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Kamotani, Y.

Publications and source records attributed to Kamotani, Y..

29 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Thermal convection in an enclosure due to vibrations aboard spacecraft

The paper discusses thermal convection in an enclosure induced by spacecraft vibrations (g-jitter). Under normal circumstances (no maneuvers, no intentional spinning of the spacecraft) the g-jitter generates predominantly oscillatory velocity and temperature fields with zero time-mean values. The g-jitter can also generate secondary flows with non-zero mean, but they are of much smaller order. Some implications of the g-jitter on materials processing in space are discussed

Kamotani, Y.↗
NASA NTRS1978

User's Manual for Thermal Analysis Program of Axially Grooved Heat Pipe (HTGAP)

A computer program that numerically predicts the steady state temperature distribution inside an axially grooved heat pipe wall for a given groove geometry and working fluid under various heat input and output modes is described. The program computes both evaporator and condenser film coefficients. The program is able to handle both axisymmetric and nonaxisymmetric heat transfer cases. Non-axisymmetric heat transfer results either from non-uniform input at the evaporator or non-uniform heat removal from the condenser, or from both. The presence of a liquid pool in the condenser region under one-g condition also causes non-axisymmetric heat transfer, and its effect on the pipe wall temperature distribution is included in the present program. The hydrodynamic aspect of an axially grooved heat pipe is studied in the Groove Analysis Program (GAP). The present thermal analysis program assumes that the GAP program (or other similar programs) is run first so that the heat transport limit and optimum fluid charge of the heat pipe are known a priori.

Kamotani, Y.↗
NASA NTRS1978

Evaporator film coefficients of grooved heat pipes

The heat transfer rate in the meniscus attachment region of a grooved heat pipe evaporator is studied theoretically. The analysis shows that the evaporation takes place mainly in the region where the liquid changes its shape sharply. However, comparisons with available heat transfer data indicate that the heat transfer rate in the meniscus varying region is substantially reduced probably due to groove wall surface roughness.

Kamotani, Y.↗
NASA NTRS1977

Effects of one-sided heat input and removal on axially grooved heat pipe performance

The performance of an axially grooved heat pipe with one-sided heat input and removal was investigated analytically. Under zero-g condition the maximum heat transport of the pipe may decrease as much as 30% depending on the liquid slug behavior in the condenser section. In one-g environment the performance depends mainly on the fluid charge. The maximum heat transport, if over-charged, is almost equal to the value for uniform heating and cooling due to puddling effect. However, for some heater-cooler combinations the temperature drop across the heat pipe becomes very large. Computed results for tilted heat pipes compare favorably with available experimental data.

Kamotani, Y.↗
NASA NTRS1976

Thermal Analysis of Axially Grooved Heat Pipes

The liquid viscous drag and the evaporator film coefficient were determined analytically for a heat pipe with axial rectangular grooves under zero-g conditions. The liquid pressure drop and the evaporator film coefficient for an axially grooved heat pipe were found to be expressed by the functions of the meniscus angle, which makes it possible to predict its performance analytically. The performance near its capillary pumping limit is influenced by the contact angle.

Kamotani, Y.↗
NASA NTRS1976

Analysis of axially grooved heat pipe condensers

In an analytical study of the thermal behavior of the condenser section of a heat pipe with axial rectangular grooves under zero-g condition, the condensation rate was determined by studying the motion of the thin liquid film on the land area between grooves. It was found that the local condensation rate depends, among other factors, on the curvature of the liquid meniscus and on the shape of the land top. Computed overall heat transfer rate compares favorably with available experimental data. The liquid meniscus variation along the heat pipe length in the condenser section was also determined.

Kamotani, Y.↗
NASA NTRS1974

Experiments on confined turbulent jets in cross flow

Results are reported of experiments on the effects of an opposite wall on the characteristics of turbulent jets injected into a cross flow, for unheated and heated jets. Longitudinal and transverse distributions of velocity and temperature are presented for single and multiple circular jets, and trajectories are presented for two-dimensional jets. The opposite wall has relatively little effect on a single jet unless the ratio of jet to cross flow momentum flux is large enough for the jet to impinge on the opposite wall. For a row of jets aligned perpendicularly to the cross flow, the opposite wall exerts progressively larger influence as the spacing between jets decreases. Much of the effect of jet and wall proximity can be understood by considering the interaction of the vortex flow which is the major feature of the structure of a single jet in a cross flow. Smoke photographs are shown to elucidate some of the interaction patterns.

Kamotani, Y.↗
NASA NTRS1973

Experiments on confined turbulent jets in cross flow.

Results are reported of experiments on the effects of an opposite wall on the characteristics of turbulent jets injected into a cross flow, for unheated and heated jets. Longitudinal and transverse distributions of velocity and temperature are presented for single and multiple circular jets, and trajectories are presented for two-domensional jets. The opposite wall has relatively little effect on a single jet unless the ratio of jet to cross flow momentum flux is large enough for the jet to impinge on the opposite wall. For a row of jets aligned perpendicularly to the cross flow, the opposite wall exerts progressively larger influence as the spacing between jets decreases. Much of the effect of jet and wall proximity can be understood by considering the interaction of the vortex flow which is the major feature of the structure of a single jet in a cross flow. Smoke photographs are shown to elucidate some of the interaction patterns.

Kamotani, Y.↗
NASA NTRS1972

Investigations of a turbulent jet in a crossflow

Analyses of flow field downstream of jet directed at right angles into crossflow for heated and unheated single jets are presented. Application of flow data to cooling system for gas turbine combustion chambers is discussed. Temperature distribution, velocity trajectory, and vortex motion are described.

Kamotani, Y.↗
NASA NTRS1972

Experiments on a turbulent jet in a cross flow.

Results are reported of experiments on turbulent circular jets issuing into a cross flow, both for unheated and heated jets. Longitudinal and transverse distributions of velocity, temperature, and turbulence intensity are presented. The velocity distributions depend mainly on the ratio of jet to cross flow momentum flux. The temperature distributions depend also on the density ratio. The jet structure is dominated by a vortex wake which forms behind the jet, which is evident both from the detail measurements and from smoke photographs of the flow. The experiments also indicate that the components of cross flow normal and parallel to the jet trajectory independently control the entrainment rate.

Kamotani, Y.↗