Application of the 2-D Trefftz Method for the Identification of Wave Flow Heat Transfer Coefficient in a Rectangular Minichannel. Energies. A Feasibility Study of Vehicle Air Conditioning System Application Using Vortex Tube.Energies.
Thermo-Economic Assessment of a Gas
Microturbine-Absorption Chiller Trigeneration System under Different Compressor Inlet
Air Temperatures
- Introduction
- Methodology
- Results and Discussion
- Conclusions
The turbine outlet gases (state 6) are directed to the preheater device where its temperature is reduced, and then to the heat recovery steam generator (HRSG) the heat transfer process allows us to generate steam (state 10), from water at ambient temperature (state 9). In the thermodynamic modeling of the trigeneration system [33], the components of the system are considered as open systems where a steady-state mass balance is applied according to equation (1).
Advance Exergo-Economic Analysis of a Waste Heat Recovery System Using ORC for a Bottoming Natural
On the other hand, the exogenous part of the exergy destruction is produced by the other components. Contribution of each component to the total exergy destruction of the cycle based on (A) traditional and (B) advanced exergy analysis.
A Li-Ion Battery Thermal Management System Combining a Heat Pipe and Thermoelectric Cooler
- Theoretical Analysis
- Numerical Simulations
- Experiment
- Discussion and Conclusions 1. Discussion
As shown in Figure 8, the surface temperature of the battery continued to rise during the discharge period. As the discharge rate increased, the discharge time shortened and the surface temperature of the battery increased.
Heat Transport Capacity of an Axial-Rotating Single-Loop Oscillating Heat Pipe for
Abrasive-Milling Tools
Experimental Preparation and Data Processing 1. Description of Experimental Apparatus
The SLOHP is mounted on the holder 30 mm away from its axis of rotation, which is the same as the radius of the OHP tool. Temperatures of the evaporator and condenser are measured by Omega type-K thermocouples (error limits: 0.4%). In this case, to study the thermal performance of the axial-rotating SLOHP under the same conditions with the abrasive-milling process, the rotation speed in the experiment is and 1500 rpm, with a relative centrifugal acceleration of and 738 m/s2.
Thermal resistance is used as a measure of the thermal performance of the axially rotating SLOHP.
Flow Visualization and Modeling
At the moment the evaporator is heated, the liquid turns into vapor, which causes the expansion of the vapor volume. The left term is the momentum produced by the vapor due to the vapor volume expansion. The first term of the right-hand side is the pressure differences acting on the liquid plug and vapor plug, while the second term of the right-hand side is due to the surface tension and the last term due to the shear stress between the wall and liquid.
The pressure of vapor and liquid is p1=p0,v+π. where p0,vandp0,la is the pressure of the vapor and liquid phases in a static state, Ris is the distance between the OHP and the axis of rotation and ω is the angular velocity.
Results and Discussion
However, when the centrifugal acceleration is large (e.g., 738 m/s2), the thermal efficiency of the methanol-filled axially rotating SLOHP is better than that of DI water. The effects of centrifugal acceleration, heat flux, and working fluid on the thermal performance of an axially rotating SLOHP are investigated through visualization, theoretical analysis, and experiments. Nevertheless, the heat capacity of the axially rotating SLOHP filled with DI water first increases and then decreases as the centrifugal acceleration increases.
Experimental investigation of thermal performance of the oscillating heat pipe for the grinding wheel.Int.
Problem Statement
In fact, the proposed model, based on a Lagrangian approach [10], was validated considering the working fluid as water and a reduced heat transfer between the pipes and the surroundings due to the great insulation of the pipes. In this contribution, the considered working fluid is oil and the heat transfer is higher due to the thermal energy recovered from the Sun. Therefore, the model is extended to include solar heating systems, taking into account the thermal solar gain and the inertia of the pipe system.
Although this paper focuses on the experimental validation of a medium-sized solar thermal plant, it can be extended to the modeling of larger solar plants, while the behavior of the main element, namely a tube, is studied and validated.
Modelling
In blue, the glass envelope; in grey, the metal tube; and in white, the vacuum between the two. It is assumed that temperatures, heat transfer coefficients and thermodynamic properties are considered uniform around the perimeter of the heat collector. Furthermore, thermal losses through the support fittings are neglected, and solar absorption in the tube and glass jacket is treated as a linear phenomenon [21].
Experimental Apparatus
The mass flow rate is derived from a data calibration study performed on the pump to evaluate it as a function of operating conditions. In Table 1, the working conditions of the main variables and the parameters of the external environment during the experimental campaign are reported. Mass Oil Flow Variation Experiment (MFE): a step change is imposed on the ETC inlet oil mass flow rate by varying the pump speed up or down, starting from a steady state.
Attempt to change the inlet oil temperature (TE): The oil temperature at the inlet to the ETC is varied by turning off the air cooler, starting from a steady state.
![Figure 2. Process flow diagram of the Parabolic Trough Test Loop (PTTL) facilities with the relative sensors and devices position [21].](https://thumb-ap.123doks.com/thumbv2/1libvncom/9201519.0/82.723.129.596.220.537/figure-process-diagram-parabolic-trough-facilities-relative-position.webp)
Results and Discussion
Again, the evolution of the predicted outlet temperature follows the experimental trends for several mass flow steps, inlet temperature steps, and solar energy steps or a combination thereof (Figure 4). Again, there is good agreement between plug flow modeling and experimental data for wide variations in mass flow rate, inlet pipe temperature, and solar irradiance. As shown in a previous modeling study of a district heating network, the thermal inertia of the system and the operating mass flow have a significant impact on the outlet temperature response.
Indeed, the mass flow rate influences how the fluid propagates in the pipe, while the influence of thermal inertia can be observed when the SBE conditions are set and can lead to a significant additional delay (more than 200 s) to get an outlet temperature with a value similar to the inlet temperature (considering the heat transfer to the ambient constant).
Conclusions
Indeed, in large networks with several intersections between pipes, the hydraulic part of the problem can become complex to solve due to the quadratic law relationship between pressure losses and mass flow rate. All results show a good agreement between experimental data and simulation results for a wide range of power plant operating conditions. In Proceedings of the 2nd International Conference on Computer Modeling and Simulation, Brno, Czech Republic, 5–7 September 2011; page
In Proceedings of the 14th International Society of Building Performance Simulation BS2015, Rome, Italy, 2–4 September 2019; pp.
Design Evaluation for a Finned-Tube CO 2 Gas Cooler in Residential Applications
Materials and Methods
The simulation model calculated the overall heat transfer coefficient of the gas cooler based on the mass flows, inlet and outlet temperatures, and pressures of the medium. The model used the average temperature and pressure of the mediums to calculate the heat transfer coefficients. The calculations were used to evaluate the overall performance of the gas cooler in different conditions.
Based on the off-design data, the overall heat transfer coefficient was calculated using Equations (3)-(17).
Results and Discussion 1. Validation of the Model
The increase in the water inlet temperature had a similar effect on the overall heat transfer coefficient of the heat exchanger Figure 5b. The absolute deviations between the model and the experiments were extracted and demonstrate the reliability of the selected heat transfer correlations. Increasing the fan frequency, water mass flow rate, and water inlet temperature resulted in an improvement in the overall heat transfer coefficient of the heat exchanger.
This procedure enables a reliable validation of the applied air-side heat transfer correlation.
Feasibility Study of a Centralised Electrically Driven Air Source Heat Pump Water Heater to Face Energy
Results
Figure 6 shows iso-lines of heating capacity as a function of rotation speed and ambient wet bulb temperature. A comparison with an actual machine was performed to validate the results of the heat pump model. A literature search was conducted to find an existing device that fits the characteristics of the modeled one.
On the other hand, the ratio between the thermal demand and the minimum heat capacity is on.
Discussion
In Figure 13, the average EPI obtained for residential blocks in Spain was represented through such a fitting curve, obtaining their heated area to maintain the same levelized costs as in the base case. Speed regulation in the compressor gives the heat pump the ability to meet almost all heating needs (96% in the base case) with good efficiency. In addition, total energy from renewable sources is obtained to meet the heating demand, taking into account both the energy supplied by the air and the share of renewable sources in the electricity mix (used for heat pump electricity consumption).
Accordingly, in the same example, the levelized heating costs decrease by €500 for a house of 100 m2 (with a base cost of €848).
Conclusions
Disponible en línea: https://www.miteco.gob.es/es/ministerio/planes-estrategias/estrategia-pobreza-energetica/actuali zaciondeindicadorespobrezaenergetica2019_tcm30-502983.pdf (consultado el 15 de abril de 2020). Disponible en línea: https://www.codigotecnico.org/images/stories/pdf/ahorroEnergia/CTE datosMET_20140418.zip (consultado el 9 de abril de 2020). Disponible en línea: https://www.certificadosenergeticos.com/wp-content/uploads/2018/12/informe-seguimiento-certi ficacion-energetica.pdf (consultado el 26 de mayo de 2020).
Dostopno na spletu: https://www.miteco.gob.es/es/ministerio/servicios/info rmacion/informacion-y-atencion-al-ciudadano/default.aspx (dostopano 14. maja 2020).
Applicability of Swaging as an Alternative for the Fabrication of Accident-Tolerant Fuel Cladding
Experimental 1. Swaging Method
The PST was synthesized by applying a pressure of 4 t/cm2 in the direction of the central axis of the double tube. Figure 1 shows a schematic of the swing method for the double tube and the type of stress applied to the tube during the process. Figure 2 shows that the inner surface of the outer tube and the outer surface of the inner tube adhere closely to each other.
It is imperative to note that gaps in the interface can degrade the mechanical and chemical properties of the pipe.
LUFDOR\
To confirm the diffusion behavior of the PST, an EDS analysis was performed, as shown in Figure 10. TEM analysis was performed to confirm the interfacial stability of the PST after exposure to high temperatures. Figure 11 is a cross-sectional TEM image showing the Zircaloy-4/SUS 316 interfacial structure of the PST when quenched to room temperature after being held at 900°C for 1 hour.
Transmission electron microscopy (TEM) cross-sectional image showing the boundary structure of Zircaloy-4/SUS 316 PST quenched to room temperature after being held at 900 °C for 1 h.
Application of the 2-D Trefftz Method for Identification of Flow Boiling Heat Transfer
Experimental Facility
Two pressure sensors (Kobold 0–2.5 bar) were placed at the inlet and outlet of the channel. Photographs of the observed two-phase flow structures were taken with a high-speed video camera with a recording speed of 7000 fps. Lab is the void fraction for a single elongated bubble, Llb is the bubble length, composed of the length of an ellipsoidal cylinder and two half-ellipsoids.
Lab is the void for a single elongated bubble, Llb, ije length of the bubble, composed of the length of the ellipsoid cylinder and one semi-ellipsoid.
Mathematical Model and Numeric Solution
Next, by combining four T-complete functions for Equation (20) and specific solution of Equation (11), the field of the fluid temperature was found. Fluid flowing in the minichannel significantly reduces the temperature of the copper block over the contact area, Figure 12. Variation of the heat transfer coefficient for the flowing two-phase mixture is shown in Figure 13 as a function of the distance from the minichannel inlet.
Uncertainties of the experimental parameters determined in the study [2] were applied to calculate the mean relative error (MRE) of the heat transfer coefficient α(x).
A Study on the Application Possibility of the Vehicle Air Conditioning System Using Vortex Tube
Experimental Approach 1. Principle of Vortex Tube
The variation of temperature according to the pressure in the vortex tube device and the number of nozzles of the generator is investigated. In the case of Taoc (◦C), the temperature was measured by comparing the air flow rate at low temperature (yc) of the flow. The value of ΔTac (◦C) was also measured using the low temperature airflow ratio (yc), and the temperature difference was similar to Taoc (◦C).
Numerical investigations of compressible flow and energy dissipation in the Ranque–Hilsch vortex tube. Int.
MDPI
