« Home « Chủ đề nhiệt động NIST

Chủ đề : nhiệt động NIST


Có 140+ tài liệu thuộc chủ đề "nhiệt động NIST"

Heat Transfer Handbook part 120

tailieu.vn

16.2c possesses highly conductive metal. 16.2d and e, have small resistance to liquid flow but are vulnerable to liquids oflow thermal conductivity. 16.2f was developed to reduce the thickness ofthe radial heat flow path through the structure and to provide a low-resistance path for the liquid flow from the condenser to the evaporator. 16.3 have a separate structure for develop-...

Heat Transfer Handbook part 121

tailieu.vn

TABLE 16.2 Expressions for the Effective Capillary Radius r c for Several Wick Structures. r eff = r r = radius ofliquid flow passage. The differential liquid pressure drop in the wick structure assuming one-dimen- sional laminar flow can be expressed as. KA w ρ l (16.12). f l · Re l (16.13). As the hydraulic radius ofthe porous structure...

Heat Transfer Handbook part 122

tailieu.vn

heat pipe with subsonic flow conditions and partial pressure recovery (some inertial effects are present in the vapor flow). Increasing the heat rejection rate and lowering the condenser temperature will decrease the evaporator temperature as shown in curve B. Continued increases in the heat flux and reductions in the condenser temperature will result in a decrease in the overall average...

Heat Transfer Handbook part 123

tailieu.vn

found using any of various solution techniques (e.g., the integral method) to transient heat conduction equation. Once the heat pipe condenser temperature and pressure decrease below the critical state and the working fluid corresponds to saturation conditions, the heat pipe is modeled using a coupled hydrodynamic rewetting model for an advancing liquid in the wick structure along with the heat...

Heat Transfer Handbook part 124

tailieu.vn

Akachi, H., and Polasek, F. Pulsating Heat Pipe Review ofthe Present State ofthe Art, Technical Report ITRI-ERL, Chutung, Taiwan, May.. Transient Heat Pipe Response and Rewetting Behavior, J. Heat Transfer . Experimental Investigation ofa Flexible Bellows Heat Pipe for Cooling Discrete Heat Sources, J. Heat Pipe Design Handbook, NASA Contract Report NAS5-23406.. Theory ofthe Ultimate Heat Transfer ofCylindrical Heat Pipes,...

Heat Transfer Handbook part 125

tailieu.vn

Figure 17.3 Steady-state temperature distributions in a continuously moving cylindrical rod for different values of L /D (4 Pe = VD/α = 0 . Figure 17.3 shows the results for the temperature distribution in a circular rod (γ = D/4) for one particular case. (17.4) reduces to. (17.4) and (17.6) are valid only when the value ofBi is sufficiently small,...

Heat Transfer Handbook part 126

tailieu.vn

Figure 17.9 Chip formation during orthogonal metal cutting. is assumed to be continuous, at least in the vicinity ofthe cutting tool, characteristic ofa ductile workpiece such as brass, low-carbon steel, or an aluminum alloy.. Plastic shear is the principal mechanism ofchip formation. There is a finite volume to the shear zone. Figure 17.9b shows the force components between the cutting...

Heat Transfer Handbook part 127

tailieu.vn

Figure 17.15 Coupled die and workpiece temperature distributions in wire drawing. (From Altan et al., 1983.). Figure 17.16 Coupled die and workpiece temperature distributions in metal extrusion. ements that are ignored in the discrete heat source approach (Yang, 1992). These include a Reynolds equation for the pressure distribution in a lubricating film for a given film thickness variation along the...

Heat Transfer Handbook part 128

tailieu.vn

process is influenced by the resin viscosity, which is a function of the temperature and degree ofcure in the laminate, and the applied pressure. Models for the consolidation process have been presented by Springer (1982), Davè et al. (1987), and Gutowski et al.. The models by Davè et al. (1987) and Gutowski et al. The fiber network also takes part...

Heat Transfer Handbook part 129

tailieu.vn

Normal Page PgEnds: TEX Void Growth (Microscopic Model) In the regions outside the consolidation rol-. lers, the tow matrix melt is exposed to the ambient atmospheric pressure (i.e., p f = p atm. The goal ofthe void growth analysis is therefore that ofdetermining the void fraction and tow thickness as a function of the axial location along the process (y...

Heat Transfer Handbook part 130

tailieu.vn

Figure 17.31 Comparison ofclosed-loop step responses ofa first-order thermal system with PI and thermostatic control.. 17.31 compares the closed-loop performance of a PID and a thermostatic controller with the differential gap during a step command to a desired temperature increase T d = 1000 K. First, the sampling period T can be se- lected by rules ofthumb based on the...

Heat Transfer Handbook part 131

tailieu.vn

A state matrix, dimensionless. B input matrix, dimensionless. C output matrix, dimensionless. 1298 HEAT TRANSFER IN MANUFACTURING AND MATERIALS PROCESSING. D direct matrix, dimensionless. G discrete state matrix, dimensionless h heat transfer coefficient, W/m 2 · K. I identity matrix, dimensionless. K controller matrix, dimensionless. L observer matrix, dimensionless. P pdrs matrix, dimensionless. input penalty matrix, dimensionless. 1300 HEAT TRANSFER...

Heat Transfer Handbook part

tailieu.vn

13th Technical Conference of the American Society for Composites, A. An Integral Approximate Solution ofHeat Transfer in the Grinding Process, Int. Microscale Heat Transfer. 18.1 Introduction. 18.2 Microscopic description of solids 18.2.1 Crystalline structure 18.2.2 Energy carriers 18.2.3 Free electron gas. 18.2.4 Vibrational modes of a crystal 18.2.5 Heat capacity. Electron heat capacity Phonon heat capacity 18.2.6 Thermal conductivity. 18.3...

Heat Transfer Handbook part 133

tailieu.vn

Figure 18.4 Plot of the frequency of a plane wave propagating in the crystal as a function of wavevector. By taking the time dependence of the solution to be of the form exp(−iωt), the frequency of the solution as a function of the wavevector can be determined as given by eq. (18.13). Figure 18.4 shows the results of this equation...

Heat Transfer Handbook part 134

tailieu.vn

The linear relation between the thermal conductivity and temperature in this regime arises from the linear temperature dependence of the electron heat capacity. At temperatures above the Debye temperature, the thermal conductivity is roughly independent of temperature as a result of competing temper- ature effects. (18.21. (18.35).. Lattice Thermal Conductivity Thermal conduction within the crystalline lattice is due primarily to...

Heat Transfer Handbook part 135

tailieu.vn

(18.63) and(18.67). Because both quantities are relatedlinearly to the relaxation time, their ratio is independent of the relaxation time:. T (18.68). (18.21) is usedfor the electron heat capacity. W · Ω/K 2 (18.69). 18.3.3 Molecular Approach. These approaches include lattice dynamic approaches (Tamura et al., 1999), molecular dynamic approaches (Voltz andChen, 1999. Lukes et al., 2000), andMonte Carlo simulations (Klistner...

Heat Transfer Handbook part 136

tailieu.vn

Normal Page PgEnds: TEX voltage, and the junction capacitance of the device. resent improvements, the insulating layer also decreases the ability of the device to dissipate heat. SOI transistors are an excellent example of a modern microelectronics device in which microscale heat transfer plays an important role in the overall device performance. Ju and Goodson (1999) cover the subject of...

Heat Transfer Handbook part 137

tailieu.vn

Direct Contact Heat Transfer. 19.1 Introduction. 19.2 Sensible heat exchange 19.2.1 General comments. 19.2.2 External convection to spheres 19.2.3 Heat transfer inside spheres 19.3 Evaporation andcondensation. 19.3.1 General considerations. 19.3.2 Condensation of a vapor on or in a liquid Film condenser. 19.3.3 Evaporation of a liquidby a surrounding vapor, gas or liquid Droplet evaporation in a vapor or gas. Droplet...

Heat Transfer Handbook part 138

tailieu.vn

These phenomena can be quite complicatedbecause of the various forms of unsteady steam flow that can exist. The heat transfer coefficients and the liquidtemperatures can experience wide-ranging time fluctuations here.. 19.3 andis discussedbelow.. If a steam jet is directedinto a liquidwater pool at lower mass flux rates (i.e., the lower-left-handregion of Fig. 19.3), a phenomenon denotedas chugging can occur.. (19.19)...

Heat Transfer Handbook part 139

tailieu.vn

Normal Page PgEnds: TEX Heat transfer results for liquid–liquidspray columns were correlatedby Plass et. For columns where vaporization is taking place, the heat transfer can be calculated as follows (Jacobs andBoehm, 1980):. 15 (19.45) To determine this result, data from a variety of systems were analyzed, including some where boiling took place on a liquidsurface.. U V = 894φ (19.46)....