Viscosity measurement of non-Newtonian fluids in pressure-driven flows of general geometries based on energy dissipation rate

Jang, Hye Kyeong,Hong, Sun Ok,Lee, Sang Bok,Kim, Ju Min,Hwang, Wook Ryol Elsevier Scientific Pub. Co 2019 Journal of non-Newtonian fluid mechanics Vol.274 No.-

<P><B>Abstract</B></P> <P>A novel viscosity measurement method is presented, which can be applied to the pressure-driven flow of an inelastic non-Newtonian fluid in an arbitrary geometry. The method is established on the balance of the energy dissipation rate such that the external power is dissipated within the system as viscous dissipation in a laminar regime in the absence of a body force. The effective viscosity can be expressed algebraically in terms of the pressure drop and flow rate and the corresponding effective shear rate is readily determined by flow rate; the relationship between effective viscosity and effective shear rate is found identical to the true material viscosity behavior. The two flow numbers, which depend on flow geometry only and are almost independent of fluid rheology, are involved: the coefficient of energy dissipation rate that associates the total energy dissipation rate to the Reynolds number; and the coefficient of effective shear rate, which relates flow rate to effective shear rate. After analytically validating the method for pressure-driven flow of a power-law fluid in a circular pipe, three different flows with complicated geometries were tested: numerical validations for axisymmetric expansion-contraction flows and flows in a Kenics mixer, and experimental validation for flows in a complex microfluidic array with Xanthan gum solutions. Errors in viscosity were less than 2.9% and 16% in simulations and in experiments, respectively. The method is well-suited for on-line monitoring of <I>in-situ</I> viscosity for non-Newtonian fluid flow in industrial processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An energy dissipation-based viscosity measurement technique is proposed. </LI> <LI> Only two flow numbers are employed for viscosity measurement of inelastic fluids. </LI> <LI> The method is applicable to <I>in-situ</I> viscosity monitoring of non-Newtonian fluids. </LI> </UL> </P>

건식 3채널 초음파 유량측정 방법에 대한 연구

전세종(Sejong Chun),윤병로(Byung-Ro Yoon),강웅(Woong Kang),권휴상(Hyu-Sang Kwon) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, the clamp-on ultrasonic flow metering indicates flow rates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow metering amounts as low as ±1 % if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be greater than ±2 % if the flow velocity is lowered smaller than 0.5 m/s. These shortcomings of the clamp-on ultrasonic flow metering can be overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is named as combined V/Z clamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performance between the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths.

돈사 환기량 측정용 풍량 측정 장치 길이에 따른 환기량 비교

황옥화,죠슈아 나이젤 할더,박준수 (사)한국축산환경학회 2023 한국축산시설환경학회지 Vol.25 No.2

The length of air flow measurement device for measuring the ventilation rate from a pig barn is an factor that affects the estimation of ventilation rate. This study focused on ventilation rate comparison according to the length of air flow measurement device of hood-type. The pig barns (5 m × 8 m × 7 m) was installed an mechanically forced exhaust fan of chimney-type. The ventilation rate respectively was evaluated on 1) the device of length by a long (5 parts duct) or short (3 parts duct) and 2) whether the device was installed or not to a exhaust fan. At this time, there were also conducted in the condition of the presence or absence of a honeycomb duct, which was the last phase of the device. Both experiments were tested according to the operating rate of the exhaust fan (30, 50, 70, and 100%). The ventilation rate were lower in the long-length device than in the short-length from both experiments. In experiment 2, the reduction rate of ventilation rate compared with non-installed was higher in the long-length device than in the short-length. In conclusion, the findings confirmed that long-length device was caused the underestimate of ventilation rate.

에너지 소산 기반 유동정량화 기법을 이용한 모델 금형 내 비뉴턴 유체의 점도 모니터링

이선호(Sun Ho Lee),조해진(Hae Jin Jo),이종욱(Jong Wook Lee),황욱렬(Wook Ryol Hwang) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.1

사출 공정의 점도 모니터링은 공정 조건 설정의 핵심요소이다. 사출 공정의 특성상 금형의 형상은 매우 다양하며 용융 고분자와 같은 비뉴턴 유체의 경우 각 위치에서의 전단율과 점도가 다르게 나타난다. 따라서 연속적 유동을 대표할 수 있는 유효 점도를 측정할 필요가 있으나 금형의 복잡한 형상으로 인해 일반적인 벽면응력 기반의 기법을 이용하여 점도를 측정하기 어렵다. 본 연구에서는 에너지 소산기반의 유동정량화 기법을 적용하여 모델 금형 내 비뉴턴 유체의 유효 점도를 측정하였으며, 측정은 유량과 압력 강하를 포함한 간단한 대수적 계산을 통해 이루어졌다. 복잡한 형상에서의 실험을 통한 점도 예측 결과는 기존 유체의 점도 측정 데이터와 32.6% 내에서 일치하였다. Viscosity is a key factor in process control for the injection molding process, in which the mold shapes are often complex and fluids (polymer melts) are highly non-Newtonian that leads to diverse distributions of the shear rate and viscosity within the mold. In the present study, we propose a method to effectively measure viscosity corresponding to the shear rate that represents the average shear rate of the flow. An energy dissipation-based flow quantification was used to measure the effective viscosity and effective shear rate of a non-Newtonian fluid inside a modeled mold. The measurement was made through flow rate and pressure drop in both numerical and experimental methods. The viscosity measured using the proposed method was found to be consistent with rheological data which was within 32.6% errors.

압축성유체 유량계측장치 설계 및 제작

지상원(S. W. Ji),장지성(J. S. Jang) 유공압건설기계학회 2013 드라이브·컨트롤 Vol.10 No.4

Pneumatic system is widely applied in various industry because it have a many advantage(low cost, high safety, etc..). For design of pneumatic system, accurate flow measurement is required. In this study, compressible fluid flow measurement apparatus was designed and built. It uses an isothermal chamber that can approximate isothermal condition. Therefore, it can be measured for flow-rate using pressure response of isothermal chamber. As a result, this apparatus can be measured for sonic conductance and critical pressure ratio of pneumatic components and it required less time and energy than conventional flow meter. The effectiveness of the designed apparatus is proved by experimental result.

아시아 4개국의 국제자본 통제정책을 고려한 새 외환시장 압력지수에 관한 연구*

서재현 한국무역연구원 2023 무역연구 Vol.19 No.5

Purpose – An exchange market pressure index (EMP) exhibits not only exchange-rate fluctuations but also the changes of government tools to manage exchange rates. Therefore, it is useful to estimate hidden pressures that exist in foreign exchange markets. This study suggests a new EMP that might have more information on foreign exchange markets than other indices. Design/Methodology/Approach – We include a capital-flow management (CFM) measure as another component in our new EMP to consider the role of CFMs for managing exchange rates. This new index is then applied to the four Asian countries of South Korea, Malaysia, Philippines, and Japan to analyze their foreign exchange markets. Findings – We found that the new EMP sends stronger signals before and during the currency crises than existing indices. Moreover, the volatility of emerging market EMP is stronger than that of advanced countries because the former group changes CFM policies more frequently than the latter . These findings suggest that the new EMP might describe exchange rates and pressures in foreign exchange markets better than other indices. Research Implications – To our best knowledge, this study is one of few attempts to incorporate CFM measures into an EMP to consider the effectiveness of CFMs in managing exchange rates.

엔진고공시험에서의 엔진 입구 덕트용 공기 유량 측정 장치의 특성 분석

강웅,최해만,최용문,김용규,김춘택 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

가변형 임계노즐 유동에 관한 수치해석적 연구

이준희(Jun-Hee Lee),김희동(Heuy-Dong Kim),박경암(Kyung-Am Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

For the critical nozzle operating in a wide range of flow conditions, the nozzle throat diameter should be changed depending on the amount of the mass flow rate. A cone-type movable cylinder which is inserted into the conventional critical nozzle can be used to obtain the variable operations by changing the effective cross-sectional area at the nozzle throat. In the present study, the effectiveness of the variable critical nozzle is investigated. A computational work is carried out using the 2-dimensional, axisymmetric, compressible Navier-Stokes equations which are discretized using a fully implicit finite volume method. The angle of the cone-cylinder and its location are varied in wide range of the critical nozzle operation pressures. The present computational results predict the measured mass flow rates.

Experimental verification of a virtual water flowmeter applicable to air conditioning systems

Kim, M.H.,Jeong, J.W. Elsevier Sequoia S.A 2017 Energy and buildings Vol.155 No.-

The main purpose of this research is to suggest a virtual water flowmeter applicable in hydraulic systems with low-cost sensors. Practical procedures for realizing virtual water flowmeters for constant flow pumps (i.e., Cases 1 and 2) and variable flow pumps (i.e., Cases 3 and 4) are proposed in this paper. In Case 1, for measuring the water flow rate through a constant flow pump, the pump head was measured and the water flow rate was estimated using the pump characteristic curve obtained from the manufacturer or by deriving an empirical model based on the field measurement data. In Case 2, the water flow rate through a valve with a constant flow pump was estimated by measuring the pressure head between the valve and the valve opening position. The valve characteristic curve can be obtained by deriving an empirical model based on the initial field test results. The water flow rate through the variable flow pump was calculated, using the pump affinity laws and an empirical model, by measuring the frequency (i.e., Case 3) or input power (i.e., Case 4). The initial setup and test procedures for virtual flowmeters are also proposed in this research for practical use in the field. To verify the proposed procedures, experiments were conducted using constant and variable flow pumps in a pilot system. It was found that the virtual water flowmeters showed 2.9% to 6.7% of root mean square error from Case 1 to Case 4, compared with an ultrasonic water flowmeter, through long-term experimental verification.

남강댐 주요지점에서의 수위-유량곡선식 불확실도 평가

장대정 청운대학교 건설환경연구소 2013 청운대학교 건설환경연구소 논문집 Vol.8 No.2

Rating curve is a graph of discharge versus stage for a given point on a stream. For the reliable hydrological data acquisition, the improvements of flow measurement technique are desirable with the quantitative analysis of uncertainty with profound discussion. Uncertainty was computed using random uncertainty, systematic uncertainty and total uncertainty in condition that low flow during dry season. Likewise, it was given careful consideration to the uncertainty of relation rating curve equation and standard error from measurement flow when the rating curve equation was developed by the major site stage-discharge data during flood season. 수위-유량곡선은 하천의 임의 점에서 수위와 유량의 그래프이다. 신뢰성 있는 수문학적 자료의 취득을 위한 유량관측 기법의 개선은 불확실도의 정성적인 해석을 요구하고 있다. 평·갈수 조건에서 불확실도는 무작위 불확실도, 계통 불확실도 그리고 총 불확실도를 사용하여 평가하고 있다. 또한 홍수기 동안 주요 관측소에서 관측된 수위-유량자료에 의해 생성된 수위-유량곡선식의 표준편차와 수위-유량곡선식의 관계에 의하여 불확실도를 평가하고자 한다.