mod_eprivacy

High resolution measurements of heat transfer during drop impingement onto a heated wall with particularly consideration of evaporation at the 3-phase contact line

Description

The droplet impact on a hot surface plays an important role in a variety of applications, such as coating processes, spray cooling processes of turbine blades, quenching processes during metal hardening, cooling of metal rolling mills and lasers and in the combustion of fuels in Otto and diesel engines or in combustion chambers of turbines. If the surface temperature is above the saturation temperature of the liquid and below the Leidenfrost temperature, the heat transfer into the droplet depends on the droplet hydrodynamics and the heat and mass transport in the area of three-phase contact line. Despite extensive numerical and experimental investigations, the knowledge of the dynamic processes of the heat and mass transport in this area is still insufficient. In order to be able to develop detailed models for the simulation of hydrodynamics and heat transport processes during the droplet impact, experimental investigations of the three-phase contact line (single meniscus experiment) must be carried out using high-resolution surveying techniques, in addition to droplet impact experiment. Based on this background, this project completes a parallel project (TP-C1), in which the theoretical foundations and a numerical model of the process are developed.

One of the focuses in the first and second funding periods was on evaporation at a single meniscus. The influence of system pressure, the contact line velocity and its direction and the nano-textured heater surfaces on the heat transfer in the direct vicinity of the three-phase contact line has been experimentally investigated. It has been revealed that the heat flux close to the three-phase contact line decreases with increasing pressure. This behavior scales well with the decrease of liquid latent heat of evaporation. Concerning the heat transfer at advancing and receding contact lines, it has been found that as long as the heat transfer is dominated by contact line evaporation, the heat flux peak at receding contact lines is smaller than that of advancing contact lines. While the heat flux peak (and thereby the overall heat transfer close to the contact line) increases with velocity at an advancing contact line, it has been found to be independent from the contact line velocity at receding contact lines. Additionally, it has been observed that receding meniscus of high velocities leaves behind an evaporation liquid film. Using nano-textured heater surfaces leads to increase of the local heat flux in the vicinity of the three-phase contact line by approximately 60%. In this case, the evaporating thin film has been observed even at low receding velocities, which leads to higher evaporation rate and consequently, heat transfer enhancement.

Hydrodynamics, heat transport and evaporation during a single droplet impacting on a heated wall have been studied experimentally. The experiments have been performed with FC-72 at atmospheric pressure and saturation conditions. The results show an extremely high heat fluxes directly after impact due to the high temperature difference between the wall and the droplet. At the end of the droplet receding phase the heat transfer in the droplet was dominated by evaporation in the vicinity of the three-phase contact line.

It is planned to examine the effect of the system pressure, micro- and nanostructured heater surfaces and fluid composition on the heat and mass transfer during the droplet impact. The knowledge gained from first and second project phases with respect to the dynamics as well as heat and mass transport in the area of the three-phase contact line together with the dynamics of an individual droplet impact form an indispensable basis for the description of the coalescence of several droplets impacting a hot surface. Experimental investigation of the influence of the droplet coalescence, the micro- and nanostructured surfaces and surface wettability on the heat transport during several droplet impacts is the main aim of the third project phase.

Team

Apl. Prof. Dr. Sc. Tatiana Gambaryan-Roisman

Apl. Prof. Dr. Sc. Tatiana Gambaryan-Roisman

Director subarea C1/C2 This email address is being protected from spambots. You need JavaScript enabled to view it. +49 6151 16-22264
Prof. Dr.-Ing. Peter Stephan

Prof. Dr.-Ing. Peter Stephan

Director subarea C1/C2 This email address is being protected from spambots. You need JavaScript enabled to view it. +49 6151 16-22260
Alireza Gholijani, M.Sc.

Alireza Gholijani, M.Sc.

C2 This email address is being protected from spambots. You need JavaScript enabled to view it. +49 6151 16-22270
140141142

Publications

2017

S. Fischer, R.P. Sahu, S. Sinha-Ray, A.L. Yarin, T. Gambaryan-Roisman, P. Stephan:
Effect of nano-textured heater surfaces on evaporation at a single meniscus.
International Journal of Heat and Mass Transfer, Vol. 108, pp. 2444-2450, 2017.

2016

Batzdorf, S., Breitenbach, J., Schlawitschek, C., Roisman, I. V., Tropea, C.,Stephan, P., and Gambaryan-Roisman, T.:
Heat transfer during multiple drop impacts onto a hot solid substrate.
Int. J. Heat Mass Transf. (under revision 2016)

Freystein, M., Kolberg, F., Spiegel, L., Sinha-Ray, S., Sahu, R.P., Yarin,, A. L., Gambaryan-Roisman, T., Stephan P. 2016,
Trains of Taylor bubbles over hot nano-textured mini-channel surface
Int. J. Heat Mass Transf., v. 93, pp. 827-833, doi:10.1016/j.ijheatmasstransfer.2015.10.054>

2015

Fischer, S., Gambaryan-Roisman, T., Stephan, P. 2015,
On the development of a thin evaporating liquid film at a receding liquid/vapour-interface
Int. J. Heat Mass Transfer, v. 88, pp. 346-356, doi:10.1016/j.ijheatmasstransfer.2015.04.055

S. Fischer:
Experimental Investigation of Heat Transfer during Evaporation in the Vicinity of Moving Three-Phase Contact Lines.
PhD thesis, TU Darmstadt, 2015.

2014

Fischer, S., Batzdorf, S., Gambaryan-Roisman, T., Stephan, P.,
High resolution heat transfer measurements at the three phase contact line of a moving single meniscus
Proceedings of the 15th International Heat Transfer Conference, IHTC15-8230, August 10-15, 2014, Kyoto, Japan

Gambaryan-Roisman, T.,
Controlling hydrodynamics, heat transfer and phase change in thin liquid films and drops
Keynote Lecture at the 15th International Heat Transfer Conference, August 10-15, 2014, Kyoto, Japan, doi:10.1615/IHTC15.kn.000001>

2013

Herbert, S., Fischer, S., Stephan, P., Gambaryan-Roisman, T.
Local heat transfer and phase change phenomena during single drop impingement on a hot surface
Int. J. Heat Mass Transfer 61 (2013), 605-614

2012

Fischer, S. Herbert, S., Sielaff, A., Slomski, E. M., Stephan, P., Oechsner, M.
Experimental investigation of nucleate boiling on a thermal capacitive heater under variable gravity conditions
Micro- gravity Science and Technology 24 (2012), 139–146

Kunkelmann, C., Ibrahem, K., Schweizer, N., Herbert, S., Stephan, P., Gambaryan-Roisman., T.
The effect of three-phase contact line speed on local evaporative heat transfer: Experimental and numerical investigations
Int. J. Heat Mass Transfer 55 (2012), 1896-1904

Fischer, S. Herbert, S., Slomski, E. M., Stephan, P., Oechsner, M.
Local heat flux investigation during pool boiling single bubble cycles under reduced gravity
Proceedings 8th Int. Conference on Boiling and Condensation Heat Transfer, Lausanne, Schweiz, Juni 2012

Herbert, S., Fischer, S., Stephan, P., Gambaryan-Roisman, T.
Untersuchung des Wärmeübergangs beim Einzeltropfenaufprall auf beheizte Wände – Simulation und Experiment. Tagung des Fachgruppe Wärme- und Stoffübertragung
ProcessNet VDI/ Dechema, Weimar, 2012

Herbert, S., Fischer, S., Gambaryan-Roisman, T., Stephan, P.
Local heat transfer and phase change phenomena during single drop impingement on a hot surface
Extended Abstract, Proceedings 6th Europ. Thermal Science Conference (Eurotherm 2012), Poitier, 2012

2010

Ibrahem, K., Abd Rabbo, M.F., Gambaryan-Roismann, T., Stephan, P.
Experimental investigation of evaporative heat transfer characteristics at the 3-phase contact line
Experimental Thermal and Fluid Science 34 (2010), 1036-1041

Ibrahem, K., Abd Rabbo, M.F., Gambaryan-Roismann, T., Stephan, P.
Experimental investigation of micro-scale heat transfer at an evaporating moving the 3-phase contact line
Proceedings 14th Int. Heat Transfer Conference, IHTC14-22280, Washington DC, USA, August 2010

Ibrahem, K., Abd Rabbo, M.F., Gambaryan-Roismann, T., Stephan, P.
Experimental and numerical investigation of evaporative heat transfer in the vicinity of the 3-phase contact line
Proceedings Conference on Thermal Issues in Emerging Technologies ThETA 3, Cairo, Ägypten, Dezember 2010

Sunday, August 25, 2019