ABSTRACT
Thermal energy accumulation is one of the ways how to optimize heat production processes and how to balance the supply and demand of heat in distribution systems. This article presents a design of a fin-and-tube latent heat thermal energy storage (LHTES), which combines high thermal energy storage density and scalability. A computational model that used lumped heat capacities was tuned using the experimental data. The numerical model proved to be simple yet precise. A new constant mixing temperature test was designed and performed with the LHTES. Unlike standard constant flow rate charge/discharge test, this test provided valuable information about what to expect in the real-life operation conditions. From the tests and data from simulations, it was concluded that the LHTES would perform better in terms of its capacity utilization if it operated at lower output power than in the laboratory circuit. This indicates that a smaller, and thus more cost-effective, LHTES could be employed in the laboratory circuit with virtually the same utility to the system if its heat transfer characteristics were improved.
ABSTRACT
Heat storage efficiency is required to maximize the potential of combined heat and power generation or renewable energy sources for heating. Using a phase change material (PCM) could be an attractive choice in several instances. Commercially available paraffin-based PCM was investigated using T-history method with sufficient agreement with the data from the manufacturer. The introduced LHTES with cylindrical capsules is simple and scalable in capacity, charging/discharging time, and temperature level. The overall stored energy density is 9% higher than the previously proposed design of similar design complexity. The discharging process of the designed latent heat thermal energy storage (LHTES) was evaluated for two different flow rates. The PCM inside the capsules and heat transfer fluid (HTF) temperature, as well as the HTF flow rate, were measured. The lumped parameter numerical model was developed and validated successfully. The advantage of the proposed model is its computational simplicity, and thus the possibility to use it in simulations of a whole heat distribution network. The so-called state of charge (SoC), which plays a crucial role in successful heat storage management, is a part of the evaluation of both experimental and computational data.
ABSTRACT
A passive biomonitoring survey using terrestrial mosses was performed in a heavily polluted industrial region on the border between Czechia and Poland in a regular grid of 41 sampling points. The concentrations of 38 elements were determined in the moss samples, using Neutron Activation Analysis (NAA). Simultaneously, air pollution modelling was performed using the Czech reference methodology Symos'97 for the year of the sampling (2015) and 3 years prior (2012) in order to compare the results of both the approaches and evaluate the credibility of the moss biomonitoring method. The NAA results were transformed according to the principles of compositional data analysis and assessed using hierarchical clustering on principal components. The resulting clusters were compared with the results of air pollution modelling using one-way analysis of variance. The association of determined clusters with the pollution from industrial sources was confirmed only for the results of the 2012 modelling. This validates the complementarity of the air pollution modelling and the moss biomonitoring, ascertains the moss biomonitoring as a valid method for long-term pollution assessment and confirms one of the fundamentals of moss biomonitoring, the reflection of the atmospheric conditions prevailing in the period before the sampling.
