scholarly journals Thermal Simulation for a Mechanical Spindle With External Cooler Across Grease Coated Interface

2021 ◽  
Author(s):  
Liang Zhao ◽  
Mohan Lei ◽  
Hongdi Ren ◽  
Jinshi Wang ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Cooling System ◽  
Thermal Error ◽  
Element Model ◽  
Internal Cooling ◽  
Heavy Load ◽  
Silicone Grease ◽  
Total Thermal Resistance ◽  
Rotating Speed ◽  
External Cooling

Abstract Spindles in precision boring machine often work in low speed and heavy load without internal cooling, and the thermal error is nonnegligible. So an external cooling system was designed, and the effectiveness of the designed scheme needs to be preliminarily verified by simulation before building the cooling system. Thermal simulations of the spindle with an external cooler require calculating the thermal resistance of the thermal grease-coated interface between the cooler and spindle. Models describing the contact thermal resistance and total thermal resistance for metal contact filled with silicone grease based on solid-liquid interface force equivalence were described in this paper, and experiments were also conducted to verify the accuracy of these models. The contact thermal resistances between the cast iron/copper and silicone grease on flat or arc surfaces were calculated, and the bulk thermal resistance of the silicone grease layer was calculated. The total heat transferred between the cooler and the silicone grease-coated interface of the spindle were calculated. Heat transfer and heat generation in the spindle were calculated, and a finite element model was established to verify the effectiveness of the designed external cooling scheme. Finally, results from experiments for the spindle in different conditions show that the external cooling system decreases the time to reach thermal equilibrium by more than 60%. The RMSE of the simulated thermal elongation is less than 5.7044 μm when the rotating speed of 3000 rpm, and is less than 3.9714 μm when the rotating speed is 1500 rpm.

Thermal error controlling for the spindle in a precision boring machine with external cooling across coated joints

2019 ◽  
Vol 234 (2) ◽  
pp. 658-675
Author(s):  
Mohan Lei ◽  
Gedong Jiang ◽  
Liang Zhao ◽  
Jinshi Wang ◽  
Ben Q Li ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Thermal Equilibrium ◽  
Evaluation Method ◽  
Control Method ◽  
Thermal Error ◽  
Joint Surface ◽  
Internal Cooling ◽  
Equilibrium Time ◽  
External Cooling ◽  
Boring Machines

Spindles in precision boring machines usually operate without internal cooling, and thermal error in such spindles is nonnegligible and can severely affect the end-processing quality of the machines. This study aims to investigate the effects that external cooling exerts on the thermal behavior of such spindles. A helical tube cooler is taken for external cooling. An analytical thermal resistance model for the grease-coated cooler-housing joint surface, which considers the pressured cambered-flat contact pair and rough metal surface-grease contact, is presented and validated, and a numerical thermal–fluid–solid coupling model for the cooler-spindle system is then established. An evaluation method is put forward to obtain the stability of the thermal error, which determines the boring processing accuracy and thermal equilibrium time, from experimental data. Then, the external cooling was optimally designed based on the simulation results from the numerical model. Experiments show that the designed cooler reduced the thermal equilibrium time by 47.13% and the maximum thermal error by 81.7%, and the proposed model can accurately predict the cooling effect on the spindle thermal behavior. This study not only provides a thermal error control method for the spindle but is expected to advance the theoretical basis of cooling design for complex electromechanical systems.

Comprehensive Reduction of Thermal Resistance in Air Cooled Condensers

2015 ◽  
Author(s):  
Ahmad Saleh ◽  
Jayanta Kapat
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Transfer Process ◽  
Cooling System ◽  
Ambient Air ◽  
Heat Transfer Process ◽  
Air Cooling ◽  
Total Thermal Resistance ◽  
Fin Efficiency

Restriction on water consumption is becoming an increasing problem for the power generation industry. As an alternative both to once-through cooling and to surface condenser/wet-cooling tower combination, utility companies and equipment manufacturers are considering, and even implementing, air-cooled condenser (ACC). However, the industry is quite reluctant to switch over to ACC for three important reasons: (a) lower power output, (b) higher capital cost, and (c) larger physical foot-print, all because of the same reason — it is not as efficient to transfer heat from condensing steam to air as it is to transfer to water. In other words, overall thermal resistance from condensing steam to the ambient air is significantly higher than to cooling water. To get a clear and full understanding of the heat transfer process occur in air-cooling condenser, Detailed mathematical equations were derived to model the heat transfer process through the fined-tubes of the ACC. The total thermal resistance model was analyzed and investigated to identify the design components with highest affect in the process. The paper proposes a viable cooling system based on novel heat pipe technology which addresses these problems. This technology employs boiling as the means to store and transfer heat energy. A detailed mathematical set of equations was derived to model the heat pipe thermal resistance. A comparison of the heat transfer performances of the ACC technology and the proposed method is presented. The proposed cooling system suggests a solution for each of the three components of the thermal resistance, the super-hydrophobic coating of the steam ducts internal surfaces increased the condensing heat transfer rate by an order of magnitude, the proposed design of the heat pipes improved the external heat transfer, and the installation mechanism improves the fin efficiency by eliminating the contact resistance between steam duct and the heat pipe.

scholarly journals Analysis for the heat transfer of fully tempered vacuum glazing based on the thermal resistance model and finite element model

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879598 ◽  
Author(s):  
Dongfang Hu ◽  
Yichen Li ◽  
Chang Liu ◽  
Yanbing Li
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Conduction ◽  
Finite Element Model ◽  
Thermal Resistance ◽  
Element Model ◽  
Unit Cell ◽  
Hertzian Contact ◽  
Total Thermal Resistance ◽  
Vacuum Glazing

The fully tempered vacuum glazing, consisting of two fully tempered glass plates detached through a limited vacuum medium (below 0.01 Pa), is presented. The heat transfer through fully tempered vacuum glazing is complex, including heat conduction, thermal radiation, and convection. To analyze heat conduction through a stainless steel support ball, the thermal resistance of the support ball is established based on Hertzian contact model. And the total thermal resistance of the unit cell with one support ball is defined. The three-dimensional finite element model for a center unit cell of fully tempered vacuum glazing is simulated to validate the result of the total thermal resistance. The simulation transmission U-values are 0.26 W/m2 K. Meanwhile, the simulation transmission U-values of entire fully tempered vacuum glazing are 0.84 W/m2 K without frame insulation.

PERFORMANCE OF A MULTI-STACK MICROCHANNEL HEAT SINK

2016 ◽  
Vol 78 (10-2) ◽  
Author(s):  
Nik Mohamad Sharif ◽  
Normah Mohd Ghazali
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
Cooling System ◽  
Heat Fluxes ◽  
Width Ratio ◽  
Optimum Number ◽  
Microchannel Heat Sink ◽  
Objective Functions ◽  
Pumping Power ◽  
Total Thermal Resistance

The usage of a very large scale integrated circuits generate high heat fluxes and require an effective cooling system. A microchannel heat sink (MCHS) is one of the reliable cooling systems that had been applied. In terms of performance, a MCHS can be appraised by obtaining low total thermal resistance and pumping power. However, as the total thermal resistance decreases, the pumping power will increase. A few studies have been focused on the minimization of the thermal resistance and pumping power of a multi-stack MCHS. Optimization of two objective functions which are the total thermal resistance and pumping power has been done by using genetic algorithm. It is demonstrated that both objective functions can be minimized by optimizing two design variables which are the channel aspect ratio, , and wall width ratio, . It was found that the usage of a stacked configuration for the MCHS is able to reduce the total thermal resistance. From the optimization, it was found that the optimum number of stacks that can be implemented is three. With the three-stack configuration, the total thermal resistance found is 0.1180 K/W which is 21.8% less compared to the single-stack MCHS. However, the pumping power needed for the three-stack MCHS is increased by 0.17 % compared to single-stack which is 0.7535 W.

Experimental Study on Flow and Heat Transfer Characteristics in a Microscale Heat Exchanger

2007 ◽  
Author(s):  
Tao Wang ◽  
Xuegong Hu ◽  
Dawei Tang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Exchanger ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Laser Cooling ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
Distilled Water ◽  
Total Thermal Resistance

To solve the questions of the middle heat exchanger of space-based laser cooling system such as large heat transfer area and operating mode instability, a MC-MG (Microchannel-Microgroove) microscale heat exchanger is proposed and experimental study is carried out. The experimental results indicate that as the Reynolds number increases, the Nusselt number originally increases and then keeps constant. While adding the volumetric flow rate of distilled water in the microchannels, the total thermal resistance is first reduced and then becomes steady. With increasing the volumetric flow rate of distilled water, the total quantity of heat transfer increases first, then decreases and finally tends to be constant. The average heat transfer coefficient of the heat exchanger reaches to 1.6 × 104W/ (m2-K) and total thermal resistance is less than 0.21K/W. Therefore the solution to cooling laser with the heat exchanger is preferable.

scholarly journals Testing of thermal fatigue resistance of tools and rolls for hot working

2017 ◽  
Vol 64 (3) ◽  
pp. 161-168 ◽  
Author(s):  
Milan Terčelj ◽  
Matevž Fazarinc ◽  
Goran Kugler
Keyword(s):  
Thermal Fatigue ◽  
Fatigue Testing ◽  
Cooling System ◽  
Base Material ◽  
Internal Cooling ◽  
Cast Irons ◽  
Present Contribution ◽  
Heating And Cooling ◽  
External Cooling ◽  
Roll Steels

Abstract In the present contribution two tests for thermal fatigue testing, which have been developed in our group, are presented. First test has provided internal cooling system of sample, while second has external cooling. For both tests heating and cooling of samples are computer guided that enables very reliable results of testing. The first test is more appropriate for testing the base material, i.e. roll cast irons, roll steels, tool steels. The second test is more appropriate for experiments that are aimed for selection of appropriate tool surface treatment, i.e. laser cladding, nitriding, coating, etc., and to compare and to achieve improved resistance against thermal fatigue of produced surface layers.

Thermal Performances Analysis of Microelectronic Chip Cooling System with Thermoelectric Components

2011 ◽  
Vol 216 ◽  
pp. 128-133 ◽  
Author(s):  
Chang Hong Wang ◽  
Jiang Yun Zhang ◽  
Jin Huang
Keyword(s):  
Thermal Resistance ◽  
Cooling System ◽  
Dominant Role ◽  
Test System ◽  
Peltier Effect ◽  
Thermoelectric Cooling ◽  
Analysis Model ◽  
Total Thermal Resistance ◽  
Chip Cooling ◽  
Operating Current

The microelectronic chip thermoelectric cooling equipment and its test system have been developed for the deficiency of the conventional cooling technologies in this paper. The thermal resistance analysis model was applied in research the heat transfer process of the microelectronic chip cooling system and its characteristics. The results show that: When the thermoelectric cooling (TEC) system is in normal operating condition,the Peltier effect is the dominant role in the thermoelectric cooling process despite the opposite actions of the Joule and Fourier effects. The thermal resistance of TEC, which is Q2, decreases when the operating current (I) increases. For the different chip power, there is an optimum current (Iopt) making the interface thermal resistance between chip and TEC minimum (Q1). Q1can obtain the minimum 0.465°C·W-1 when the chip power is 25W and Iopt is 2.4A. The total thermal resistance (Qtotal) firstly decreases and then increases with the increase of operating current. There is an optimum current which allows the total thermal resistance is smallest. Qtotal may obtain the minimum value 0.672°C·W-1 when the chip power is 25W and Iopt is 2.4A. Furthermore, Qtotal Iopt both increase by the chip power.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

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