Study of jet pumps for circulating a helium two-phase mixture

The operation of a jet pump using a helium, two-phase mixture has been studied. It is shown that for the two-phase region, the relations obtained from the momentum equation are valid only up to the onset of limiting modes, ie until the stream velocity achieves the velocity of sound in any section of the mixing chamber of the jet pump. The experimentally proved method of calculation of the limiting modes is presented in which the velocity of sound in a two-phase stream is determined by thermodynamic theory.     

Study of a liquid helium jet pump for circulating refrigeration systems

A basic diagram of the refrigeration system, in which liquid helium is circulated by means of a jet pump, is described. The equations have been derived to design jet devices which operate with liquid helium.In the experimental setup with a jet pump the flow rate of liquid was 5 to 10 times larger than that of compressed gas in a direct stream of the refrigerator. After pumping the pressure was equal to (0.15–0.40) × 10⁵Nm^?2. A circulating stream of liquid helium at supercritical pressure, due to the heat load corresponding to the refrigerator capacity, was heated to 0.15–0.25 K.The results of our studies permit one to determine circulation loop parameters and main geometric dimensions of the jet pump.     

Liquid helium pumps for in-orbit transfer

Both mechanical and fountain-effect pumps are being considered for use in the in-orbit resupply of superfluid helium to a number of scientific instrument systems. This Paper presents a review of the operating characteristics of these pumps. Particular emphasis will be given to the different methods of evaluating the efficiency of these pumps and their effectiveness in a transfer system.     

Influence of the two-phase helium flux structure on heat transfer dynamics

It is established as a result of an experimental investigation that the quantitative and qualitative characteristics of nonstationary heat transfer depend substantially on the two-phase helium flux structure. A simple working model that permits estimation of the influence of the expended mass vapor-content and density of the heat flux on the dynamics of the process for a homogenized phase distribution (bubble and emulsion flow modes) is proposed to describe nonstationary film boiling. The fundamental heat transfer singularities under conditions of a dispersely annular flux structure are noted.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 6, pp. 885–892, June, 1990.     

Heat transfer to two-phase flows of helium and nitrogen in vertical channels

Equations are presented for calculation of heat transfer in two-phase convection and well-developed bubble boiling of helium and nitrogen in vertical channels.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 6, pp. 885–892, December, 1986.     

Fountain effect pump phenomena for liquid helium transfer: thermodynamic system studies

Special constraints are imposed on liquid helium transfer in space relying on the fountain effect (thermomechanical effect) for the movement of liquid He II below the lambda point. The present Paper considers thermodynamic pump system options and compares performance figures with requirements of different system selections.     

Dispersion of a heavy admixture in a two-phase jet

The article presents experimental data on the distribution of finely-divided powder in the cross sections of a turbulent axisymmetric jet and a qualitative analysis of the experimental data, and the possibility of their generalization is shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 3, pp. 538–541, March, 1970.     

Experimental study of a submerged supersonic two-phase jet

An optical-laser method was used to measure the size and concentration of liquid drops in a supersonic gas-drop jet.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 3, pp. 379–383, September, 1988.     

Hydrodynamic characteristics of a horizontal channel with the motion of a two-phase helium flow

Experimental data is presented on the pressure drop in the motion of a two-phase helium flow in a horizontal pipe under adiabatic conditions and with a supply of heat.     

Modeling of a horizontal circulation open loop in two-phase helium

In the process of the cryogenic cooling system design of the superconducting magnet of the R³B spectrometer, heat and mass transfer in a two-phase He I natural circulation loop with a horizontal heated section has been investigated experimentally. The experiments were conducted on a 2 m high experimental loop with a copper tube of 10 mm inner diameter uniformly heated over a length of 4 m. All data were obtained near atmospheric pressure. Evolution of the mass flow rates as a function of heat flux in steady state condition are presented and compared to a numerical model that have been developed to assist the design of such a cooling scheme. The model is based on a one-dimensional equations system, which includes mass, momentum and energy balances. It is based on the homogeneous model with a specific friction coefficient for the horizontal heated section. The model reproduces with an acceptable accuracy the experimental results and now serves as a tool for the design.     

Centrifugal pump for superfluid helium

This Paper summarizes and correlates the liquid helium pump data obtained previously in two separate test programs. In normal helium the second set of data shows a large performance improvement over the first set as a result of changes in measurement methods and in the pump itself. Peak pump efficiencies of 46% were measured. The pump appeared to perform approximately the same in He II as in He I; however, the He II data are not adequate for system design or analyses. Therefore, a new pump test program is planned to test the improved version of the pump in an apparatus designed specifically for He II.     

Liquid pool helium cryopump

A liquid pool helium cryopump, without liquid nitrogen bath, is described. The details of its construction and experimental results are presented.     

Design and construction of a pump for liquid helium

A pump constructed to circulate liquid helium in superconducting magnets wound with hollow conductors, is described. The pump is a three-cylinder reciprocating engine which, when operating at its nominal rating of 60 turns per minute, circulates a flow of $\text{? 100}\text{g s}{}^{\mathrm{?1}}$ of liquid helium with a pressure drop of a few tenths of atmosphere.     

Mass transfer in a jet device

The process of mass transfer in a jet device has been investigated by the evaporation of water. Methods of calculating the interface formed by gas bubbles and measuring the mass-transfer coefficient have been developed. The experimental and calculated mass-transfer coefficients have been compared. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 84–88, November–December, 2005.     

Non-stationary helium heat transfer

This Paper presents the results of an experimental investigation of heat transfer to helium in stationary conditions, in conditions of increase and decrease of heat power at various rates and with pulse heating. Heat transfer both from a free surface and in a coaxial gap of 0.5 mm was studied. The experiments were carried out within the range of liquid saturation temperatures from 1.94 to 4.23 K. The values of the heat loads in a pulse were ≈1.5 – 15 times the steady-state value of the critical heat flux for helium nucleate boiling. It has been shown that transient thermal processes may have higher heat transfer coefficients compared with steady-state conditions. The most pronounced effect is observed under pulse heating conditions.     

Downward two-phase flow applications for a non-conventional heat pump

A non-conventional heat pump working by a difference in density between two branches of a hydraulic vertical loop has been described. This system called thermogravimetric heat pump, TGHP, operates with a non-conventional regenerative thermodynamic cycle which remarkably improves COP values. The lower density in the ‘downward branch’ is obtained by a liquid–vapour two-phase flow. Performances and main geometrical characteristic trends, such as plant height Z and two-phase column diameter D_T–PD have been drawn, varying the minimum cycle temperature between 15 and 25 °C and the user temperature, T_max, in the range 60–70 °C. The carrier fluid is demineralized water; according to the peculiar working fluid—PP 50, HFC 134a and HFC 338cca—different solutions can be obtained, such as for 10–12 storey buildings or for skyscrapers. Yet, the results obtained with HFC 338cca must be accepted with some cautions while waiting for a better characterisation of such fluid. Chemical compatibility, thermal stability, environmental impact have been also taken into account in the choice of the operating couple, carrier fluid—working fluid. While the thermodynamic conversion process is non-conventional, the TGHP can be assembled by standardised technology. The compressor of a conventional plant is here replaced by a feeding pump and COP values obtained through a regenerative TGHP are globally larger than those of a common heat pump.     

Interaction of a two-phase jet with a solid body with generation of a “Chaos” of particles

A simple physicomathematical model of interaction of an axisymmetrical supersonic monodispersed jet with a solid body is proposed. The interaction leads to a rise of the fractions of reflected spinning particles and a “gas” of chaotized particles. This “gas” has its inherent pressure and diffusion coefficient. Numerical solutions of the corresponding system of equations are obtained in a wide range of the mass fractions of the particles in the mixing chamber. The model developed enables the shielding effect of reflected and chaotized particles to be estimated. In particular, their effect on heat transfer between the two-phase jet and the streamlined body can be estimated.     

Investigation of a rotating liquid helium transfer coupling

A bayonet coupling of a stationary transfer tube with a liquid helium, rotating dewar, horizontal neck has been tested. A relation between the heat leak to liquid He in the coupling and the dewar rotation speed at different bayonet lengths has been derived.     

An analytical study of two-phase helium flow within a radial rotating duct

A study was made of the behaviour of separated two-phase helium flow within a radial rotating duct. The liquid film thickness, phase velocities, heat-exchange coefficients, pressure and temperature differences were evaluated. The plots obtained for helium flow in thermodynamic equilibrium are used to calculate the radius dependence of pressure and quality at a given rotational frequency and inlet duct conditions. The equilibrium pressure model is presented which describes pressures not too close to the critical values.