TY - JOUR

T1 - The single-blow transient test technique using pulse change inlet condition with optimized pulse width and matching time

AU - Wang, Hai-Xia

AU - Zhou, Guo-Yan

AU - Luo, Xing

AU - Kabelac, Stephan

AU - Tu, Shan-Tung

N1 - Funding Information: The authors are grateful for the financial support from the Higher Education Discipline Innovation Project (111 Project) under the funding code B13020. a ¯ \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{a} $$\end{document} Dimensionless pulse width A Total heat transfer surface area of test core, m 2 B Ratio of heat capacity of fluid in test core to that of solid wall c p,f Specific heat capacity of fluid at constant pressure, J/kgK c w Specific heat of solid material, J/kgK E Error amplification factor j Colburn j factor L Total length of test core, m m ˙ f \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\dot{m}}_{\mathrm{f}} $$\end{document} Mass flow rate of fluid, kg/s M f Mass of the fluid in the test core, kg M w Mass of the solid matrix of the test core, kg NTU Number of heat transfer units, dimensionless Re Reynolds number, the ratio of inertial forces to viscous forces, dimensionless T f Fluid temperature, K T f,max Maximum fluid temperature, K T 0 Initial fluid and solid material temperature, K T w Solid material temperature, K v fr Frontal free flow velocity of the air heater, m/s x Length coordinate, m x ¯ \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{x} $$\end{document} Dimensionless length variable, dimensionless

PY - 2020/3

Y1 - 2020/3

N2 - Compact heat exchanger is a kind of advanced heat transfer equipment with small size and high efficiency. It has wide application prospects in industry. However, due to the highly compact structure, it is difficult to measure the wall temperature of heat transfer surface by traditional test methods. For measuring the thermal performance of compact heat transfer surfaces more accurately, a single-blow transient test technique using pulse change inlet condition with optimized pulse width and matching time is developed. By turning on and off the electric air heater, the pulse change in the inlet temperature can be realized and is fitted as the superposition of a positive and a negative exponential function with a time shift. In order to reduce the effect of the uncertainty of temperature measurement, the optimum pulse width and optimum matching time is obtained by numerical calculations. By means of the newly extended test method, the heat transfer performance of a parallel-plate test core is measured and compared with the results from the literature. The analysis shows that the present pulse change technique considering the optimal pulse width and matching time have to be considered for the heat transfer surfaces with NTU > 4.5 to reduce the uncertainty in temperature measurement. The experimental results are in good agreement with those given in the literature.

AB - Compact heat exchanger is a kind of advanced heat transfer equipment with small size and high efficiency. It has wide application prospects in industry. However, due to the highly compact structure, it is difficult to measure the wall temperature of heat transfer surface by traditional test methods. For measuring the thermal performance of compact heat transfer surfaces more accurately, a single-blow transient test technique using pulse change inlet condition with optimized pulse width and matching time is developed. By turning on and off the electric air heater, the pulse change in the inlet temperature can be realized and is fitted as the superposition of a positive and a negative exponential function with a time shift. In order to reduce the effect of the uncertainty of temperature measurement, the optimum pulse width and optimum matching time is obtained by numerical calculations. By means of the newly extended test method, the heat transfer performance of a parallel-plate test core is measured and compared with the results from the literature. The analysis shows that the present pulse change technique considering the optimal pulse width and matching time have to be considered for the heat transfer surfaces with NTU > 4.5 to reduce the uncertainty in temperature measurement. The experimental results are in good agreement with those given in the literature.

UR - http://www.scopus.com/inward/record.url?scp=85074867175&partnerID=8YFLogxK

U2 - 10.1007/s00231-019-02745-4

DO - 10.1007/s00231-019-02745-4

M3 - Article

AN - SCOPUS:85074867175

VL - 56

SP - 963

EP - 972

JO - Heat and Mass Transfer

JF - Heat and Mass Transfer

SN - 0947-7411

IS - 3

ER -