로봇 냉각을 위한 수냉식 냉각판의 성능 평가

이석원(Suk Won Lee),강상우(Sarng Woo Karng),황규대(Kyudae Hwang),김서영(Seo Young Kim),리광훈(Gwang Hoon Rhee) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.3

The increase of system weight due to installation of cooling devices adds electrical and mechanical loads of humanoid robot, and in return, results in much heat. Therefore, the weight of cooling system is a critical issue for robot cooling. In this study, we propose non-metallic cold plates to deal with such problems. We compare thermal performances between one metallic cold plate and five different types of non-metallic cold plates. A metallic cold plate is totally made of copper. Five non-metallic PC (polycarbonate) cold plates, which are designed to reduce the overall weight of robot cooling system, are composed of a polycarbonate cover with different types of base plate. The overall heat transfer coefficients per unit mass and thermal resistances are obtained for the cold plates. The metallic cold plate shows the best thermal performance. It is interesting to note that the PC cold plate with an aluminum base plate with 18 channels shows the best overall heat transfer coefficient per unit mass. Most polycarbonate cold plates display fairly comparable thermal performance with more reduced system weight compared to the metallic cold plate.

로봇 냉각을 위한 비금속 재질의 이상 냉각판에 대한 열전달 특성

강상우(Sarng Woo Karng),이석원(Suk Won Lee),황규대(Kyudae Hwang),김서영(Seo Young Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

It was investigated to compare thermal performances among a metallic cold plate and a non-metallic cold plate by using dielectric fluid (FC-72) as the working fluid in two-phase circulation. Two types of cold plates have the same dimension of 36×30 ㎟ base area with 7 ㎜ high. A metallic cold plate was totally made of copper. A polycarbonate (PC) cold plate, which was designed to reduce the overall weight of robot cooling system, was composed of a PC cover with copper base plate. Two types of cold plates were mounted on a 20×20 ㎟ copper heating block of 30 W/㎠. It was found that PC cold plate showed better thermal performance than the copper cold plate in terms of thermal resistance with considering unit mass. Furthermore, it was known that the two-phase PC cold plate with a copper base can be an effective cooling device for humanoid robots due to keeping below 70℃ of the surface temperature of the heating block at the input power of 10 W/㎠.

Numerical analysis of LiFePo4 battery thermal management system using cold plate

Seyeon Hwang,Rakjun Choi,김설하,Minjae Song,김태주 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Lithium-ion batteries are widely used in electric vehicles because of their high capacity and voltage. However, some drawbacks to the battery stability exist. The aim of our research was to determine the optimum width and number of channels of a cold plate. To estimate the temperature distribution and heat transfer rate, the MSMD (multi-scale multidimensional) - Newman P2D model in ANSYS Fluent was used. Prior to comparing the heat transfer rates of the various battery surfaces using different cold plates, the surface temperature of the battery (LiFePO4) at discharge rates of 2C, 3C, and 4C was calculated to determine the battery characteristics. Subsequently, two cold plates were attached to both sides (front and back) of the batteries and the heat transfer rate of the battery surface in contact with the cold plate, and the pressure drop between the inlet and outlet of the channels during the discharge process were estimated. In addition, the j and f factors, which are used to estimate the cooling performance of the cold plates, were calculated. In determining the most efficient cold plate options, the trade-off between the heat transfer coefficient and the pressure drop is also important for the relationship between the two factors (j and f factors).

Cold plate를 이용한 휴대용 컴퓨터 냉각 시스템의 열성능에 관한 연구

박상희(Sang-Hee Park),조남해(Nam-Hea Cho),최성대(Sung-Dae Choi) 한국기계가공학회 2009 한국기계가공학회지 Vol.8 No.4

This study investigates two-phase cooling system of close-loop by using FC-72 and PCM(Phase change material). The cooling system consists of evaporator, cold plate, micro pump, and condenser. The heat input on the performance of evaporator is appreciated by visualizing the boiling on the evaporator. The heat performance of cooling system is investigated to determine the effects of volume fill ratio change at working fluid, pump flow rate change, and volume fill ratio change at PCM in cold plate. Experimental results show the ideal condition when the volume ratio of working fluid, the pump flowing, and the volume ratio of PCM are 60%, 6ml/min, and 60% respectively.

Experimental and Numerical Study on the Eff ect of Heel Plate Length and Thickness on the Structural Integrity of Cold-formed Steel Roof Trusses

Je Chenn Gan,Jee Hock Lim,Siong Kang Lim,Horng Sheng Lin 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.1

Cold-Formed Steel (CFS) is widely used as secondary framing material. Nowadays, the research of CFS as a primary steel roof truss system became more favoured. Therefore, it is very important to understand the behaviour of CFS roof trusses due to the uncertainty of the confi guration of CFS roof trusses can aff ect its structural integrity. The objective of this research is to investigate the eff ect of heel plate length and thickness to the ultimate load capacity of CFS roof truss system. Nine diff erent lengths and thicknesses of heel plate specimens were fabricated and subjected to concentrated loads until failure. The highest ultimate capacity for the experiment was 28 kN. Local buckling of top chords adjacent to the heel plate was the primary failure mode for all the heel plate. The results showed that the increment of the length and thickness of the heel plate had slightly increased the ultimate capacity, but decrease the defl ection. The behaviour of the numerical results showed a good agreement with the experimental results. Numerical load capacity was higher than experimental load by an average ratio of 1.12. The behaviour of the bottom chord for both results was diff erent after the load reached 20 kN.

Numerical Analysis and Experimental Investigation on Behavior of Cold-Formed Steel Castellated Beam with Diamond Castellation

S. Prabhakaran,S. A. Maboob 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.3

The main purpose of the current research work is to achieve an economical cold formed steel castellated beam with diamond castellation with limited buckling. In this way, to study the behavior of cold formed steel castellated beam with diamond castellation by the provision of diff erent methods of placing the stiff eners for the sections is an main scope of the work. It can be achieved through this paper, which gives an Numerical, Analytical Study and Experimental investigation on the performance of cold-formed steel Castellated beams with Diamond Castellation shape. Perforations in web has been carried out to know its structural behaviour as simply supported beam under pure bending. The castellated steel beams with perforated web epitomize a new inventive which has occurred in the past span for the short- and medium length of beams. The Cold- Formed Steel provides a substantial weight reduction of these beams with castellation, compared to the hot-rolled beams. The Castellated Beam has made with 2 mm thickness CFS Steel, used all over the Beam. In the study, the Castellated Beam has been performed with three types of Stiff ener Designs at web of the Beam. Beam with intercept Stiff eners plates at web has used. Both stiff ened and unstiff ened Castellated beam (Beam with Parallel, Perpendicular and intercept Stiff eners) were tested for numerical and experimental Testings. Finally, numerical analysis using ABAQUS 6.11 results are evaluated and the experimental results were confi rmed with the results obtained from the fi nite element analysis. Based up on the numerical analysis and experimental investigation the diff erent failure and buckling modes of the proposed beams has been studied and the load carrying capacity of beams has been predicted.

Numerical study on the rotation capacity of CFRP strengthened cold formed steel beams

Mohammed H. Serror,Essam G. Soliman,Ahmed F. Hassan 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.4

Currently, CFRP (Carbon Fiber Reinforced Polymer) plate bonding is used quite extensively as a strengthening method. In this technique, a composite CFRP plate or sheet of relatively small thickness is bonded with an adhesion material to steel or concrete structure in order to improve its structural behavior and strength. The sheets or plates do not require much space and give a composite action between the adherents. In this study, the rotation capacity of CFRP-strengthened cold-formed steel (CFS) beams has been evaluated through numerical investigation. Studies on different structural levels have been performed. At the beam level, C-section has been adopted with different values of profile thickness, web height, and flange width. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web-bolted connections without CFRP strengthening, premature web buckling results in early loss of strength. Hence, CFRP sheets and plates with different mechanical properties and geometric configurations have been examined to delay web and flange buckling and to produce relatively high moment strength and rotation capacity. The numerical results reveal that CFRP strengthening may increase strength, initial stiffness, and rotation capacity when compared with the case without strengthening.

Modeling of wind-induced fatigue of cold-formed steel sheet panels

Osvaldo Rosario-Galanes,Luis A. Godoy 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.2

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in acompanion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

Modeling of wind-induced fatigue of cold-formed steel sheet panels

Rosario-Galanes, Osvaldo,Godoy, Luis A. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.2

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in a companion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

Electrical and thermal transport properties of vanadium oxide thin films on metallic bipolar plates for fuel cell applications

Jung, H.M.,Um, S. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.26

We have focused on the in-depth comparative evaluation of the suitability of electrically-induced thermal transport characteristics of highly disordered vanadium oxide thin films deposited onto metallic bipolar plates as an expeditious self-heating source for the successful cold-start of fuel cells in a subfreezing environment. To achieve this, sol-gel derived vanadium oxide thin films on the non-polished surface of 316L austenitic and 446M ferritic substrates have been fabricated by a dip-coating process. The effects of electrical properties on thermal energy dissipation rate of the as-synthesized thin films deposited onto 316L and 446M stainless steel plates were firstly investigated and compared with each other. Subsequently, a series of physical, chemical, and structural analyses of the thin films have been performed using several analytical techniques such as the ASTM D3359, the ASTM D5946, XPS, and FE-SEM. The most important finding of this study was that the electrical resistivity of the thin films on 446M ferritic substrate was extremely low on a level of 4.8% of the 316L sample at -20 <SUP>o</SUP>C, and then the surface temperature rise of the thin film on 316L austenitic substrates was approximately 21.8 times greater than that of 446M ferritic substrates under simulated cold starting conditions (i.e., at a current density of 0.1 A.cm<SUP>-2</SUP> at -20 <SUP>o</SUP>C). Therefore, we concluded that vanadium oxide thin films on 316L austenitic stainless steel plates appears to be more applicable than those of 446M ferritic substrates for the cold-start enhancement of fuel cells from the practical point of view.