The air swirl diffusers are popular for the ceiling level air supply system and have been widely used for Indoor Air Quality. They are nowadays one of the most popular diffusers commonly used in ...airconditioning systems 1, 2. The swirl diffusers are intended to use in low- and medium-pressure ventilation systems. They allow for obtaining the swirl airflow and are especially recommended to use in spaces with the height from 3m up to 12m, where heating and cooling is performed by the ventilation system and where the exact setting of supply air velocity is important 3-6. In the case of swirl diffusers,fluid flow is usually significantly influenced by the characteristics of different diffuser designs. In the ventilation system design phase, a typically focus on ventilation effectiveness and takes into account a large number of parameter. However, the discrepancy between design and practice are often experienced mainly because operating conditions don’t correspond to the designing conditions 7-9. Inthis work, the airflow of swirl diffuser has been studied using Particle Image Velocimetry (PIV) method to analyse the mean airflow and geometry influence on the results. The paper presents a comparison of the results of velocity field measurements using the PIV method and the results obtained by means ofnumerical analysis CFD. Based on the analysis the velocity flow field was evaluated and the range of effective operation of the diffuser have been determined 10.
One of the examples of how atmospheric air could be utilized includes its use as a carrier of mechanical energy transmitted by various devices, e.g. air compressors, constituting parts of various ...technical systems. In many of them, atmospheric air is subjected to significant changes in static pressure. This research paper specifies the effect of the variable static pressure on the dew point temperature of wet air. This issue was presented both analytically and graphically. The knowledge will allow to effectively identify these areas in which the water vapour contained in the air will be subject to phase changes, unfavourable for humans.
In the article, analysis of heat exchangers, working together with air-conditioning system, are presented. For an object with known requirement to hot and cold, air heat exchanger (ground type) is ...designed. For that defined system, the energy analysis of heat exchanger’s energy work in yearly cycle, including a work of air treatment with full (cooling - desiccation and heating of air in the summer, heating and moisturizing in the winter) and not quite full (cooling of air in the summer, heating of air in the winter) air-conditioning are examined. Effects connected with a reduction of energy costs needed for heat treatment of air blown to the room are specified included the climatic conditions like air heating and cooling degree-hours.
Artykuł dotyczy zagadnienia zastosowania innowacyjnego rozwiązania służącego do czyszczenia maszyn i urządzeń znajdującychsię w wyrobiskach górniczych z zastosowaniem technologii UCT (Underground ...Cleaning Technology). Podczas czyszczenia podawanajest pod ciśnieniem mieszanina gazów składająca się w głównej mierze z dwutlenku węgla (suchy lód), który sublimując zwiększaefektywność czyszczenia. Podczas prac powstaje zapylenie powietrza wynikające z obecności w wyrobisku nagromadzeń pyłuwęglowego i kamiennego oraz z emisji pyłów z procesu czyszczenia. W artykule przedstawiono wyniki pomiarów rozkładu zapyleniana stanowisku pracy oraz w jego otoczeniu. W procesie czyszczenia zastosowano aktywne sposoby redukcji zapylenia powietrzaza pomocą suchego odpylacza filtracyjnego. Badaniami objęto również strumień powietrza na wlocie do odpylacza oraz na jegowylocie. Na podstawie wykonanych pomiarów in situ oceniono wpływ metody czyszczenia urządzeń górniczych na stan powietrza wwyrobisku oraz możliwości zastosowania technologii UCT w podziemnych zakładach górniczych.
Artykuł dotyczy zagadnienia zastosowania innowacyjnego rozwiązania służącego do czyszczenia maszyn i urządzeń znajdującychsię w wyrobiskach górniczych z zastosowaniem technologii UCT (Underground ...Cleaning Technology). Podczas czyszczenia podawanajest pod ciśnieniem mieszanina gazów składająca się w głównej mierze z dwutlenku węgla (suchy lód), który sublimując zwiększaefektywność czyszczenia. Podczas prac powstaje zapylenie powietrza wynikające z obecności w wyrobisku nagromadzeń pyłuwęglowego i kamiennego oraz z emisji pyłów z procesu czyszczenia. W artykule przedstawiono wyniki pomiarów rozkładu zapyleniana stanowisku pracy oraz w jego otoczeniu. W procesie czyszczenia zastosowano aktywne sposoby redukcji zapylenia powietrzaza pomocą suchego odpylacza filtracyjnego. Badaniami objęto również strumień powietrza na wlocie do odpylacza oraz na jegowylocie. Na podstawie wykonanych pomiarów in situ oceniono wpływ metody czyszczenia urządzeń górniczych na stan powietrzaw wyrobisku oraz możliwości zastosowania technologii UCT w podziemnych zakładach górniczych.
In this article, a theoretical mathematical model of gas flow through a duct in the case of local mass and momentum sources and sinks is presented. The continuity equation and motion equation with ...one-dimensional, density-stable gas flows were used to create this model. The size of sources and sinks and their locations have an effect on the size of gas stream flows in the duct, gas energy losses, and the parameters of the mechanical source energy that is causing the flow. In the traditional approach to describing the gas flow in the duct, the concept of resistivity and the equivalent resistance of the conduit is used. In the case of flow in the duct with local mass and momentum sources and sinks, the transport resistance depends on a bigger number of parameters than the concept of specific resistance usage. The location and size of the source flux or mass and momentum sinks and the fan work (suction, blowing) were taken into account in the presented model. The model gives the opportunity to determine the mechanical energy losses and efficiency of gas transport in the duct.
In this article, the analysis of mechanical energy changes in a gas medium flow with stable and variable density was presented. To determine the energy losses, the various sources of momentum and ...mass were used, which had an influence on air flow through the conduit in the system without heat exchange with the environment. The occurrence of varying density gas flow in the conduit (caused by local inflow of mass and momentum) in inclined pipes generates a natural depression–internal mechanical energy. The local momentum sources can facilitate or hinder the gas flow through the conduit. This phenomenon often appears in the network of underground mine workings and in ventilation and air conditioning installations. The characteristic for gas flow through a pipe or mining excavation is the equivalent aerodynamic resistance, the value of which is influenced by the mass and momentum of local sources. This value determines the facilitation or difficulty in gas transport through a section of conduit in relation to the mass stream of the medium. In this article, the dependency of mass flow and gas momentum with different densities on the value of the gas medium flow resistance in the conduit was analyzed. On the basis of the obtained results, the loss of mechanical energy and energy efficiency of flows were determined. In this work, two cases of fan work in suction and blowing modes were analyzed. For these examples, a gas inflow with three different mass streams, a density higher than the main stream density, and with a zero momentum value for this stream was modeled. Ten cases of mass inflow sources were considered. The results of the gas mass flow calculation through the fan m˙w and gas m˙0 and the coefficient of transport efficiency are graphically presented in the paper.
Increasing emissions from mining areas and a high global warming potential of methane have caused gas management to become a vital challenge. At the same time, it provides the opportunity to obtain ...economic benefits. In addition, the use of combined heat and power (CHP) in the case of coalbed methane combustion enables much more efficient use of this fuel. The article analyses the possibility of electricity production using gas engines fueled with methane captured from the Budryk coal mine in Poland. The basic issue concerning the energy production from coalbed methane is the continuity of supply, which is to ensure the required amount and concentration of the gas mixture for combustion. Hence, the reliability of supply for electricity production is of key importance. The analysis included the basic characterization of both the daily and annual methane capture by the mine’s methane drainage system, as well as the development of predictive models to determine electricity production based on hourly capture and time parameters. To forecast electricity production, predictive models that are based on five parameters have been adopted. Models were prepared based on three time variables, i.e., month, day, hour, and two values from the gas drainage system-capture and concentration of the methane. For this purpose, artificial neural networks with different properties were tested. The developed models have a high value of correlation coefficient. but showed deviations concerning the very low values persisting for a short time. The study shows that electricity production forecasting is possible, but it requires data on many variables that directly affect the production capacity of the system.
In buildings, the HVAC systems are responsible for a major part of the energy consumption. Incorrect design or selection of the system and improper installation, operation, and maintenance of the ...systems’ elements may result in increased energy consumption. It is worth remembering that the main aim of the appropriate system is to maintain the high quality of the indoor environment. Appropriate selection of the HVAC solution ensures both thermal and quality parameters of the air, independently of the internal and external heat loads. The microclimate of a room is affected not only by air temperature, humidity, and purity, but also by air velocity in the occupied zone. The proper air velocity distribution prevents discomfort, particularly at workstations. Based on the measurements in the office building, an analysis of velocity profiles of air supplying two different types of linear diffusers was carried out. The analysis was made based on the results of measurements performed with thermoanemometers in the actual facility. During the study, temperature of the supply air was lower that the air in the room. Analysis was focused on the airflow fluctuation and its impact on the users’ comfort. This is an obvious topic but extremely rarely mentioned in publications related to air diffusers. The results show the importance of air fluctuation and its influence on the users’ comfort. During the measurements, the instantaneous air velocity for one of the analyzed types of the diffuser was up to 0.34 m/s, while the average value from the period of 240 s for the same measuring point was relatively low: it was 0.19 m/s. Only including the airflow variability over time allowed for choosing the type of diffuser, which ensures the comfort of users. The measurements carried out for two linear diffusers showed differences in the operation of these diffusers. The velocity in the occupied zone was much higher for one type (0.36 m/s, 3.00 m from diffusers) than for another one (0.22 m/s, 5.00 m from diffusers). The improper selection of the diffuser’s type and its location may increase the risk of the draft in the occupied zone.
Greenhouse gases such as carbon dioxide and methane cause global warming and consequently climate change. Great efforts are being made to reduce greenhouse gas emissions with the objective of ...addressing this problem, hence the popularity of technologies conductive to reducing greenhouse gas emissions. CO2 emissions can be reduced by improving the thermal efficiency of combustion engines, for example, by using cogeneration systems. Coal mine methane (CMM) emerges due to mining activities as methane released from the coal and surrounding rock strata. The amount of methane produced is primarily influenced by the productivity of the coal mine and the gassiness of the coal seam. The gassiness of the formation around the coal seam and geological conditions are also important. Methane can be extracted to the surface using methane drainage installations and along with ventilation air. The large amounts of methane captured by methane drainage installations can be used for energy production. This article presents a quarterly summary of the hourly values of methane capture, its concentration in the methane–air mixture, and electricity production in the cogeneration system for electricity and heat production. On this basis, neural network models have been proposed in order to predict electricity production based on known values of methane capture, its concentration, pressure, and parameters determining the time and day of the week. A prediction model has been established on the basis of a multilayer perceptron network (MLP).
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