Mugur C. Balan

Thermal Energy Efficiency Analysis for Residential Buildings

The paper presents an interactive software application, for the calculus of the heat flux demand in residential houses, based on international trends, standards and specifications in the fields of thermal energy in buildings. These types of calculations are considerable useful in the context of the large and constant interest on the subjects of energy conservation, reduction of polluting emissions and use on large scale of renewable energies. In order to reach the objective of the research, the heat flux demand was parameterized to identify each influence on the thermal energy consumption and costs. The development of the mathematical model had the aim to allow the minimization of the heat losses into the environment and to choose the correct thermal power for the residential houses heating devices. By the use of PHP language, the mathematical model has been transposed into a client-server application. The interactive software system has been validated through a case study and the obtained results were consistent and relevant. Based on the results it was possible to extract key conclusions about the parameters that contribute to the heat losses.

Software application for monitoring a small air conditioning unit

The paper presents the monitoring system of a small reversible air conditioning and heat pump device via the Internet. Presented are the construction of the equipment, the structure of the data acquisition and monitoring system, the structure of the database for storing the values of the monitored parameters and the software components used for data acquisition and storing. Also discussed are the parameters used for displaying the monitored information through a Web based software application. The overall design of the data acquisition system as well as the software application components are original

Timeline of Gas Production under Anaerobic Conditions

For the study of biogas production by anaerobic digestion of lignocellulose substrate, it was designed an experiment in which the quantity of gas released by the anaerobic hydrogen producing bacteria was measured. The experiment aimed to highlight the differences occurred in the quantity and composition of the gas provided in 5 consecutive experiments conducted in similar conditions. The experimental data were processed and it was analysed the timeline evolution of the gas production rate of which kinetic was numerically modelled by several three-parameter logistic functions. Even being a preliminary study, it is innovative because it combines experiment with simulation and it proved two mathematical models, based on Gompertz and logistic functions. It was found that the anaerobic digestion process with hydrogen production has a sigmoid dependence on time.

Simulation of heat transfer and pressure drop in bundles type air to air heat recovery equipment

This paper presents a comparative analysis between the results obtained with different equations for heat transfer coefficients and of pressure drop in heat recovery equipment with pipe bundles. The research method was based on different analytical equations available in literature, both for heat transfer coefficients and for pressure drop calculations. These equations were implemented in the Equation Engineering Software (EES) platform as part of this study. A total of 19 different equations for heat transfer coefficients inside and outside the pipes bundles and for the pressure drop calculations inside and outside the pipes bundles were studied. The air flow speed was considered up to 20 m/s, both inside and outside. This work presents a comparative study of the obtained results and a validation based on similar results available in literature. As conclusions, it was possible to select the most appropriate equations, to be used in the design of air to air heat recovery pipe bundle equipment.

Study of Ground – Water Heat Pump Parameters during 3 Years of Operation

The manuscript presents results of a 3 years experiment, concerning in the monitoring of working parameters of a ground – water heat pump with horizontal collectors. The measured working parameters of the refrigerant circuit are: evaporating pressure, condensing pressure, superheating temperature, discharge temperature, sub cooling temperature. There were also measured the flow rate and the temperatures on the heating circuit of water and on the horizontal collectors circuit with antifreeze. The methodology of data processing, described in the manuscript, allowed calculation of evaporating temperature and condensing temperature, based on measured corresponding pressures. The main obtained results consist in a complete set of working and performance parameters and their variation in 3 years of operation. Details are presented for operating conditions characteristic for different cases: middle of heating season, end of heating season, middle of non-heating season, beginning of heating season. Some practical conclusions of the study are also presented in the manuscript. It was indicated how the outside temperature is influencing the values of working and performance parameters, but mainly on the effective number of running periods.

Ground Temperature Variation around the Horizontal Collectors of a Heat Pump

The manuscript presents results of a 3 years experiment concerning the monitoring of temperature variation around a horizontal collector, coupled to a ground – water heat pump. Ground temperature was monitored in 7 (seven) measurement points: 1 (one) in the center of the collector area and 6 (six) at 15 cm, 30 cm and 60 cm of the collector boundary. The data processing methodology, described in the manuscript, allowed corrections, comparison with natural ground temperature variation and calculation of important characteristics of temperature variation in each measurement point. The main obtained results are: minimum, maximum and average temperatures, dates when minimum, maximum and average temperatures were reached, amplitude of temperatures variations and deviations comparing to natural ground temperature variation. The study of temperature field allowed the complete characterization of the ground temperature variation, including spatial and temporal variation. Some practical conclusions of the study are also presented in the manuscript. It was highlighted that due to a correct calculation of the collectors field size and to the presence of snow in each heating season of the 3 (three) years of the experiment, the ground temperature did not decreased below 2°C and the ground temperature recovered uniformly after each non heating season.

Modeling and experimental validation of the thermal behavior of PCM using DSC input data

The study presents a procedure for precise evaluation of the apparent heat capacity of phase change materials (PCM), based on differential scanning calorimetry (DSC). A mathematical model capable to predict the thermal behavior of a PCM within a latent heat thermal storage system was developed. The model takes into account the PCM’s apparent heat capacity variation with temperature. The model was validated with an experimental latent heat storage system presented in this study. It was found that the model is most accurate for PCMs with little or no subcooling and that validation of such models, on the designed laboratory equipment, should be carried out with reduced air flow rate. The average value of the mean bias error for the PCM and air temperature predictions were found to be 6.12% and 5.21% respectively.The study presents a procedure for precise evaluation of the apparent heat capacity of phase change materials (PCM), based on differential scanning calorimetry (DSC). A mathematical model capable to predict the thermal behavior of a PCM within a latent heat thermal storage system was developed. The model takes into account the PCM’s apparent heat capacity variation with temperature. The model was validated with an experimental latent heat storage system presented in this study. It was found that the model is most accurate for PCMs with little or no subcooling and that validation of such models, on the designed laboratory equipment, should be carried out with reduced air flow rate. The average value of the mean bias error for the PCM and air temperature predictions were found to be 6.12% and 5.21% respectively.

Orientation of Facades for Active Solar Energy Applications in Different Climatic Conditions

AbstractThis study presents an investigation concerning the conversion of solar radiation into heat, cold, and electricity on the facades of virtual buildings located in four different cities that ...

Hydrogen Production by Anaerobic Digestion of Biomass with High Lignocellulose Content - References Selection Procedure

The manuscript presents an objective and rigorous references selection procedure for a literature review concerning the state of the art in the field of bio-hydrogen production by anaerobic digestion of biomass with high lignocellulose content. The references selection procedure is presented in detail, with stages and different including and excluding criteria. The scientific databases and the key words used for their interrogation are also presented. The methodology of references selection consists of the following steps: automatic scientific databases interrogation, manual selection of references from the automatic interrogations results based on titles and abstracts, addition of new references based on study of references list from the previously selected papers, addition of references representing Romanian contributions and selection of papers based on preliminary study of their content. The main obtained results based on preliminary analysis of the selected references consist in presentation of the first published references, of the newest references and of the most cited references. It was highlighted that the trend of publication in anaerobic digestion of biomass with high lignocellulose content with the scope of hydrogen production, is in continuous increasing interest worldwide.