Viscosity of helium

Values for the viscosity of helium were calculated from the following equation given in Ref.l ... 

Hydrazine has been studied extensively for use in monopropellant thrusters for space flights of long duration. Thrusters are used or altitude control of communication satellites. Here the decomposition of hydrazine over a packed bed of alumina-supported iridium catalyst is of interest. " In a proposed study, a 2% hydrazine in 98% helium mixture is to be passed over a packed bed of cylindrical particles 0.25 cm in diameter and 0.5 cm in length at a gas-phase velocity of 15m/s and a temperature of 750 K. The kinematic viscosity of helium at this temperature is 4.5 X 10 nF/s. The hydrazine decomposition reaction is believed to be externally mass transfer-limited under these conditions. If the packed bed is 0.05 m in length, what conversion can be expected Assume isothermal operation. 

In spite of this ordered structure, the mobiUty is high and abnormal in character. The viscosity of helium II is low and the viscous flow is independent of the pressure gradient under which it takes place. The substance cannot be confined in a vessel in the ordinary way but flows in the surface films with a facility unlike that shown... 

Viscous flux of helium in a capillary capillary having a radius 0.1 pm and a length of 1 cm. Helium gas is flowing from one end of the capillary of pressure 5000 Torr to the other end of 4000 Torr. Calculate the viscous flux at 298 K. The viscosity of helium at 298K is 1.97 x 10" g/cm/sec. 

Calculate the viscous flux of helium through a packed column containing particle of 1 i in size at 298K. The length of the column is 1 cm, and the pressures at two ends of the column are 500 and 10 Torr, respectively. The bed porosity is 0.34, and the viscosity of helium at 298K is 1.97 X 10 g/cm/sec. 

It is known, that viscosity of liquid is in a direct dependence upon the diffusion coefficient. If the molecules of helium 2 were capable to diffuse (and, therefore, to evaporate), the viscosity of helium 2 could not be equal to zero it means that superfluidity could not exist. 

The viscosity of helium increases with temperature as Consequently, as the temperature of the... 

For a tempCTature of 293 K and a pressure of 1.00 atm, calculate the viscosities of helium gas and of carhon dioxide gas Irom the hard-sphere diameters. Explain why the values compare as they do. 

While use of the close clearance principle is practical in hydrogen pump design, application of it in a high-pressure helium pump is out of the question because of the extremely low viscosity of helium (0.0015 cp) and the relatively high cost of this fluid. A substantial amount of blow-by makes venting of the suction reservoir inevitable in most cases. 

Seven isotopes of helium are known Liquid helium (He4) exists in two forms He41 and He411, with a sharp transition point at 2.174K. He41 (above this temperature) is a normal liquid, but He411 (below it) is unlike any other known substance. It expands on cooling its conductivity for heat is enormous and neither its heat conduction nor viscosity obeys normal rules. 

Figure 4. Graph of Helium Viscosity against Temperature...

The fluidizing gas is usually methane, helium, or another non-reactive gas. Factors to consider to obtain proper fluidization are the density and size of the particles to be coated, and the velocity, density, and viscosity of the gases.If the velocity is too low, the particles will fall into the gas inlet if it is too high, they... 

The viscosity of the carrier gas determines the column pressure drop for a given velocity. For hydrogen, helium, and nitrogen it can be approximated by equations (1.53 to 1.55) in the temperature range of interest for gas [Pg.545]

Figure 2.2—Optimum linear velocity and viscosity of carrier gas. The optimal mean linear velocities of the various carrier gases are dependent on the diameter of the column. The use of hydrogen as a carrier gas allows a faster separation than the use of helium while giving some flexibility in terms of the flow rate (which can be calculated or measured). This is why the temperature program mode is used. The significant increase in viscosity with temperature can be seen for gases. In addition, the sensitivity of detection depends on the type of carrier gas used.

Cellulose Acetates. Fused silica and polypropylene capillaries have been coated with 1% (w/v) solution of CD A in acetone, pushing the coating solution out with a stream of helium, and drying for 30 min with helium. The coating thickness depends on the viscosity of the coating solution and the speed with which the solution is expelled from the capillary. Excellent separations of basic proteins, with efficiencies up to 1 million plates/m, have... 

Estimate the viscosity and thermal conductivity of helium using the Chapman-Enskog model at 1 atm and 422.2,477.8, and 533.3 K and compare with the experimental values (Welty et al. (1984)) in the table below ... 

The effect of temperature on the viscosity of liquid helium is peculiar. The... 

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