An unsteady helicopter rotor: Fuselage interaction analysis

A computational method was developed to treat unsteady aerodynamic interactions between a helicopter rotor, wake, and fuselage and between the main and tail rotors. An existing lifting line prescribed wake rotor analysis and a source panel fuselage analysis were coupled and modified to predict unsteady fuselage surface pressures and airloads. A prescribed displacement technique is used to position the rotor wake about the fuselage. Either a rigid blade or an aeroelastic blade analysis may be used to establish rotor operating conditions. Sensitivity studies were performed to determine the influence of the wake fuselage geometry on the computation. Results are presented that describe the induced velocities, pressures, and airloads on the fuselage and on the rotor. The ability to treat arbitrary geometries is demonstrated using a simulated helicopter fuselage. The computational results are compared with fuselage surface pressure measurements at several locations. No experimental data was available to validate the primary product of the analysis: the vibratory airloads on the entire fuselage. A main rotor-tail rotor interaction analysis is also described, along with some hover and forward flight

A model to calculate dynamical and steady-state behavior of ice particles in ice slurry storage tank

Storage of ice slurries is advantageous to save energy and to produce a continuous controlled long-time operation of an ice-slurry system. To guarantee homogeneous ice particle fields and to prevent a system of blocking by ice clusters, up-to-present a good mixing of the slurries was proposed. But mixing can lead to twenty percent energy demand of the total energy con-sumption of an ice slurry system, including the production of cold. Therefore, new methods are invented to operate systems without a mixing in the storage tank, but still with a control of the fluid and flow conditions in the piping circuits. The theoretical basis to calculate distributions of ice particle fields, respectively ice concentration distributions in unmixed ice slurry storage tanks with stratifications is given and first numerical simulation results are presented

Particle fields of ice slurries with stratifications and melting

Results on isothermal stratification of ice particles in ice slurry storage tanks are presented. Furthermore - in an extension - the melting of ice particles by heat fluxes across the boundaries of storage vessels is also taken into consideration. A conservation equation for the ice particles, respectively the ice fraction, is then accompanied by a second basic differential equation, the energy conservation equation. It is identical to the continuous properties model and describes the melting phenomena. To obtain numerical results, a generally accepted physical-properties model of ice slurries had to be generalized. Further main results are the ice fraction distributions of stratification processes

A magnetocaloric device, especially a magnetic refrigerator, a heat pump or a power generator

The invention concerns a magnetocaloric device, especially a magnetic refrigerator, a heat pump or a magnetic power conversion machine comprising at least a permanent magnet assembly (4, 11) for generating magnetic flux, a rotating ring (2) coaxially disposed to the permanent magnet assembly, a structure containing magnetocaloric material mounted inside the rotating ring (2) and means for conducting a working fluid through the rotating ring (2). The permanent magnet assembly (4, 11) comprises a set of permanent magnets and at least one insert of highly permeable material (1, 9) attached to the magnet assembly (4, 11) adapted for creating high magnetic flux densities around and inside of the rotating ring (2)

Storage and mixing of ice slurries in tanks

Experimental results on storage and mixing of ten-percent-talin/water ice slurries are presented. For this purpose a system with a storage tank, with a volume of 1000 liters and a mixing device containing three slightly inclined cones, was investigated. In first experiments the angular velocity of the mixing device was varied. The variance of numerous temperatures (measured at different locations with different heights in the tank) yields a suitable measure to quantify the stratification. Above a critical rotation frequency, which is a function of the ice fraction, the entire fluid gets into motion and very good mixing is obtained

Breathing building: A decentralized façade-integrated solar air-conditioning system

A decentralized adaptive solar air conditioning system is presented, which contains usual air-conditioning equipment and a new module, designed with a honeycomb structure, containing phase change material for latent thermal cold and hot energy storage. Heat recovery devices are responsible for higher system efficiency. A low-cost configuration and a multi-function deluxe version are presented,where in the second case a (magnetic) heat pump, a (magnetic) cooling device and an evaporative apparatus are added. Whereas the simple configuration is of medium cost and shows a good energy saving potential, the deluxe version is more expensive, but, on the other hand, is designed to show a higher energy saving potential. It is also expected to yield exquisite indoor hygienic and climatic conditions

PRESSURE DROP AND HEAT TRANSFER IN A CYLINDRICAL HEAT EXCHANGER WITH ICE SLURRY FLOW

In an earlier contribution it was shown that the Continuous-Properties Model (CPM) is an ideal theoretical model to calculate melting of ice slurries. Now with a shock-theoretical approach, it is proven that the CPM - in the limit toward a discontinuous melting - just yields the Stefan problem. This limit corresponds to the case when the additive content in an ice slurry tends toward zero. In heat exchangers the ice fraction of an ice slurry is a decreasing function of the downstream space coordinate. The specific pressure drop R=-dp/dx can differ from the inlet to the outlet by more than a factor ten, because the viscosity and the critical shear stress decrease with increasing temperature. A simple analytical model to calculate the overall pressure drop of a cylindrical heat exchanger (with different boundary conditions) is presented

Visualization of ice slurries and ice slurry flows

Visualization of ice particles in a rectangular cavity and ice slurry flows in a pipe are performed. The form and size of ice particles is investigated by optical microscopy, which permits a statistical evaluation of the geometrical shapes of the ice crystals. The observed particle densities and the size distributions correspond with the theoretically determined ice fractions. A method applied to measure ice slurry velocity fields is based on ultrasound Doppler echography. The velocity profile, determined by the velocity of ice particles, is measured and several features which are related to Bingham flows are observed. With these experimental results, complete rheograms can be constructed

Thermodynamics of moving and melting ice slurries

The heat transport to a talin/water ice slurry in a cylindrical heat exchanger was determined by theory and experiment. The theory based on perturbation analysis is only valid for small heat transfer rates. Direchlet and Neumann boundary conditions are applied to numerically calculate temperature profiles at different distances downstream. For the constant-heat-flux-density Neumann boundary condition, numerical results were compared with measured profiles. For laminar and low-Reynolds-number turbulent flows, heat transfer coefficients are presented as a function of the Hedström number