Numerical Investigation of a Friction Ventilator for Different Geometrical Setups

2016 ◽  
Vol 19 ◽  
pp. 35-42 ◽  
Author(s):  
Julian Praß ◽  
Andreas Renz ◽  
Johannes Weber ◽  
Stefan Becker ◽  
Jörg Franke
Keyword(s):  
Heat Exchangers ◽  
Heat Recovery ◽  
Ventilation System ◽  
Pressure Jump ◽  
Noise Generation ◽  
Temperature Level ◽  
Pressure Losses ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Novel Concept

Conventional ventilation systems with heat recovery used for building aeration exhibit characteristic disadvantages arising from their operating principle such as noise generation from bladed ventilators or remarkable pressure losses generated by heat exchangers. A novel concept that combines ventilators and heat exchanger in one compact friction ventilator that rotates in two separated ducts producing two opposed airflows and transferring thermal energy from the higher temperature airflow to the lower temperature level can overcome the mentioned shortcomings. In order to demonstrate the feasibility of a friction ventilator to operate as ventilation system with heat recovery computational fluid dynamics were used to analyze the resulting pressure jump and volume flow for different geometrical setups. An extensive grid dependency study for a defined operating point that represents the typical use has been carried out in order to improve the numerical results. Furthermore, the results were compared to experimental data whenever possible.

Determining the impact of air-side cleaning for heat exchangers in ventilation systems

2019 ◽  
Vol 41 (1) ◽  
pp. 46-59 ◽  
Author(s):  
Akram Abdul Hamid ◽  
Dennis Johansson ◽  
Michael Lempart
Keyword(s):  
Pressure Drop ◽  
Energy Loss ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Energy Use ◽  
Ventilation System ◽  
Field Measurements ◽  
The Impact ◽  
Over Time ◽  
Ventilation Systems

Cleaning coils can be an efficient way to reduce the need for reparations and maintain the functionality of a ventilation system. This study builds upon existing knowledge concerning the contamination of heat exchangers. Through field measurements on coils and heat-recovery units, a laboratory experiment on a coil, and a generic calculation example, this study determines the impact of sustained contamination on heat-recovery units with regards to energy use. Field measurements made before and after cleaning of heat exchangers show an average increase in the pressure drop by 12% and decrease in the thermal exchange efficiency by 8.1% due to mass deposited on the surface of the heat exchangers. Results from a laboratory test show a correlation between the mass deposited on a coil and (1) the increase in pressure drop over the coil, as well as (2) a diminishing heat exchange. Accumulating contamination on heat-recovery units in residential and commercial buildings (over time) is then linked to increasing pressure drop and diminishing thermal efficiency. With models based on these links, energy loss over time is calculated based on a generic calculation example in a realistic scenario. Practical application: The results from this study emphasize the need for maintenance of buildings with ventilation systems with coils, but more so those with heat-recovery units. The presented field measurements and laboratory study correlate energy loss with sustained accumulation of contaminants on coils and heat-recovery units. These results should serve as a recommendation to property owners considering maintenance of such units in their buildings.

scholarly journals Verification and validation of a CFD model of a fixed regenerator for heat recovery from air

2021 ◽  
Vol 327 ◽  
pp. 01008
Author(s):  
Angel Penev ◽  
Lyubomir Tsokov ◽  
Momchil Vassilev
Keyword(s):  
Numerical Model ◽  
Heat Recovery ◽  
Model Simulation ◽  
Ventilation System ◽  
Verification And Validation ◽  
Analytical Models ◽  
Pressure Losses ◽  
Mass Transfer Processes ◽  
Local Ventilation ◽  
Cfd Method

The article presents verification and validation of a numerical model of conjugated heat and mass transfer processes and aerodynamics in a fixed "honeycomb" type regenerator with square channels for heat recovery from the exhaust air of a local ventilation system. The processes in the regenerator are simulated by the CFD method. The influence of the processes of condensation and evaporation of moisture in the humid air on the efficiency of the regenerator has been investigated through these simulations and is shown in the article. The calculations of the fixed regenerator's thermal efficiency and pressure losses are made by known analytical models and the results are compared with those of the numerical model. The article compares the model simulation results with experimental data and data from reference sources.

scholarly journals Analysis of the influence of condensation temperature and compressor efficiency on heat pump system efficiency

2021 ◽  
Vol 1208 (1) ◽  
pp. 012015
Author(s):  
Nemanja Koruga ◽  
Mirko Dobrnjac ◽  
Dušan Golubović ◽  
Nemanja Dobrnjac
Keyword(s):  
Heat Pump ◽  
Working Fluid ◽  
Condensation Temperature ◽  
Temperature Level ◽  
Pump System ◽  
Heat Pump System ◽  
Higher Temperature ◽  
Mutual Conversion ◽  
Lower Temperature ◽  
Compressor Efficiency

Abstract In heat pump cycles, heat is supplied to the working fluid from a certain group of low-temperature bodies and transferred to a group of high-temperature bodies, i.e. the heat source is at a lower temperature and the heat sink at a higher temperature. Using the method of circular processes, in synergy with the possibility of mutual conversion of thermal and mechanical interactions, the process of heat transfer from a lower temperature level to a higher temperature level is enabled. Mechanical work, which, as compensation, should be given by the environment to the system (working substance), is a difference between heat removed and heat supplied. The efficiency of the heat pump mostly depends on the temperature interval at which the process takes place, however, the efficiency of the heat pump is also affected by the thermodynamic parameters of its parts: compressor, condenser, throttle valve, and evaporator. In this paper, the influence of condensing temperature and compressor efficiency on the efficiency of the system as a whole is examined. The calculation was performed for two working substances, R123 and R134a, using the EES software package (Engineering Equation Solver) which is used for numerical modeling of thermodynamic systems, process optimization, and making process diagrams.

Influence of Magnetic Field on the Mechanical Properties of Austempered Ductile Iron (ADI)

2007 ◽  
Vol 539-543 ◽  
pp. 4657-4662
Author(s):  
Susil K. Putatunda
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
High Magnetic Field ◽  
Ductile Iron ◽  
Austempered Ductile Iron ◽  
Quenching Media ◽  
Fine Grain ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Novel Concept

A novel concept of two-step austempering in a magnetic field has been conceived by this investigator. This twostep process involves first quenching the alloy to a lower temperature after austenitizing and then immediately rising the temperature of the quenching media to a higher temperature and the whole austempering process is carried out in the presence of a high magnetic field. In this investigation, Austempered Ductile Iron (ADI) was processed by this novel two-step austempering process in a high magnetic field of 20 Tesla. The microstructure and the mechanical properties of the ADI processed in a magnetic field has been characterized and compared with ADI processed by conventional process. The results of this investigation indicate significant improvement in the mechanical properties of ADI when Austempered in a high magnetic field. Both yield and tensile strengths were higher in the samples processed in the presence of a magnetic field. Very fine grain ferrite and austenite was obtained in the microstructure. The ferrite content was also significantly higher.

scholarly journals Efficiency Improvement of Miniaturized Heat Exchangers

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 25
Author(s):  
Iris Gerken ◽  
Thomas Wetzel ◽  
Jürgen J. Brandner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Assessment Method ◽  
Flow Path ◽  
Transfer Enhancement ◽  
Pressure Losses ◽  
Pin Fin ◽  
Additional Pressure ◽  
The Impact

Micro heat exchangers have been revealed to be efficient devices for improved heat transfer due to short heat transfer distances and increased surface-to-volume ratios. Further augmentation of the heat transfer behaviour within microstructured devices can be achieved with heat transfer enhancement techniques, and more precisely for this study, with passive enhancement techniques. Pin fin geometries influence the flow path and, therefore, were chosen as the option for further improvement of the heat transfer performance. The augmentation of heat transfer with micro heat exchangers was performed with the consideration of an improved heat transfer behaviour, and with additional pressure losses due to the change of flow path (pin fin geometries). To capture the impact of the heat transfer, as well as the impact of additional pressure losses, an assessment method should be considered. The overall exergy loss method can be applied to micro heat exchangers, and serves as a simple assessment for characterization. Experimental investigations with micro heat exchanger structures were performed to evaluate the assessment method and its importance. The heat transfer enhancement was experimentally investigated with microstructured pin fin geometries to understand the impact on pressure loss behaviour with air.

scholarly journals Sprouting of Sorghum (Sorghum bicolor [L.] Moench): Effect of Drying Treatment on Protein and Starch Features

Foods ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 407 ◽  
Author(s):  
Mia Marchini ◽  
Alessandra Marti ◽  
Claudia Folli ◽  
Barbara Prandi ◽  
Tommaso Ganino ◽  
...  
Keyword(s):  
Food Production ◽  
Cost Effective ◽  
High Exposure ◽  
Effective Technology ◽  
Drying Treatment ◽  
Higher Temperature ◽  
Lower Temperature ◽  
The One ◽  
Drying Conditions ◽  
Sorghum Bicolor L

The nutritional and physicochemical properties of sorghum proteins and starch make the use of this cereal for food production challenging. Sprouting is a cost-effective technology to improve the nutritional and functional profile of grains. Two drying treatments were used after sorghum sprouting to investigate whether the drying phase could improve the protein and starch functionalities. Results showed that the drying treatment at lower temperature/longer time (40 °C for 12 h) extended the enzymatic activity that started during sprouting compared to the one performed at higher temperature/shorter time (50 °C for 6 h). An increased protein hydrolysis and water- and oil-holding capacity were found in the flour obtained by the former treatment. Higher protein matrix hydrolysis caused high exposure of starch to enzymes, thus increasing its digestibility, while worsening the technological functionality. Overall, modulating drying conditions could represent a further way, in addition to sprouting, to improve sorghum flour’s nutritional profile.

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