Engineering topics

Saiyed, N. H.

Publications and source records attributed to Saiyed, N. H..

3 records

NASA NTRS1992

Description of liquid nitrogen experimental test facility

The Liquid Nitrogen Test Facility is a unique test facility for ground-based liquid nitrogen experimentation. The test rig consists of an insulated tank of approximately 12.5 cubic ft in volume, which is supplied with liquid nitrogen from a 300 gal dewar via a vacuum jacketed piping system. The test tank is fitted with pressure and temperature measuring instrumentation, and with two view ports which allow visual observation of test conditions. To demonstrate the capabilities of the facility, the initial test program is briefly described. The objective of the test program is to measure the condensation rate by injecting liquid nitrogen as a subcooled spray into the ullage of a tank 50 percent full of liquid nitrogen at saturated conditions. The condensation rate of the nitrogen vapor on the subcooled spray can be analytically modeled, and results validated and corrected by experimentally measuring the vapor condensation on liquid sprays.

Jurns, J. M.↗

NASA NTRS1991

LN2 spray droplet size measurement via ensemble diffraction technique

The size of subcooled liquified nitrogen droplets are measured with a 5 mW He-Ne laser as a function of pressure difference (delta P) across flat spray and full cone pressure atomizing nozzles. For delta P's of 3 to 30 psid, the spray sauter mean diameter (SMD) ranged between 250 to 50 microns. The pressure range tested is representative of those expected during cryogenic fluid transfer operations in space. The droplet sizes from the flat spray nozzles were greater than those from the full cone nozzle. A power function of the form, SMD varies as delta P(exp a), describes the spray SMD as a function of the delta P very well. The values of a were -0.36 for the flat spray and -0.87 for the full cone. The reduced dependence of the flat spray SMD on the delta P was probably because of: (1) the absence of a swirler that generates a turbulence within the nozzle to enhance atomization, and (2) a possible increase in shearing stress resulting from the delayed atomization due to the absence of turbulence. The nitrogen quality, up to 1.5 percent is based on isenthalpic expansion, did not have a distinct and measurable effect on the spray SMD. Both bimodal and monomodal droplet size population distributions were measured. In the bimodal distribution, the frequency of the first mode was much greater than the frequency of the second mode. Also, the frequency of the second mode was low enough such that a monomodal approximation probably would give reasonable results.

Saiyed, N. H.↗

NASA NTRS1991

LN2 spray droplet size measurement via ensemble diffraction technique

The size of subcooled liquified nitrogen droplets are measured with a 5 mW He-Ne laser as a function of pressure difference (delta P) across flat spray and full cone pressure atomizing nozzles. For delta P's of 3 to 30 psid, the spray sauter mean diameter (SMD) ranged between 250 to 50 microns. The pressure range tested is representative of those expected during cryogenic fluid transfer operations in space. The droplet sizes from the flat spray nozzles were greater than those from the full cone nozzle. A power function of the form, SMD varies as delta P(exp a), describes the spray SMD as a function of the delta P very well. The values of a were -0.36 for the flat spray and -0.87 for the full cone. The reduced dependence of the flat spray SMD on the delta P was probably because of: (1) the absence of a swirler that generates turbulence within the nozzle to enhance atomization, and (2) a possible increase in shearing stress resulting from the delayed atomization due to the absence of turbulence. The nitrogen quality, up to 1.5 percent is based on isenthalpic expansion, did not have a distinct and measurable effect on the spray SMD. Both bimodal and monomodal droplet size population distributions were measured. In the bimodal distribution, the frequency of the first mode was much greater than the frequency of the second mode. Also, the frequency of the second mode was low enough such that a monomodal approximation probably would give reasonable results.

Saiyed, N. H.↗