Heat transfer analysis on the growth of artificial sea ice using dynamic temperature profiles in an idealised environment

Guni, Felix

Heat transfer analysis on the growth of artificial sea ice using dynamic temperature profiles in an idealised environment

Thesis / Dissertation

2023

Abstract

Heat exchange between the atmosphere and the ocean plays a significant role over the Earth's climate, such that despite its complexity, it is essential to fully characterise it. Notably, sea ice growth occurs both in the Northern and Southern Hemisphere. It covers approximately 7% of the global surface area and reflects 40% of the radiation back into the atmosphere. However, over the past few decades there has been an increase in the global temperatures. This has led to the decrease in sea ice extents, and this continues to be accelerated by the positive-ice albedo effect. This effect of sea ice extents on the global climate requires research into models that can accurately predict sea ice growth. Sea ice growth is directly related to the heat exchanged at the ice-atmosphere interface. which can be approximated as the conductive heat flux at the top of the ice. The objectives of the project were to characterise the vertical conductive heat flux by developing models that can be used to solve the ice growth problem. The techniques developed would then be used to investigate the effect of varying the air temperature, starting solution salinity and tank size on the growth dynamics and conductive heat flux in artificial sea ice. Lastly, the project was aimed at predicting the temperature field in artificial sea ice through estimation of the thermal conductivity. The project therefore focuses on the development of a 1-D analysis model for the prediction of the vertical conductive heat flux, ice surface temperature and the average thermal conductivity using the temperature distribution of the ice. This was performed by assuming pseudo steady state and treating the ice growth problem as a moving boundary problem. The method for the prediction of the temperature field was based on solving the 1-D dynamic heat diffusion equation showing that the linear pseudo steady state assumption can be used to approximate the dynamic growth of ice and to estimate the model parameters. The results presented showed the assumption of pseudo steady state is valid for artificial sea ice that has a linear temperature profile with depth. As such the average thermal conductivity, ice surface temperature and heat linearly conducted through the ice were computed through regression of experimental temperature output data by linearisation of the heat diffusion equation. Regression of the temperature profile was performed at each measured time point. Lastly, it was shown that using the model parameters obtained from the linear analysis, a 1-D constant parameter dynamic model with a variable boundary was able to predict the dynamic growth of ice, within a least squares error of 0.31oC between the experimental and model data

Keywords

Engineering

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