Temperature In Radial Direction Research Articles

Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves

In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.

Stress analysis of rotating functionally graded polar orthotropic disk under thermomechanical loading

In this paper, thermo-elastic stress analysis of rotating variable thickness annular disk made of polar orthotropic functionally graded material (FGM) is presented. Elasticity modulus, density and thick-ness of the disk are assumed to vary radially according to a power law function. The material of the disk is assumed to be temperature dependent and different temperature distributions are assumed for variation of the temperature in radial direction. Radial stress and radial deformation of the disk with Clamped- Free (C-F) and Free-Free (F-F) boundary conditions are obtained using the numerical finite difference (FD) method. It is concluded that, by increasing the temperature variation, the radial stress and displacement increase. It is also observed that the radial stress in the rotating FG disk is more than the radial stress in rotating homogeneous disk and by increasing the FG index, the location of maximum stress in the disk shifts toward the outer surface. Also, the effects of temperature variation along the radius and orthotropy of the material on the radial stress and deformation are evaluated and concluded that their effect are significant. The results are compared with the available results in the literature and the good agreement between the present results and results in the literature shows the accuracy of FD method in thermo-elastic analysis of rotating FG orthotropic disk of variable thickness.

Strongly robust approach for temperature monitoring of power cable joint

This study aims to monitor the temperature inside power cable joint, with strong robustness to variable thermal environments and uncertain thermal parameters of the joint. The model consists of two sequential steps, radial-direction temperature inversion in the cable and axial-direction temperature inversion in the conductor. The former part was improved by coating the cable with a heat insulated layer, whereas the latter one was optimised through a proper parameter selection. Afterwards, an outdoor cable joint temperature-rise test was carried out and the temperature obtained from the proposed approach agrees well with the measured one. With the great change in ambient temperature and wind speed during the test, the model accuracy remains almost constant, and this is due to the heat insulated layer and low sensitivity coefficient of the algorithm. Besides, if the thermal conductivity and volumetric specific heat of waterproof compound in cable joint are assumed to increase by nearly five times, the maximum changes in temperature monitoring are only 1.4 and 0.4°C, respectively. The results indicate that this approach can effectively overcome the effects of variable thermal environments and thermal parameter dispersion in joint, thus promoting practical applications in temperature monitoring for cable joints.

Hotspot Temperature Monitoring of Fully Insulated Busbar Taped Joint

The fully insulated busbar has been extensively used in power and shipboard applications due to its favorable economic efficiency and excellent performance. Because of contact resistance and larger insulation thermal resistance, the joint, in certain circumstances, form a hotspot in the circuit. For hotspot temperature monitoring, therefore, this paper proposed an indirect approach which consists of radial direction temperature calculation (RDTC) in the busbar and axial direction temperature calculation (ADTC) in the conductor. The RDTC is to calculate the conductor temperatures from the surface temperatures of busbar in two different spots near the joint through the transient thermal network. The ADTC is to estimate the hotspot temperature from the conductor temperatures obtained in the RDTC using a fitted functional expression. The influence of solar radiation on the temperature distribution is greatly reduced by averaging the surface temperature in the RDTC and adjusting the functional form in the ADTC. A temperature-rise test on a practical insulated busbar taped joint was performed outdoors in hot summer to validate this approach. The calculated hotspot temperature agrees well with the measured result with a maximum error of only 3.8 K, indicating the high model precision and strong robustness to the solar radiation impact. Some factors in the applications of temperature monitoring are also discussed. This method is expected to be applied to the engineering application, thus improving the condition monitoring of the fully insulated busbar.

The exact regulation of temperature evolutions for droplet impact on ultrathin cold films at superhydrophilic surface

The present study reports a study of water droplets impacting on cold thin water films on a superhydrophilic surface. A thermal infrared imager was used to record the surface temperature distribution after the droplet impact on the liquid films. A ring-shaped high temperature zone was found after impact with the temperature first increasing and then gradually decreasing in the radial direction. Numerical simulations were then used to study the velocity distribution and the droplet motion inside the liquid film. The droplet spreading motion was restricted by liquid in the film for lower We which then reduces the heat transfer in that area and causes the formation of a ring-shaped high temperature distribution. The ring structure shape then changes with the increasing of We. This hot ring becomes wider and the temperature difference between the ring and the impact center decrease with the increasing of We. As We continues to increase, the ring-shaped temperature distribution disappears with the highest temperature at the center and the temperature in radial direction monotonically decreasing from the center to the edge. The initial film thickness also affects the temperature distribution after droplet impact. A thicker film causes the ring-shaped hot region to gradually move inward until it reaches the center and forms a hottest region in the impact center. Thus, the ring-shaped temperature distribution only occurs for lower We and thinner films. The shape and position of the temperature distribution after droplet impact on the cold, thin liquid films can then be precisely controlled by regulating the impact We and the initial film thickness. These results will greatly facilitate the design of precision spraying processes.

The transient separation of multicomponent mixtures in a cylindrical thermogravitational column

This work deals with the transient separation of a multicomponent mixture in a cylindrical thermogravitational column. The model describing the evolution of separation in vertical direction is derived and solved analytically. It is assumed that the profiles of velocity and temperature in radial direction are established and the forgotten effect as well as vertical diffusion in the column are ignored. The dependence of separation and characteristic transient time on the ratio of inner and outer cylinders radii δ is obtained. The transient time tends to diffusion time along the column height when δ approaches zero, while it reduces to the transient time for a flat–plate column when δ approaches unity. The analytical results are compared with two–dimensional numerical simulation for binary and ternary mixtures, and a good agreement is observed. It is concluded that for typical liquid mixtures, the decrease of radii ratio between inner and outer cylinders results in a slight increase of separation and in a significant increase of transient time.

Hot spot temperature inversion for the single-core power cable joint

Monitoring temperature inside the power cable joint is of great meaning to the safety of power distribution, while measuring it directly is infeasible. In this paper, the authors propose a new method to invert real-time hot spot temperature of conductor in the single-core power cable joint. This method consists of two parts, the radial-direction temperature inversion (RDTI) in the cable and axial-direction temperature inversion (ADTI) in the conductor. With this method, hot spot temperature of conductor in the cable joint could be figured out with the surface temperatures of the cable nearby the cable joint and load current, both of which are measurable. Then, the authors carry it out on an actual power cable joint in the laboratory, and the inversed temperatures are compared with experiment data, which come from the indoor experiment platform, to validate the availability of this method. The maximum error of this method is 6%, and it shows that this method for temperature inversion is feasible in laboratory scale.

Study of the radial direction temperature change law of the coil and control strategy in ultra-fast cooling

With the increasing demand for low-cost and high-performance hot-rolled strips, ultra-fast cooling technology is being rapidly developed. The process temperature control precision is an important factor that determines mechanical properties. Even though the process temperature is controlled, the longitudinal mechanical properties contribute to non-uniformity in thick strips. To reduce the longitudinal deviation, the unloaded coil radial direction temperature distribution under five cooling processes with initial temper- atures of 300 ◦ C, 400 ◦ C, 500 ◦ C and 600 ◦ C were systematically investigated. The radial direction temperature deviation change laws affected by the five cooling processes under different initial temperatures were obtained from calculation. With increasing tail special temperature/length, radial temperature deviation decreases gradually. Equations for cal- culating the temperature deviation of the center-external ring and internal-external ring under different initial temperatures were obtained. The study of temperature distribution in a 10-mm-thick strip provided guidance for the tail process planning in strips of other thicknesses. Based on the research, the progressive-U cooling strategy was suggested to de- crease longitudinal property deviation in high-quality steel production. The strategy was successfully applied in a commercial trial production with high accuracy control, laying a solid foundation for high-quality product development.

Temperature Distribution Inside Hot Water Storage Tanks of Solar Collectors

An analytical experimental investigation into the temperature field inside the hot water storage tank of a solar collector was carried out. A transient two-dimensional semi-infinite cylindrical length model with time-and-space boundary-conditions dependency was selected. Conduction and convection heat-transfer modes in the axial direction together with conduction in the radial direction were neglected, since these were considered to be small in comparison with the axial conduction and convection diffusion terms, which in turn were considered small relative to the energy stored. Good agreement between theoretical and experimental prediction was verified. The radial direction temperature dependency disappeared for axial lengths greater than one quarter of the tank depth for most practical operating conditions especially for low inflow velocities and low inlet to outlet temperature ratios. The axial conduction term in the governing equation can be dropped out for inflow velocities greater than a certain critical value without distorting the theoretical consequences. Temperature profiles in the axial direction of a cylindrical storage tank can be assumed to be linear especially for high inflow velocities as well as low temperature differences at inlet and outlet of the storage tank.

Temperature distribution inside hot-water storage tanks of solar collectors

An analytical-experimental investigation into the temperature field inside the hot-water storage tank of a solar collector is carried out. A transient two-dimensional semi-infinite cylindrical length model with time and space boundary conditions dependency is selected. Conduction and convection heat transfer modes in the axial direction together with conduction in the radial direction are considered. Good agreement between theoretical and experimental predictions is verified. The radial direction temperature dependency disappears for axial lengths greater than one quarter of the tank depth for most practical operating conditions especially for low inflow velocities and low inlet to outlet temperature ratios. The axial conduction term in the governing equation can be dropped out for inflow velocities greater than a certain critical value without disturbing the theoretical consequences. Temperature profiles in the axial direction can be assumed to be linear especially for high inflow velocities as well as low temperature differences at inlet and outlet of the storage tank.