Using Servo-Drive Presses to Determine the Effect of Blank Holder Pressure on Temperature Change in Warm Forming of Sheet

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Serhat Kaya
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Temperature Change ◽  
Warm Forming ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Servo Drive ◽  
Blank Holder ◽  
Heat Transfer Coefficients ◽  
Deform 2D

Heat transfer coefficient (HTC) is one of the most important and difficult-to-obtain parameter in high temperature environment. Contact pressure and workpiece surface roughness are among important parameters that affect the heat transfer in elevated temperature forming of sheets. In this study, HTCs are investigated experimentally by using a servo-drive press. With the flexibility that the servo-drive press offers, effect of various blank holder pressures on temperature change is determined. Before and after surface roughness conditions of aluminum and magnesium (from two different manufacturers) alloy sheets are compared. Experimental setup was modeled using deform 2d, and measured temperature curves were compared with the finite element analysis (FEA) predictions and a window of heat transfer coefficients were determined for warm forming of sheets. Determined heat transfer coefficients were implemented in a nonisothermal deep drawing FE model in deform 2d and results were compared with experiments. Good agreement was obtained between FEA predictions and experiments.

Advantages of Servo Presses in Metal Forming With a Focus on Warm Forming of Sheets

2010 ◽  
Author(s):  
Serhat Kaya ◽  
Taylan Altan
Keyword(s):  
Heat Transfer ◽  
Metal Forming ◽  
Warm Forming ◽  
Measured Temperature ◽  
Servo Motor ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Forming Technology ◽  
Cup Drawing ◽  
Good Agreement

Servo presses are recently introduced metal forming machinery and they are in many ways, a hybrid of mechanical and hydraulic presses. They are designed to combine the strengths of conventional mechanical and hydraulic presses, and at the same time to minimize their constraints. The advantages of servo presses in metal forming technology are discussed briefly. Advantages they offer in warm forming are discussed more in detail and demonstrated experimentally. By using the flexibility that the servo press offers, the effect of contact pressure on temperature change and surface roughness of aluminum and magnesium sheet is experimentally investigated. Non-isothermal warm forming is introduced and studied experimentally. Combined advantages of the non-isothermal approach and the servo motor controlled press are demonstrated by introducing a variable forming speed concept. As a result, 60% savings in cup drawing time is achieved experimentally. Measured temperature curves were used in FEA to determine heat transfer coefficients. Effect of the determined heat transfer coefficients on deep drawing was analyzed using FEA and good agreement were obtained between FEA predictions and experimental measurements.

Effect of Surface Roughness on Pool Boiling Heat Transfer of Water on a Superhydrophilic Aluminum Surface

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Jinsub Kim ◽  
Seongchul Jun ◽  
Jungho Lee ◽  
Juan Godinez ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Boiling Heat Transfer ◽  
Aluminum Surface ◽  
Transfer Coefficients ◽  
Copper Surfaces ◽  
Heat Transfer Coefficients ◽  
Superhydrophilic Surface ◽  
Aluminum Surfaces ◽  
Effect Of Surface

The effect of surface roughness on the pool boiling heat transfer of water was investigated on superhydrophilic aluminum surfaces. The formation of nanoscale protrusions on the aluminum surface was confirmed after immersing it in boiling water, which modified surface wettability to form a superhydrophilic surface. The effect of surface roughness was examined at different average roughness (Ra) values ranging from 0.11 to 2.93 μm. The boiling heat transfer coefficients increased with an increase in roughness owing to the increased number of cavities. However, the superhydrophilic aluminum surfaces exhibited degradation of the heat transfer coefficients when compared with copper surfaces owing to the flooding of promising cavities. The superhydrophilic aluminum surfaces exhibited a higher critical heat flux (CHF) than the copper surfaces. The CHF was 1650 kW/m2 for Ra = 0.11 μm, and it increased to 2150 kW/m2 for Ra = 0.35 μm. Surface roughness is considered to affect CHF as it improves the capillary wicking on the superhydrophilic surface. However, further increase in surface roughness above 0.35 μm did not augment the CHF, even at Ra = 2.93 μm. This upper limit of the CHF appears to result from the hydrodynamic limit on the superhydrophilic surface, because the roughest surface with Ra = 2.93 μm still showed a faster liquid spreading speed.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

Calibration of External Heat Transfer Coefficients During Cooling of a Partially-Filled Water Tank Using Measured Temperature-Time Data

2018 ◽  
Author(s):  
Vishal Ramesh ◽  
Sandip Mazumder ◽  
Gurpreet Matharu ◽  
Dhaval Vaishnav ◽  
Syed Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Measured Temperature ◽  
Water Tank ◽  
Time Data ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature Time

A combined Computational Fluid Dynamics (CFD) and experimental approach is presented to determine (calibrate) the external convective heat transfer coefficients (h) around a partially-filled water tank cooled in a climactic chamber. A CFD analysis that includes natural convection in both phases (water and air) was performed using a 2D-axisymmetric tank model with three prescribed average heat transfer coefficients for the top, side and bottom walls of the tank. The commercial CFD code ANSYS-Fluent™, along with User-Defined Functions (UDFs), were utilized to compute and extract temperature vs. time curves at five different thermocouple locations within the tank. The prescribed h values were then altered to match experimentally obtained temperature-time data at the same locations. The calibration was deemed successful when results from the simulations exhibited match with experimental data within ±2°C for all thermocouples. The calibrated h values were finally used in full-scale 3D simulations and compared to the experimental data to test their accuracy. Predicted 3D results were found to agree with experimental results within the error of the calibration, thereby lending credibility to the overall approach.

Design of an axially concave pad profile for a large turbine tilting-pad bearing

2016 ◽  
Vol 231 (4) ◽  
pp. 479-488 ◽  
Author(s):  
Sebastian Kukla ◽  
Nico Buchhorn ◽  
Beate Bender
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Load Capacity ◽  
Measurement Data ◽  
Tangential Direction ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Tilting Pad ◽  
Calculation Results

To improve operational safety and/or achieve a higher load capacity of turbine tilting-pad bearings, an axially concave pad profile is presented. The thermal and mechanical stress of the loaded pads of a test bearing in load between pivot configuration has been analysed. Both film thickness and pressure distribution have been measured at a very high resolution. A fluid film calculation program in combination with a finite-volume-based structural mechanics program is used to simulate the deformation of a single pad under high circumferential speeds. In this context, the axial and tangential heat transfer coefficients of the pad surface, which act as boundary conditions for the calculation of the 3D temperature distribution, are determined using an optimization process. Herein, the match of predicted and measured pad temperatures is the goal. It can be shown that there must be a huge difference in heat transfer in axial and tangential direction in order to match the large measured temperature gradient in circumferential direction. Based on the measured deformed profile the program code is used to derive a concave pad profile, which will result in an axially non-arched sliding surface under the expected thermal load. Therefore, an iterative simulation procedure is used. By decreasing the axial arching of the pad and thus the large film thickness at the axial ends using an improved profile designed for a specific operation point, the minimum film thickness and maximum pad temperature can be influenced beneficially. The comparison of measurement data and calculation results shows very good agreement regarding the pad deformations. The results indicate that by axially concave profiling of the loaded pads of a large tilting-pad bearing for a specific operation point, the static characteristics in the form of temperature, film thickness and load capacity can be improved.

Numerical and Experimental Study of Heat Transfer in a BIPV-Thermal System

2007 ◽  
Vol 129 (4) ◽  
pp. 423-430 ◽  
Author(s):  
L. Liao ◽  
A. K. Athienitis ◽  
L. Candanedo ◽  
K.-W. Park ◽  
Y. Poissant ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Wave Radiation ◽  
Measured Temperature ◽  
Cfd Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients ◽  
T System

This paper presents a computational fluid dynamics (CFD) study of a building-integrated photovoltaic thermal (BIPV∕T) system, which generates both electricity and thermal energy. The heat transfer in the BIPV∕T system cavity is studied with a two-dimensional CFD model. The realizable k‐ε model is used to simulate the turbulent flow and convective heat transfer in the cavity, including buoyancy effect and long-wave radiation between boundary surfaces is also modeled. A particle image velocimetry (PIV) system is employed to study the fluid flow in the BIPV∕T cavity and provide partial validation for the CFD model. Average and local convective heat transfer coefficients are generated with the CFD model using measured temperature profile as boundary condition. Cavity temperature profiles are calculated and compared to the experimental data for different conditions and good agreement is obtained. Correlations of convective heat transfer coefficients are generated for the cavity surfaces; these coefficients are necessary for the design and analysis of BIPV∕T systems with lumped parameter models. Local heat transfer coefficients, such as those presented, are necessary for prediction of temperature distributions in BIPV panels.

Investigation of Circumferential Variation of Heat Transfer Coefficients During In-Tube Evaporation for R-22 and R-407C Using Liquid Crystal

2002 ◽  
Vol 124 (5) ◽  
pp. 845-853 ◽  
Author(s):  
Seok Ho Yoon ◽  
Min Soo Kim
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Cross Sections ◽  
Outer Wall ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Measured Temperature ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Heat transfer coefficients during evaporation in a horizontal smooth tube for R-22 and R-407C (R-32/125/134a, 23/25/52 wt.%) have been measured using thermochromic liquid crystal. Focus has been put on the circumferential variation of heat transfer coefficients at several cross-sections of the test tube with inner diameter of 11.3 mm for several vapor qualities of refrigerant. The inner wall temperatures were calculated by one dimensional heat conduction equation from the measured outer wall temperatures, which were obtained using an image processing technique with thermochromic liquid crystal (TLC). The relation between measured temperature and color information (Red-Green-Blue values) of thermochromic liquid crystal was calibrated by a neural network method. Results show that circumferential variation of heat transfer coefficients for R-22 is quite large with the highest heat transfer coefficient at the top of the tube. For zeotropic mixture of R-407C, similar trend has been observed with less difference between the heat transfer coefficients at the top and bottom than that of R-22.

Effect of Surface Roughness on Pool Boiling Heat Transfer of Water on a Superhydrophilic Aluminum Surface

2016 ◽  
Author(s):  
Jinsub Kim ◽  
Seongchul Jun ◽  
Jungho Lee ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Boiling Heat Transfer ◽  
Aluminum Surface ◽  
Transfer Coefficients ◽  
Copper Surfaces ◽  
Heat Transfer Coefficients ◽  
Superhydrophilic Surface ◽  
Aluminum Surfaces ◽  
Effect Of Surface

The effect of surface roughness on the pool boiling heat transfer of water was investigated on superhydrophilic aluminum surfaces. The formation of nanoscale protrusions on the aluminum surface was confirmed after immersing it in boiling water, which modified surface wettability to form a superhydrophilic surface. The effect of surface roughness was examined at different average roughness (Ra) values ranging from 0.11–2.93 μm. The boiling heat transfer coefficients increased with an increase in roughness owing to the increased number of cavities. However, the superhydrophilic aluminum surfaces exhibited degradation of the heat transfer coefficients when compared with copper surfaces owing to the flooding of promising cavities. The superhydrophilic aluminum surfaces exhibited a higher critical heat flux (CHF) than the copper surfaces. The CHF was 1,650 kW/m2 for Ra = 0.11 μm, and it increased to 2,150 kW/m2 for Ra = 0.35 μm. Surface roughness is considered to affect CHF as it improves the capillary wicking on the superhydrophilic surface. However, further increase in surface roughness above 0.35 μm did not augment the CHF, even at Ra = 2.93 μm. This upper limit of the CHF appears to result from the hydrodynamic limit on the superhydrophilic surface, because the roughest surface with Ra = 2.93 μm still showed a faster liquid spreading speed.

Sign in / Sign up

Export Citation Format

Share Document