•A new construction of rotary heat exchanger with bypass dampers.•Thermal behaviour of rotary heat exchanger with bypass dampers.•The effect of bypass opening on pressure loss of heat ...exchanger.•Energy savings potential of rotary heat exchanger with bypass dampers.•Economic benefit – return on investment.
The article deals with the possibilities of using a bypass damper in a rotary regenerative heat exchanger for heat recovery in ventilation and air conditioning system and calculates the energy savings related to overcoming the pressure loss of the exchanger. For the purposes of the analysis, a prototype heat exchanger with a wheel diameter of 1000 mm and bypass damper with a diameter of 200 mm was designed and constructed. The exchanger was subjected to an experimental investigation in order to determine its behaviour. The pressure loss of the exchanger, depending on the air flow rate, as well as the pressure loss for three nominal air flow rates, depending on the opening of the bypass damper, were measured. The measurement showed that the new exchanger design enables a reduction in the pressure loss of the exchanger by up to 49% compared to the original value. Based on the measured values, an analysis of the potential savings of electrical energy for driving fans in various European cities was carried out. The energy savings depend on the given climatic location where the exchanger will be used and on the operating time of the air handling unit. From the analyses carried out, it is clear that, by including the bypass damper, 18 to 44% of the electrical energy of the fan can be saved, which overcomes the pressure losses of the heat exchanger. Based on the current electricity prices, the return on the investment for the bypass damper was calculated based on the price of electricity at the given time and place (Prague - Czech Republic, 2022), which is from 0.5 to 3 years, depending on the type and period of operation of the air handling unit equipment, at common air velocities.
•Pressure loss of rotary regenerative heat exchangers.•Experimental investigation of eight different wheel geometries.•Evaluation of the coefficient of friction in wheel channel.•Influence of the ...leakage on pressure loss of the built-in rotary heat exchanger.•New correlation of the pressure loss data.
The pressure loss of the rotary exchanger is an important parameter that affects the energy consumption. Based on the literature review, the available correlations for calculating the pressure loss of rotary regenerative heat exchangers are presented in the article. The article presents extensive experimental research of rotary regenerative exchangers with different wheel geometries. A total of nine exchangers with eight different heat wheel geometries were investigated. The experiment was divided into two tasks concerning the pressure loss of the wheel channel and the total pressure loss of the built-in exchanger. The results of both approaches show differences that are caused by the leakage of rotary exchangers, which is their natural property. Based on the results of the experiment, correlations were proposed for determining the coefficient of friction in a channel in the shape of a sinusoid and a correlation for calculating the total pressure loss of the built-in rotary exchanger. The presented correlations have been experimentally verified and can be applied with a sufficient accuracy of ±5%. The new correlations were compared with the published results. The article discusses the effect of leakage of exchangers equipped with a labyrinth seal. Based on the experimental investigation, it was found that the leakage of the examined exchangers varies in a wide range of 1 to 4% and depends on the quality of the exchanger construction.
Due to the different approaches in determining the ventilation airflow rate per person for workspaces, where high-temperature air conditioning systems are used for air conditioning, problems with the ...condensation of water vapour on the cold surfaces of the system can occur. The article analyses the risk of condensation in various European cities using the available climatic data. Systems with cooling ceilings and cooling beams with a ventilation device operating in parallel are taken into account. Different ventilation airflow rates per person were analysed. On the example of a room equipped with high-temperature cooling, an energy simulation calculation is performed, which includes a ventilation and air-conditioning system with the possibility of capacity control. It is clear from the results that the condensation of water vapour can be prevented by technical measures at the cost of reducing the cooling capacity, which can affect the achievement of the thermal comfort of those present. In the end, suitable solutions are discussed, which should already be adopted at the time the device is designed so that the risk of condensation is not a major obstacle in the operation of these energy-efficient systems. An irreplaceable role in the operation of high-temperature cooling systems is played by a measurement and control system with a suitable algorithm to prevent condensation.
Mesenchymal stem cells (MSCs) are multilineage cells able to differentiate into other cell types. MSCs derived from bone marrow or compact bones are the most accessible stem cells used in tissue ...engineering. Therefore, the aim of this study was to isolate, characterize and cryopreserve MSCs of endangered Oravka chicken breed. MSCs were obtained from compact bones of the femur and tibiotarsus. MSCs were spindle-shaped and were able to differentiate into osteo-, adipo-, and chondrocytes under the specific differentiation conditions. Furthermore, MSCs were positive for surface markers such as CD29, CD44, CD73, CD90, CD105, CD146 and negative for CD34CD45 by flow cytometry. Moreover, MSCs demonstrated high positivity of “stemness” markers aldehyde dehydrogenase, alkaline phosphatase as well as for intracellular markers vimentin, desmin, α-SMA. Subsequently, MSCs were cryopreserved using 10% dimethyl sulfoxide in liquid nitrogen. Based on the results from the viability, phenotype, and ultrastructure assessment we can concluded that the MSCs were not negatively affected by the cryopreservation. Finally, MSCs of endangered Oravka chicken breed were successfully stored in animal gene bank, thus making them a valuable genetic resource.
The pressure loss of a duct affects the functionality of the ventilation equipment, the noise and especially the consumption of electricity to drive the fans. In addition, the pressure drop of the ...pipe is an important piece of information that serves to correctly design the ventilation system. The aim of the study is to determine the pressure drop of flexible hoses of relatively small diameters of 63–160 mm, used mainly for residential ventilation and to study the effect of compression. Four types of ducts, which differ in terms of the shape and material used, were subjected to experimental investigations. Based on the pressure loss measurement, the friction factor f and absolute roughness ε of the flexible ducts in the fully extended state were evaluated. The absolute roughness of the pipe ε varies over a wide range of values (from 0.04 to 2) depending on the material used. It was experimentally confirmed that the plastic ducts behave almost hydraulically smooth in the extended state. The effect of compression on the pressure drop was monitored in two ducts formed by a spirally wound wire. It was found that the pressure drop increases almost linearly with the increasing compression. It is clear from the results that the effect of compression is a major problem for small diameters (80–160 mm). For a compression factor of 15%, the pressure drop of the flexible ducts is 4–8 times higher than in the fully extension state. The key benefit is the knowledge of the pressure loss of flexible air ducts of small diameters depending on the compression ratio.
•Pressure loss of flexible duct of small diameters (80–160 mm) in extended state.•Experimental investigation of four different types of flexible ducts.•Evaluation of friction factor f on the Reynolds number.•New absolute roughness ε of the inner surface of the fully extended flexible ducts.•Influence of the duct compression of small diameters on the pressure loss.
The article deals with the hydraulic behaviour of capillary mats most often used for high-temperature cooling or low-temperature heating of buildings. On the basis of experimental measurements, the ...dependences of the pressure loss of the capillary mats on the water flow rate in relation to their geometrical arrangement were obtained. The measured values were compared with the manufacturer's data and it was found that the measured values differ significantly. The CFD simulation method was used to model the pressure losses of the capillary mats. The main emphasis was placed on the friction losses in the capillary during laminar fluid flow and local losses during the branching and coupling of the flows for the changing flow regime. Based on the simulation calculations, the dependences of the local loss coefficient during the flow diverging and converging and the relationship for the calculation of the coefficient of friction in the unsteady region of laminar flow were obtained. Based on the obtained results, an analytical computational model was built to determine the pressure losses of the capillary mats based on an iterative and approximate solution. The example shows the differences between the different approaches to the solution. The results of the presented model are compared with the experimentally obtained data. The article presents the share of partial components in the total pressure loss of the mats.
•Unique measuring track for measuring the pressure loss of capillary mats.•Local pressure losses in laminar flow regime during diverging and converging.•The CFD model of two capillaries with a small inner diameter.•Coefficient of friction in the transient flow region.•Analytical model of the pressure loss of capillary mats.
The paper presents a new method to determine the sensible effectiveness and pressure loss of rotary regenerative heat exchangers using computational fluid dynamics (CFD). It is based on CFD ...simulations of a single thermal wheel microchannel with a small cross-sectional area and thin walls, with cyclic inlet and outlet boundary conditions. Two unique measurement set-ups were designed and built for the experimental measurement of the heat exchanger characteristics. Five different types of thermal wheels were manufactured, measured, and simulated in ANSYS Fluent. All wheels achieve an effectiveness greater than 73% under certain (air flow) conditions, which is the minimum effectiveness required by Ecodesign (in the EU). For the examined exchangers, the effectiveness ranges from 66.5% to 83.3%, depending on the boundary conditions and geometric parameters of the rotors. The highest sensible effectiveness is achieved by heat exchangers with the largest heat exchange surface
A
c
; on the other hand, these wheels have the largest pressure loss. The paper discusses the use of a simplified
ε
-NTU correlation model for the HVAC systems (typically
C
* = 1). The correlation model and CFD results were compared and found to be different from each other. The results of the CFD simulation were compared with measurements to prove that the proposed simulation method can predict the behaviour of the real heat exchanger as a whole. It was demonstrated that the sensible effectiveness and pressure loss of the rotary heat exchanger predicted by the CFD simulations correspond well to the measured values within the measurement uncertainty ±1.3%. The proposed method can be used for the comparison of different rotary regenerative heat exchangers before their manufacturing and for verification that they meet the EU Ecodesign requirements set by the current legislation. It reduces the cost of the initial optimisation and testing of new designs.
The aim of this study was to evaluate the effect of phytogenic additive with anti‑inflammatory and antioxidant properties on thermoregulatory behavior (lifting of the wings, high respiratory rate ...defined as open beaks) and water and feed intake in mild‑moderate heat stressed Cobb 500 broiler chickens. From 28th day of chickens’ age experimental group was supplemented with 0.1 % phytogenic additive based on Scutellaria baicalensis L. extract in the diet. At the age 30 days temperature was increased to 27 °C and kept the same till the end of experiment at 34 days of age. Ethological observation was performed 31st, 32nd and 33th days of experiment. Monitoring was performed in three observation periods at the start, in the middle and at the end of 18h day length, always for three consecutive hours. Changes in chickens’ behavior among days and observation periods, as well as the influence of phytogenic additive were evaluated. Manifestations of thermoregulatory behavior were significantly higher (p < 0.001) in the middle and at the end of photoperiod. Significantly the highest number of chickens fed diets (p < 0.001) at the end of day‑light, water intake was the lowest in the middle of the day (p < 0.001). Significantly the oftenest lifting of the wings (p < 0.001), high respiratory rate (p < 0.001) and feed intake (p = 0.017) were found in 33 days of chickens’ age. Feeding of phytogenic additive did not affect water intake and feed intake, anyway significantly reduced (p < 0.001) thermoregulatory behavior.
The current regulation of European Commission No. 1253/2014 regarding Ecodesing requirements for ventilation units, which classified them based on the Specific Fan Power (SFP), has been driving the ...innovation in the sector of air-handling systems. The required energy saving can be met by applying modern and energy efficient Electronically Commutated (EC) motor which, at the same time, significantly change the internal geometry of the fan unit. The paper deals with design of a new type of modular fan unit ALTEKO Alton with EC motor and unhoused backward curved impeller. The design development and optimization of the fan unit leading to the reduction of generated aerodynamic noise, lower pressure loss and better outflow characteristics is supported by the Computational Fluid Dynamic (CFD) simulations, which enables visualization of air streamlines, velocities and pressure contours within the unit. Such a design is an iterative process between CFD specialist and construction team, where, based on the simulated results, the critical spots are identified, the geometry is improved and again verified throughout the CFD simulation. The paper describes in detail the individual steps of the optimization study, starting with the import of the detailed geometry from the design CAD software and its necessary simplification for the use in the CFD study, meshing of the model and consequent simulation. The methods of the fan rotation approximation are discussed as well. Additionally, the optimum position of heat exchanger in front of the fan unit is addressed. The presented work is a part of a project supported by the EU under the Operational Program Enterprise and Innovation for Competitiveness.
Heat stress (HS) in poultry husbandry is an important stressor and with increasing global temperatures its importance will increase. The negative effects of stress on the quality and quantity of ...poultry production are described in a range of research studies. However, a lack of attention is devoted to the impacts of HS on individual chicken immune cells and whole lymphoid tissue in birds. Oxidative stress and increased inflammation are accompanying processes of HS, but with deleterious effects on the whole organism. They play a key role in the inflammation and oxidative stress of the chicken immune system. There are a range of strategies that can help mitigate the adverse effects of HS in poultry. Phytochemicals are well studied and some of them report promising results to mitigate oxidative stress and inflammation, a major consequence of HS. Current studies revealed that mitigating these two main impacts of HS will be a key factor in solving the problem of increasing temperatures in poultry production. Improved function of the chicken immune system is another benefit of using phytochemicals in poultry due to the importance of poultry health management in today’s post pandemic world. Based on the current literature, baicalin and baicalein have proven to have strong anti-inflammatory and antioxidative effects in mammalian and avian models. Taken together, this review is dedicated to collecting the literature about the known effects of HS on chicken immune cells and lymphoid tissue. The second part of the review is dedicated to the potential use of baicalin and baicalein in poultry to mitigate the negative impacts of HS on poultry production.
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