The final temperature of steam in the tank is 375/V1°C, and the final mass of steam in the tank is 1041.26 V1 kg.
The given problem is related to the thermodynamics of a closed system. Here, we are given an insulated, rigid tank whose volume is 0.5 m³, and it is connected to a large vessel holding steam at 40 bar and 400°C. The tank is initially evacuated. The valve is opened only as long as required to fill the tank with steam to a pressure of 30 bar. Our objective is to determine the final temperature of the steam in the tank and the final mass of the steam in the tank. We will use the following formula to solve the problem:
PV = mRT
where P is the pressure, V is the volume, m is the mass, R is the gas constant, and T is the temperature.
The gas constant R = 0.287 kJ/kg K for dry air. Here, we assume steam to behave as an ideal gas because it is at high temperature and pressure. Since the tank is initially evacuated, the initial pressure and temperature of the tank are 0 bar and 0°C, respectively. The final pressure of the steam in the tank is 30 bar. Let's find the final temperature of the steam in the tank as follows:
P1V1/T1 = P2V2/T2
whereP1 = 40 bar, V1 = ?, T1 = 400°CP2 = 30 bar, V2 = 0.5 m³, T2 = ?
Rearranging the above formula, we get:
T2 = P2V2T1/P1V1T2 = 30 × 0.5 × 400/(40 × V1)
T2 = 375/V1
The final temperature of steam in the tank is 375/V1°C.
Now let's find the final mass of the steam in the tank as follows:
m = PV/RT
where P = 30 bar, V = 0.5 m³, T = 375/V1R = 0.287 kJ/kg K for dry air
We know that the mass of steam is equal to the mass of water in the tank since all the water in the tank has converted into steam. The density of water at 30 bar is 30.56 kg/m³. Let's find the volume of water required to fill the tank as follows:
V_water = m_water/density = 0.5/30.56 = 0.0164 m³
where m_water is the mass of water required to fill the tank. Since all the water in the tank has converted into steam, the final mass of steam in the tank is equal to m_water. Let's find the final mass of steam in the tank as follows:
m = PV/RT = 30 × 10^5 × 0.5/(0.287 × 375/V1) = 1041.26 V1 kg
The final mass of steam in the tank is 1041.26 V1 kg.
Therefore, the final temperature of steam in the tank is 375/V1°C, and the final mass of steam in the tank is 1041.26 V1 kg.
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Design a excel file of an hydropower turgo turbine in Sizing and Material selection.
Excel file must calculate the velocity of the nozel, diameter of the nozel jet, nozzle angle, the runner size of the turgo turbine, turbine blade size, hub size, fastner, angular velocity,efficiency,generator selection,frequnecy,flowrate, head and etc.
(Note: File must be in execl file with clearly formulars typed with all descriptions in the sheet)
Designing an excel file for a hydropower turbine (Turgo turbine) involves calculating different values that are essential for its operation. These values include the velocity of the nozzle, diameter of the nozzle jet, nozzle angle, runner size of the turbine, turbine blade size, hub size, fastener, angular velocity, efficiency, generator selection, frequency, flow rate, head, etc.
To create an excel file for a hydropower turbine, follow these steps:Step 1: Open Microsoft Excel and create a new workbook.Step 2: Add different sheets to the workbook. One sheet can be used for calculations, while the others can be used for data input, output, and charts.Step 3: On the calculation sheet, enter the formulas for calculating different values. For instance, the formula for calculating the velocity of the nozzle can be given as:V = (2 * g * H) / (√(1 - sin²(θ / 2)))Where V is the velocity of the nozzle, g is the acceleration due to gravity, H is the head, θ is the nozzle angle.Step 4: After entering the formula, label each column and row accordingly. For example, the velocity of the nozzle formula can be labeled under column A and given a name, such as "Nozzle Velocity Formula".Step 5: Add a description for each formula entered in the sheet.
The explanation should be clear, concise, and easy to understand. For example, a description for the nozzle velocity formula can be given as: "This formula is used to calculate the velocity of the nozzle in a hydropower turbine. It takes into account the head, nozzle angle, and acceleration due to gravity."Step 6: Repeat the same process for other values that need to be calculated. For example, the formula for calculating the diameter of the nozzle jet can be given as:d = (Q / V) * 4 / πWhere d is the diameter of the nozzle jet, Q is the flow rate, and V is the velocity of the nozzle. The formula should be labeled, given a name, and described accordingly.Step 7: Once all the formulas have been entered, use the data input sheet to enter the required data for calculation. For example, the data input sheet can contain fields for flow rate, head, nozzle angle, etc.Step 8: Finally, use the data output sheet to display the calculated values. You can also use charts to display the data graphically. For instance, you can use a pie chart to display the percentage efficiency of the turbine. All the sheets should be linked correctly to ensure that the data input reflects on the calculation sheet and output sheet.
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A mesh of 4-node pyramidic elements (i.e. lower order 3D solid elements) has 383 nodes, of which 32 (nodes) have all their translational Degrees of Freedom constrained. How many Degrees of Freedom of this model are constrained?
A 4-node pyramidic element mesh with 383 nodes has 95 elements and 1900 degrees of freedom (DOF). 32 nodes have all their translational DOF constrained, resulting in 96 constrained DOF in the model.
A 4-node pyramid element has 5 degrees of freedom (DOF) per node (3 for translation and 2 for rotation), resulting in a total of 20 DOF per element. Therefore, the total number of DOF in the model is:
DOF_total = 20 * number_of_elements
To find the number of elements, we need to use the information about the number of nodes in the mesh. For a pyramid element, the number of nodes is given by:
number_of_nodes = 1 + 4 * number_of_elements
Substituting the given values, we get:
383 = 1 + 4 * number_of_elements
number_of_elements = 95
Therefore, the total number of DOF in the model is:
DOF_total = 20 * 95 = 1900
Out of these, 32 nodes have all their translational DOF constrained, which means that each of these nodes has 3 DOF that are constrained. Therefore, the total number of DOF that are constrained is:
DOF_constrained = 32 * 3 = 96
Therefore, the number of Degrees of Freedom of this model that are constrained is 96.
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Compute the Fourier Series decomposition of a square waveform with 90% duty cycle
The Fourier series decomposition of the square waveform with a 90% duty cycle is given by: f(t) = (a0/2) + ∑[(an * cos((2πnt)/T)) + (bn * sin((2πnt)/T))]
The Fourier series decomposition for a square waveform with a 90% duty cycle:
Definition of the Square Waveform:
The square waveform with a 90% duty cycle is defined as follows:
For 0 ≤ t < T0.9 (90% of the period), the waveform is equal to +1.
For T0.9 ≤ t < T (10% of the period), the waveform is equal to -1.
Here, T represents the period of the waveform.
Fourier Series Coefficients:
The Fourier series coefficients for this waveform can be computed using the following formulas:
a0 = (1/T) ∫[0 to T] f(t) dt
an = (2/T) ∫[0 to T] f(t) cos((2πnt)/T) dt
bn = (2/T) ∫[0 to T] f(t) sin((2πnt)/T) dt
where a0, an, and bn are the Fourier coefficients.
Computation of Fourier Coefficients:
For the given square waveform with a 90% duty cycle, we have:
a0 = (1/T) ∫[0 to T] f(t) dt = 0 (since the waveform is symmetric around 0)
an = 0 for all n ≠ 0 (since the waveform is symmetric and does not have cosine terms)
bn = (2/T) ∫[0 to T] f(t) sin((2πnt)/T) dt
Computation of bn for n = 1:
We need to compute bn for n = 1 using the formula:
bn = (2/T) ∫[0 to T] f(t) sin((2πt)/T) dt
Breaking the integral into two parts (corresponding to the two regions of the waveform), we have:
bn = (2/T) [∫[0 to T0.9] sin((2πt)/T) dt - ∫[T0.9 to T] sin((2πt)/T) dt]
Evaluating the integrals, we get:
bn = (2/T) [(-T0.9/2π) cos((2πt)/T)] from 0 to T0.9 - (-T0.1/2π) cos((2πt)/T)] from T0.9 to T
bn = (2/T) [(T - T0.9)/2π - (-T0.9)/2π]
bn = (T - T0.9)/π
Fourier Series Decomposition:
The Fourier series decomposition of the square waveform with a 90% duty cycle is given by:
f(t) = (a0/2) + ∑[(an * cos((2πnt)/T)) + (bn * sin((2πnt)/T))]
However, since a0 and an are 0 for this waveform, the decomposition simplifies to:
f(t) = ∑[(bn * sin((2πnt)/T))]
For n = 1, the decomposition becomes:
f(t) = (T - T0.9)/π * sin((2πt)/T)
This represents the Fourier series decomposition of the square waveform with a 90% duty cycle, including the computation of the Fourier coefficients and the final decomposition expression for the waveform.
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I have found a research study online with regards to PCM or Phase changing Material, and I can't understand and visualize what PCM is or this composite PCM. Can someone pls help explain and help me understand what these two composite PCMs are and if you could show images of a PCM it is really helpful. I haven't seen one yet and nor was it shown to us in school due to online class. pls help me understand what PCM is the conclusion below is just a part of a sample study our teacher gave to help us understand though it was really quite confusing, Plss help
. Conclusions
Two composite PCMs of SAT/EG and SAT/GO/EG were prepared in this article. Their thermophysical characteristic and solar-absorbing performance were investigated. Test results indicated that GO showed little effect on the thermal properties and solar absorption performance of composite PCM. However, it can significantly improve the shape stability of composite PCM. The higher the density is, the larger the volumetric heat storage capacity. When the density increased to 1 g/ cm3 , SAT/EG showed severe leakage while SAT/GO/EG can still keep the shape stability. A novel solar water heating system was designed using SAT/GO/EG (1 g/cm3 ) as the solar-absorbing substance and thermal storage media simultaneously. Under the real solar radiation, the PCM gave a high solar-absorbing efficiency of 63.7%. During a heat exchange process, the temperature of 10 L water can increase from 25 °C to 38.2 °C within 25 min. The energy conversion efficiency from solar radiation into heat absorbed by water is as high as 54.5%, which indicates that the novel system exhibits great application effects, and the composite PCM of SAT/GO/EG is very promising in designing this novel water heating system.
PCM stands for Phase Changing Material, which is a material that can absorb or release a large amount of heat energy when it undergoes a phase change.
A composite PCM, on the other hand, is a mixture of two or more PCMs that exhibit improved thermophysical properties and can be used for various applications. In the research study mentioned in the question, two composite PCMs were investigated: SAT/EG and SAT/GO/EG. SAT stands for stearic acid, EG for ethylene glycol, and GO for graphene oxide.
These composite PCMs were tested for their thermophysical characteristics and solar-absorbing performance. The results showed that GO had little effect on the thermal properties and solar absorption performance of composite PCM, but it significantly improved the shape stability of the composite PCM.
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4) Disc brakes are used on vehicles of various types (cars, trucks, motorcycles). The discs are mounted on wheel hubs and rotate with the wheels. When the brakes are applied, pads are pushed against the faces of the disc causing frictional heating. The energy is transferred to the disc and wheel hub through heat conduction raising its temperature. It is then heat transfer through conduction and radiation to the surroundings which prevents the disc (and pads) from overheating. If the combined rate of heat transfer is too low, the temperature of the disc and working pads will exceed working limits and brake fade or failure can occur. A car weighing 1200 kg has four disc brakes. The car travels at 100 km/h and is braked to rest in a period of 10 seconds. The dissipation of the kinetic energy can be assumed constant during the braking period. Approximately 80% of the heat transfer from the disc occurs by convection and radiation. If the surface area of each disc is 0.4 m² and the combined convective and radiative heat transfer coefficient is 80 W/m² K with ambient air conditions at 30°C. Estimate the maximum disc temperature.
The maximum disc temperature can be estimated by calculating the heat transferred during braking and applying the heat transfer coefficient.
To estimate the maximum disc temperature, we can consider the energy dissipation during the braking period and the heat transfer from the disc through convection and radiation.
Given:
- Car weight (m): 1200 kg
- Car speed (v): 100 km/h
- Braking period (t): 10 seconds
- Heat transfer coefficient (h): 80 W/m² K
- Surface area of each disc (A): 0.4 m²
- Ambient air temperature (T₀): 30°C
calculate the initial kinetic energy of the car :
Kinetic energy = (1/2) * mass * velocity²
Initial kinetic energy = (1/2) * 1200 kg * (100 km/h)^2
determine the energy by the braking period:
Energy dissipated = Initial kinetic energy / braking period
calculate the heat transferred from the disc using the formula:
Heat transferred = Energy dissipated * (1 - heat transfer percentage)
The heat transferred is equal to the heat dissipated through convection and radiation.
Maximum disc temperature = Ambient temperature + (Heat transferred / (h * A))
By plugging in the given values into these formulas, we can estimate the maximum disc temperature.
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