I.A. Kovalev

Nucleate and film pool boiling heat transfer to saturated liquid helium

Abstract Pool boiling heat transfer from a square copper heating surface to liquid helium has been investigated experimentally. The study includes both nucleate and film boiling regimes, the measurements of maximum and minimum heat fluxes and superheats of the heating wall in the pressure region from 0.445 up to 0.98 P/P c . The results are compared with the available experimental data and correlations.

Forced convection heat transfer to liquid helium I in the nucleate boiling region

Abstract Heat transfer and critical heat fluxes to helium boiling in a 2 mm id copper tube (100 mm long) were measured in the pressure range 1.1–1.5 atm and at mass velocities 18–96 kg m −2 s −1 . Corresponding Reynolds numbers are (1.2–6.2) × 10 4 . Experimentally obtained heat transfer coefficients show satisfactory agreement with those calculated according to the Kutateladze equation but with less pronounced pressure dependence. It was found that in the boiling region developed quality did not influence the heat transfer coefficient. An expression was obtained, which describes with ±10% error, the dependence of critical heat flux on mass flow rate in the pressure range 1.1–1.5 atm and mass quality 0.33–0.6.

Force-cooled superconducting systems

Abstract Force-cooled superconducting systems (f c s s) are compared with traditional ‘pool’ systems. A model is proposed to determine the stability criteria for current in f c s s and some results of the analysis of this model are presented. A force-cooled superconducting coil and the apparatus to test the coil, built in IV Kurchatov Atomic Energy Institute during 1968, are described. The results of the tests on the coil are also presented.

Device for measuring pressure drop and heat transfer in two-phase helium flow☆

Abstract A device for studying hydrodynamics and heat transfer in helium flow (helium being in two-phase liquid, and supercritical states) is described. Preliminary data about pressure drop and heat transfer in two-phase helium flow are presented. The tube used was about 0.45 mm i d and about 1 m long. The mass flow in the tests ranged from 1·5 × 10−2 gls, heat flux from 0·02 to 0·5 W/cm2 and quality x (mass vapour fraction) ranged from 0 to 100%. The dependence of Δp/[xΔpv + (1 - x)Δp1] on x is found to be a convenient (in the opinion of the authors) form of presentation of experimental two-phase pressure drop data.

Concerning the possibility of compensating heat inputs into liquid helium

Abstract The possibility of the partial compensation of heat influxes into liquid helium using return streams of evaporated helium, say, in a simple Joule-Thomson cycle is discussed. The elevated pressure helium flow can be cooled to sufficiently low temperatures because of the larger quantity of return flow. Unlike liquefiers and refrigerators whose net refrigeration capacity is correspondingly greater than or equal to the heat load, the ‘refrigeration capacity’ of the devices under consideration is less than the heat load. Such devices one can consider as ‘compensators’. It is shown that the pressure range needed is of the order of several atmospheres. Some basic design relationships are derived. The experiments carried out confirmed the possibility of the compensation of a considerable part of heat influxes. The experimental arrangement as well as the main experimental results are briefly described. Some possible applications of compensators are discussed.