Methods for the calculation of the undisturbed ground temperature (UGT) are presented. Heat fluxes occurring on the surface of the ground and their influence on the UGT are described. Correlation equations for the calculation of the undisturbed ground temperature based on the meteorological data averaged in the yearly cycle are proposed. These equations are of a semi-empirical character and they are based on the heat flux balance. The determined coefficients of these equations, particularly the convection heat transfer coefficient, are consistent with the values specified by other methods.
ABSTRACT:The dynamics of water vapour adsorption on silica gel coated on the metal pipe surface is studied. Those systems in which silica grains were used to coat the heat-exchanger pipes were utilized for heat-transfer enhancement in adsorption chillers. A mathematical model of this process, which takes into account the adsorption kinetics, is proposed. Experimental results for different gas velocities are presented in the form of breakthrough curves. They are used to verify the model and to determine the values of parameters characterizing the adsorption kinetics. The model is applied to predict the spatial and temporal variations of water concentration in the adsorbent layer (grains) covering the pipe and to determine the contribution of the internal mass transfer resistance (in grains) to the total mass transfer resistance (in both phases). It is revealed that the external resistance (in gas) is dominant over the internal resistance and that the contribution of the internal resistance increases with both time and gas velocity.
In this work, numerical simulation calculations were performed to investigate the minimum ground temperature that occurs when extracting thermal energy in a horizontal ground heat exchanger system in the Central European climate. The influence of ground thermal conductivity, heat flux extracted from the ground, periodic interruptions in the operation of the heat exchanger, periodic supply of heat energy to the ground, relative humidity of the ambient air, evaporation rate coefficient, and convective heat transfer coefficient on the ground minimum temperature were investigated. Based on the simulation, it was found that the high value of ground thermal conductivity favorably affects the operation of the installation with a ground heat exchanger. Both the reduction of the maximum heat flux taken from the ground, as well as periodic interruptions in the operation of the exchanger effectively protects the ground against excessive cooling. Further, it was found that heat supply to the ground in summer only slightly raises its minimum temperature, as well as the decrease of the relative humidity of the ambient air and evaporation rate coefficient. The change of the convective heat transfer coefficient has no significant impact on the minimum annual ground temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.