A new approach to define of the thermal parameters, such as heat capacity and through-plane thermal conductivity, of pouch-type cells is introduced. Application of local heat flux measurement with a ...gradient heat flux sensor (GHFS) allows determination of the cell thermal parameters in different surface points of the cell. The suggested method is not cell destructive as it does not require deep discharge of the cell or application of any charge/discharge cycles during the measurements of the thermal parameters of the cell. The complete procedure is demonstrated on a high-power lithium-ion (Li-ion) pouch cell, and it is verified on a sample with well-known thermal parameters. A comparison of the experimental results with conventional thermal characterization methods shows an acceptably low error. The dependence of the cell thermal parameters on the state of charge (SoC) and measurement points on the surface was studied by the proposed measurement approach.
The gradient heat flux sensor made of a bismuth single crystal is calibrated. The volt–watt sensitivity of the sensor is determined and the method of data processing based on the 1D heat conduction ...equation for a thin plate is proposed. This method is tested on experimental data obtained for the initiation of a laser discharge in a calm atmosphere and in a supersonic gas flow.
The popularity of lithium-ion (Li-ion) batteries has increased over the recent years. Because of the strong dependence of the Li-ion battery operation characteristics on temperature, heat generation ...in the battery has to be taken into account. The entropy change of a Li-ion battery has a significant influence on heat generation, especially at a low C-rate current. Therefore, it is necessary to consider the entropy change profile in the estimation of heat generation. In the paper, a method to determine the entropy change (ΔS) profile by heat flux measurements of a cylindrical Li-ion cell is proposed. The method allows simultaneous measurements of the thermal diffusivity and ΔS of the cylindrical cell. The thermal diffusivity and ΔS measurements are carried out by a gradient heat flux sensor (GHFS). The comparison between the ΔS profile determined by the GHFS method with that obtained using a standard potentiometric method clearly shows that the entropy change measurements could be made by using a GHFS. Even though the uncertainty of the reported method is higher than that of the potentiometric method, a significant decrease in the experiment time compared with the potentiometric method is a major advantage of this method.
•ΔS measurements by using a gradient heat flux sensor are presented.•Time required for the ΔS measurements by the potentiometric method is evaluated.•Uncertainty and limitations of the methods under consideration are given.•Comparison of the proposed method with the potentiometric method is made.
"Thermophysics of Power Units" Department is based on pre-existed "Thermodynamics and Heat Transfer" and "Reactors and Boilers" Departments. The main goal of the new department (in addition to ...training students in basic courses of Thermodynamics, Heat and Mass Transfer, Fluid Mechanics, Metrology and Thermal Measurement) has become a new master's profile "Thermal Engineering, Energy Audit and Energy Service". It required radical restructuring of the whole educational process, and in the first place - its material resources and equipment. Over the last two years "Heat and Mass Transfer" lab and "Wind tunnel" lab are upgraded, and "Metrology and Thermophysical Measurement" lab is newly created. Tutorials of new generation are changing significantly the structure of our main courses. The members of our scientific group (2 - 6 year students) actively engaged in the work process. Now we hope to see the best of them among our future postgraduates.
The usage of gradient heat flux measurement for monitoring of heat flux on combustion chamber surface and optimization of diesel work process is proposed. Heterogeneous gradient heat flux sensors can ...be used at various regimes for an appreciable length of time. Fuel injection timing is set by the position of the maximum point on the angular heat flux diagram however, the value itself of the heat flux may not be considered. The development of such an approach can be productive for remote monitoring of work process in the cylinders of high-power marine engines.
Abstract
In the study of heat transfer during boiling, optical methods and thermometry are prevailing. The possibilities of experiment are significantly expanded by new technology – gradient ...heatmetry, in which heterogeneous gradient heat flux sensors with time constant of nanoseconds are used. When studying of boiling of subcooled water in a large volume on the surface of the titanium sphere, preheated up to 300-500 °C, heatmetry was combined with visualization of boiling modes using a high-speed camera Evercam 1000-4-M. It is possible to obtain the distribution of heat flux per unit area along the latitudinal coordinate and to relate the local heat flux per unit area with observed boiling regimes and initial temperatures of water and the model.
The aim of the study is to determine optimum tilt of the pipe at film condensation by using of gradient heatmetry. Dependence of heat flux per unit area on time and azimuthal angle are presented for ...vertical, horizontal and inclined pipe. Maximal heat transfer coefficients for experimental conditions are observed for the angle 20° from vertical. The gradient heatmetry gives high informational content, which opens up new possibilities for studies of heat transfer during condensation.
Heat transfer during condensation of saturated water steam on the outer surface of a pipe has been investigated by the method of gradient heat flux measurement. Heat flux per unit area and heat ...transfer coefficients obtained for vertical, horizontal and inclined pipe are presented. The optimum angle of inclination of the pipe (ψ = 30 °) was experimentally determined. High informational content of gradient heat flux measurement has been revealed, which opens up new possibilities for studies of heat transfer during condensation.
Gradient heat flux measurement (gradient heatmetry) is a modern technology for measuring heat flux per unit area using gradient-type sensors. Since 2015, gradient heatmetry has been used to study ...heat transfer in film condensation of saturated steam on the inner and outer surface of tubes. This measurement method offers greater information capabilities than the more widely used thermometry when the heat flux is calculated from the temperature measured with thermocouples. The advantage of gradient heatmetry results from abnormally fast response time of sensors which is about 10
–8
–10
–9
s. Therefore, they may be considered almost inertia-less measuring devices. Direct measurement of heat flux per unit area reduces the total uncertainty in calculating local and average heat-transfer coefficients. Heat transfer in film condensation of saturated steam on the outer and inner surfaces of tubes was studied using gradient heatmetry. Gradient heat flux sensors (GHFS) made of single-crystal bismuth were used on the outer surface, while heterogeneous GHFSs made of Grade 12Kh18N9T steel + Ni composition were installed on the inner surface. In both cases, reference tests were performed on vertical tubes. Their results confirmed the excellent information capability of this approach and its applicability for estimating heat flux. A series of experiments was carried out to study heat transfer during film condensation of saturated steam on the outer and inner surfaces of inclined pipes. The highest heat-transfer coefficient of 6.94 kW/(m
2
K) in condensation of saturated steam on the outer surface of a tube is observed for the tube inclined at an angle of 20° to the vertical. This value exceeds the heat-transfer coefficient on a vertical tube by 14.9%. The highest heat-transfer rate in condensation on the inner surface was observed for the tube inclined at 60° to the vertical.
Abstract
This paper presents experimental study of heat transfer during film condensation of saturated water steam on the outer surface of the inclined pipe by gradient heatmetry. Heat flux per unit ...area was measured by gradient heat flux sensors made of a single-crystal bismuth. The experimental results are presented in the graphs of heat flux per unit area dependence on time and azimuthal angle. The highest average heat transfer coefficient during condensation of α = 6.94 kW/(m
2
• K) was observed when the pipe was inclined at the angle of ψ = 20 °. This value exceeds one obtained on a vertical pipe by 14.9 %. Heat transfer enhancement during condensation of saturated water steam on inclined pipe is associated with changes in condensate film flow. Another part of experiments was made by simultaneously using of gradient heatmetry and condensate flow visualization. Experimental results confirmed the applicability and high informative content of proposed comprehensive method. Comprehensive study of heat transfer during condensation confirmed that heat flux per unit area pulsations may be explained by the formation of individual drops, their coalescence, and drainage from the sensor surface.
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