Thesis supervisor: Tibor Poós
Location of studies (in Hungarian): BME Department of Building Services and Process Engineering Abbreviation of location of studies: ÉPGET
Description of the research topic:
a.) Preliminaries:
Evaporation is influenced by gas and liquid conditions and properties; the amount of evaporated liquid depends on these parameters. According to these parameters, different evaporation cases can be defined for the evaporation of liquids with open surface under natural, mixed and forced convection. Based on the literature correlations and results, it was determined with the help of dimensional analysis which dimensionless numbers and equations can be used to describe the phenomenon of evaporation. The variables of the dimensionless equations were determined empirically, for which both literature and own measurement results were used. In this way, two dimensionless equations were created that describe the evaporation of water in the case of natural or mixed and forced convection under constant gas and liquid conditions. However, the use of these equations runs into limitations, which are set by the validity ranges of the equations.
Many international journal articles and conference articles have been published on the topic, and project assignments, BSc theses and MSc theses have been prepared.
b.) Aim of research:
The aim of the research is to investigate the evaporation rate of liquids and the simultaneous heat and mass transfer empirically and with the help of simulations. With the development of a laboratory measuring device suitable for measuring the evaporation rate, evaporation can be tested at different air temperatures, air velocities, air humidities and liquid temperatures, as well as in the case of liquids other than water. Based on the own measurement results and those from the literature, a correlation can be created that can describe the evaporation in the case of natural, mixed and forced convection under constant gas and liquid conditions. Simulation software can be used to model the process of evaporation in the case of constant gas and liquid conditions (base case), and the results of the model can be validated with the measurement results. If the description of the basic processes provides satisfactory results, it can serve as the basis for the description of evaporation cases under time- and locally-varying gas and liquid conditions.
c.) Tasks, main items, necessary time:
• Collection and study of literature data on the simultaneous heat and mass transfer of liquids, as well as numerical models describing the phenomenon (1 semester).
• Development of laboratory equipment, with the help of which during the examination of the evaporation of the heated/unheated liquid, in addition to the temperature and velocity of the air, the humidity can also be controlled. Carrying out laboratory measurements to determine the evaporation rate with different air and liquid conditions and liquid level (2 semesters).
• Exploring the relationships between necessary material characteristics, operating parameters and heat and mass transfer mechanisms, determining the initial and boundary conditions of the numerical model with constant and changing gas and liquid conditions (1 semester).
• Creating a numerical model of the operation, performing the necessary calculations to validate the simulation results (2 semesters).
• Publishing the results in scientific journals and preparing the PhD thesis (2 semesters).
d.) Required equipment:
• Laboratory measuring equipment suitable for determining evaporation rate.
• Instruments and sensors capable of measuring various operating parameters, as well as data collection and data collection software for automatic recording of measured data.
• IT hardware and software background to carry out the research work.
The listed equipment are provided to start the research.
e.) Expected scientific results:
• Laboratory measuring device suitable for testing the rate of evaporation at different air temperatures, air velocities, air humidities and liquid temperatures.
• Correlations suitable for determining the evaporation rate for describing evaporation with constant gas and liquid conditions in the case of different liquids.
• Development of a numerical model to describe evaporation in the case of evaporation with constant or variable gas and liquid conditions.
• The effect of parameters on the evaporation rate.
f.) References:
[1] Varju, E.; Poós, T.: New dimensionless correlation for mass transfer at evaporation of open liquid surface in natural convection. International Communications in Heat and Mass Transfer 136, 2022. DOI: 10.1016/j.icheatmasstransfer.2022.106102.
[2] Poós, T.; Varju, E.: Mass transfer coefficient for water evaporation by theoretical and empirical correlations. International Journal of Heat and Mass Transfer 153, 2020, 1-10, DOI: 10.1016/j.ijheatmasstransfer.2020.119500.
Required language skills: English Number of students who can be accepted: 1
Deadline for application: 2024-10-15
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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