A 1-D/2-D model and experimental results for a closed-loop thermosyphon with vertical heat transfer sections

1992 ◽  
Vol 35 (11) ◽  
pp. 2969-2982 ◽  
Author(s):  
M.A. Bernier ◽  
B.R. Baliga
Author(s):  
Bhawna Verma ◽  
V. L. Yadav ◽  
K. K. Srivastava

2008 ◽  
Vol 136 (10) ◽  
pp. 3863-3872 ◽  
Author(s):  
Kerry Emanuel ◽  
Jeff Callaghan ◽  
Peter Otto

Tropical cyclones moving inland over northern Australia are occasionally observed to reintensify, even in the absence of well-defined extratropical systems. Unlike cases of classical extratropical rejuvenation, such reintensifying storms retain their warm-core structure, often redeveloping such features as eyes. It is here hypothesized that the intensification or reintensification of these systems, christened agukabams, is made possible by large vertical heat fluxes from a deep layer of very hot, sandy soil that has been wetted by the first rains of the approaching systems, significantly increasing its thermal diffusivity. To test this hypothesis, simulations are performed with a simple tropical cyclone model coupled to a one-dimensional soil model. These simulations suggest that warm-core cyclones can indeed intensify when the underlying soil is sufficiently warm and wet and are maintained by heat transfer from the soil. The simulations also suggest that when the storms are sufficiently isolated from their oceanic source of moisture, the rainfall they produce is insufficient to keep the soil wet enough to transfer significant quantities of heat, and the storms then decay rapidly.


Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 595
Author(s):  
Mahir Faris Abdullah ◽  
Rozli Zulkifli ◽  
Hazim Moria ◽  
Asmaa Soheil Najm ◽  
Zambri Harun ◽  
...  

Impinging jets are considered to be a well-known technique that offers high local heat transfer rates. No correlation could be established in the literature between the significant parameters and the Nusselt number, and investigation of the interactions between the correlated factors has not been conducted before. An experimental analysis based on the twin impingement jet mechanism was achieved to study the heat transfer rate pertaining to the surface plate. In the current paper, four influential parameters were studied: the spacing between nozzles, velocity, concentration of Nano solution coating and nozzle-plate distance, which are considered to be effective parameters for the thermal conductivity and the heat transfer coefficient of TiO2 nanoparticle, an X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis were done, which highlighted the structure and showed that the nanosolution coated the surface homogenously. Moreover, a comparison was done for the experimental results with that of the predicted responses generated by the Design Expert software, Version 7 User’s Guide, USA. A response surface methodology (RSM) was employed to improve a mathematical model by accounting for a D-optimal design. In addition, the analysis of variance (ANOVA) was employed for testing the significance of the models. The maximum Nu of 91.47, where H = S = 1 cm; Reynolds number of 17,000, and TiO2 nanoparticle concentration of 0.5% M. The highest improvement rate in Nusselt was about 26%, achieved with TiO2 Nanoparticle, when S = 3 cm, H = 6 cm and TiO2 nanoparticle = 0.5 M. Furthermore, based on the statistical analysis, the expected values were found to be in satisfactory agreement with that of the empirical data, which was conducted by accounting for the proposed models’ excellent predictability. Multivariate approaches are very useful for researchers, as well as for applications in industrial processes, as they lead to increased efficiency and reduced costs, so the presented results of this work could encourage the overall uses of multivariate methods in these fields. Hypotheses: A comparison was done for the predicted responses generated by the Design Expert software with the experimental results and then studied to verify the following hypotheses: ► Preparation of three concentrations of TiO2 nanosolution was done and studied. ► The heat transfer rate could be increased by surface coating with TiO2 nanoparticle. ► The heat transfer could be improved by the impingement jet technique with suitable adjustments.


Lubricants ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 26
Author(s):  
Nico Buchhorn ◽  
Michael Stottrop ◽  
Beate Bender

In tilting-pad journal bearings (TPJB) with a non-flooded lubrication concept, higher maximum pad temperatures occur than with a flooded bearing design due to the lower convective heat transfer at the pad edges. In this paper, we present an approach to influence the thermal behavior of a five-pad TPJB by active cooling. The aim of this research is to investigate the influence of additional oil supply grooves at the trailing edge of the two loaded pads on the maximum pad temperature of a large TPJB in non-flooded design. We carry out experimental and numerical investigations for a redesigned test bearing. Within the experimental analysis, the reduction in pad temperature is quantified. A simulation model of the bearing is synthesized with respect to the additional oil supply grooves. The simulation results are compared with the experimental data to derive heat transfer coefficients for the pad surfaces. The experimental results indicate a considerable reduction of the maximum pad temperatures. An overall lower temperature level is observed for the rear pad in circumferential direction (pad 4). The authors attribute this effect by a cooling oil carry-over from the previous pad (3). Within the model limits, a good agreement of the simulation and experimental results can be found.


Sign in / Sign up

Export Citation Format

Share Document