Heat Transfer In He Research Articles

Transient thermal and hydrodynamic processes in superfluid helium

The experimentally observed regimes of transient heat transfer in He II are described and classified. A variety of results is shown to agree well with the concept of superfluid turbulence.

NUMERICAL SOLUTION OF FORCED CONVECTION HEAT TRANSFER IN He II

A theoretical investigation of one-dimensional forced convection heat transfer in He II is conducted. The problem of interest involves a flow tube containing He II, which is heated at its midpoint along its length. Two modes of heating are analyzed: step function and square pulse. The one-dimensional He II energy equation is used to find the temperature distribution along the tube for both steady-state and transient situations. For the steady-state case, a numerical integration routine is used to obtain a solution, whereas for the solution of the transient case, a finite-difference scheme is developed. The numerical temperature profiles are then shown to compare well with the results of an experiment.

Two dimensional transient heat transfer in He II

A comparison is presented of transient heat flow in He II as measured experimentally and as predicted by analysis based on the Gorter-Mellink equation. The geometry is that envisioned for the He II cooling of a SMES (superconducting magnetic energy storage) system, namely, an annular layer of He II in direct contact with one layer of a solenoid and extending the full height of the coil. A normal zone over a fraction of a turn provides for two-dimensional heat flow in the annular layer of the He II. The comparison is given for both adiabatic and isothermal boundary conditions at the end of the channel. Good agreement between the analysis and the experimental data is found, verifying the usefulness of the analysis for large-scale systems. In addition, discrepancies between the analysis and data provide insight into the stability process of the He II cooled superconductor. >

Channel heat transfer in He II — steady state orientation dependence

Abstract Heat transfer measurements of a channel configuration containing He II are reported. The configuration is a rectangular cross-section channel heated uniformly over its length and open at both ends so that natural circulation can occur. The gap dimension and the angular orientation of the channel are variable. Enhanced heat transfer occurs in the lower portion were all obtained at a nominal bath temperature of 1.9 K and atmospheric pressure (p ≈1 bar † ).

Heat transfer in He I for industrially manufactured aluminium plate heat exchangers

Abstract The heat transfer characteristics in boiling helium for commercially available aluminium plate heat exchangers, with and without fins, are given. In nucleate boiling both surfaces present the same heat transfer characteristics. For film boiling, the presence of fins improves heat transfer. It was also verified that for surfaces without fins, the peak nucleate boiling flux follows a Kutateladze law.

Correlation of time dependent recovery from film boiling heat transfer in He II

A correlation is presented that describes the behaviour of time dependent recovery from film boiling in He II. In a one dimensional heat transfer experiment, the recovery time from the film boiling once heat generation stops is observed to be a function of the energy applied to the heater during film boiling. This correlation has a power law dependence which can be physically understood in terms of heat capacity of the heat transfer sample and the film boiling heat transfer coefficient. A direct comparison of experimental data with the analysis is achieved by adjusting the value of the transient film boiling heat transfer coefficient. Data can be predicted to within 20% for recovery under SVP conditions. The results are somewhat less certain for data taken in subcooled He II.

Stabilization of large superconducting magnets in superfluid helium

Stability of large superconducting magnets cooled with superfluid helium (He II) is examined. Impetus for this research is the Wisconsin Superconductive Energy Storage magnet system, which proposes to be operated at 1.8 K. A survey of steady state heat transfer in He II is presented in the context of magnet stability. In addition, new results from an experiment to study the transient response of He II show substantially better heat transfer than that of normal helium (He I). For example, a step-function application of heat flux at a rate of 2 W/cm2can be absorbed by the helium for about five seconds before film boiling begins. This time delay is caused by the required temperature rise of the He II adjacent to the hot spot. A comparison between the enthalpy rise in the helium and the applied energy shows a close correlation. These new results are discussed in terms of superconducting magnet stability.