of anode falls and anode heat transfer in atmospheric pressure high intensity arcs

Electric probe measurements have been performed at and close to a plane, water-cooled anode surface in atmospheric pressure, high intensity argon arcs for different arc configurations which in turn, result in two distinctly different anode arc roots (diffuse and constricted). An adjustable fine wire probe penetrating through a small hole in the center of a flat anode allows for potential and electron temperature measurements in the anode boundary layer. For the parameter range covered by this investigation (100 A≤I≤250 A) the results reveal negative anode falls ranging from approximately −2.1 to −1.4 V. Electron temperatures at the anode surface range from 8800 to 9800 K. Calorimetric energy balances from which the contributions of the various modes of heat transfer to the anode may be derived, indicate the importance of convective heat transfer to the anode. The results of the calorimetric studies as well as of the anode fall measurements are consistent with a revised anode heat transfer model which takes negative anode falls into account.

Bubble induced heat transfer in two phase gas-liquid flow

The influence of gas bubbles on heat transfer in two phase gas-liquid systems has been investigated. Platinum wires have been used as heat-transfer probes and the two phase flow has been simulated by generating a single continuous stream of discrete gas bubbles into a stationary liquid. The contribution of various modes of heat transfer has been determined. It has been found that transient conduction into the liquid is the predominant mode of the bubble induced heat transfer and is responsible for about 75 per cent of heat transfer. Convection contributes the remainder. A theoretical model of the bubble induced heat transfer based on the surface renewal and penetration theory has been developed.

Flame Propagation Measurements and Energy Feedback Analysis for Burning Cylinders

Abstract Flame spreading velocity measurements were made using PMMA cylinders as fuel rods. The diameter of the rods varied from 1½10; to 1½2 inch, and burning was observed at angles of orientation from θ = −90° (vertically downward burning) θ = +40°. The length of the pyrolysis zone was measured and used to calculate an average surface regression rate. For the axisymmetric case of vertically downward burning, surface temperatures were measured in the pyrolysis zone and in front of the flame; internal temperatures were measured in front or the flame. The measured temperatures were used to evaluate a number of energy balances. As a result, values were obtained for the energy feedback from the flame to the fuel by the various modes of heat transfer.

Heat Transfer in a Gas-Fired Furnace

Abstract The general problem of heat transfer in a gas-fired furnace is examined. A method of analysis is introduced for determining the contributions of the various modes of heat transfer. A particular furnace, gas-fired with non-luminous flames, is investigated in the temperature range of 1750 to 2110 F. The results indicate that approximately 80 per cent of the heat is transferred by radiation from the furnace walls to the charge being heated and the remainder by gas convection and gas radiation.