A 2-m3insulated rigid tank contains 3.2 kg of carbon dioxide at 120 kPa.Paddle-wheel work is done on the system until the pressure in the tank rises to 180kPa. Determine the entropy change in the carbon dioxide during this process. Assumeconstant specific heat and room temperature at 300 K
Answers
Answer:
The change in entropy is found to be 0.85244 KJ/k
Explanation:
In order to solve this question, we first need to find the ration of temperature for both state 1 and state 2. For that, we can use Charles' law. Because the volume of the tank is constant.
P1/T1 = P2/T2
T2/T1 = P2/P1
T2/T1 = 180 KPa/120KPa
T2/T1 = 1.5
Now, the change in entropy is given as:
ΔS = m(s2 - s1)
where,
s2 = Cv ln(T2/T1)
s1 = R ln(V2/V1)
ΔS = change in entropy
m = mass of CO2 = 3.2 kg
Therefore,
ΔS = m[Cv ln(T2/T1) - R ln(V2/V1)]
Since, V1 = V2, therefore,
ΔS = mCv ln(T2/T1)
Cv at 300 k for carbondioxide is 0.657 KJ/Kg.K
Therefore,
ΔS = (3.2 kg)(0.657 KJ/kg.k) ln(1.5)
ΔS = 0.85244 KJ/k
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For steels, we can assume the endurance limit measured by rotating beam tests is the 50% of the ultimate tensile strength (UTS) as long as the UTS is equal to or less than 200 ksi (1400 MPa).True/False
Answers
Answer:
T = 858.25 s
Explanation:
Given data:
Reheat stage for a 100-mm-thick steel plate ( 7830 kg/m3, c 550 J/kg K, k 48 W/m K),
initial uniform temperature ( Ti ) = 200 c
Final temperature = 550 c
convection coefficient = 250 w/m^2 k
products combustion temp = 800 c
calculate how long the plate should be left in the furnace ( to attain 550 c )
first calculate/determine the Fourier series Number ( Fo )
= 0.4167 =
therefore Fo = 3.8264
Now determine how long the plate should be left in the furnace
Fo =
k = 48
p = 7830
L = 0.1
Input the values into the relation and make t subject of the formula
hence t = 858.25 s
Answers
Answer:
b). False
Explanation:
Lumped body analysis :
Lumped body analysis states that some bodies during heat transfer process remains uniform at all times. The temperature of these bodies is a function of temperature only. Therefor the heat transfer analysis based on such idea is called lumped body analysis.
Biot number is a dimensionless number which governs the heat transfer rate for a lumped body. Biot number is defined as the ratio of the convection transfer at the surface of the body to the conduction inside the body. the temperature difference will be uniform only when the Biot number is nearly equal to zero.
The lumped body analysis assumes that there exists a uniform temperature distribution within the body. This means that the conduction heat resistance should be zero. Thus the lumped body analysis is exact when biot number is zero.
In general it is assume that for a lumped body analysis, Biot number 0.1
Therefore, the smaller the Biot number, the more exact is the lumped system analysis.
Answers
Answer:
I want to believe the program is to be written in java and i hope your question is complete. The code is in the explanation section below
Explanation:
import java.util.Date;
public interface Downloadable {
//abstract methods
public String getUrl();
public Date getLastDownloadDate();
}
Answers
Answer:
The correct answer is C) Trimetric
Explanation:
The most suitable answer is a trimetric projection because, in this type of projection, we see that the projection of the three angles between the axes are not equal. Therefore, to generate a trimetric projection of an object, it is necessary to have three separate scales.
Answers
Answer:
Concentration = 10.33 kg/m³
Explanation:
We are given;
Mass of solids; 10,000 kg
Volume; V = 440,000 L = 440 m³
Rate at which water is pumped out = 40,000 liter/h
Thus, at the end of 5 hours we amount of water that has been replaced with fresh water is = 40,000 liter/h x 5 hours = 200,000 L = 200 m³
Now, since the tank is perfectly mixed, therefore we can calculate a ratio of fresh water to sewage water as;
200m³/440m³ = 5/11
Thus, the amount left will be calculated by multiplying that ratio by the amount of solids;
Thus,
Amount left; = 10000 x (5/11) = 4545 kg
The concentration would be calculated by:
Concentration = amount left/initial volume
Thus,
Concentration = 4545/440 = 10.3 kg/m³
Answers
Answer:
Conduction is a heat transfer mechanism. It is the dominant heat transfer mechanism in solids and it involves the vibration of the molecules of the solid. As heat is transfered to one end of the solid, the molecules at that end start to vibrate and in this process, collides with the adjacent molecules setting it to vibrate too. Also free electrons around the solid atoms (especially in metals) contribute to this heat flow. The continuous vibration is transfered from molecule to molecule gradually along the solid until the average kinetic energy (a measure of temperature) of the molecules along the metal has increased.
Convection is the dominant heat transfer mechanism in fluids, it involves the complete movement of the fluid molecule from a hot spot in the fluid to a cooler spot in the fluid. For convectional movement to occur, the molecules must first come in contact with the heat and absorb the heat first by conduction. As the heat increases, the fluid molecules break from just vibrating about a fixed point to moving completely to a cooler spot due to buoyant forces (due to the difference in density of hot and cooler fluid molecules). This clearly point out the fact that convectional heat transfer is first conduction, and then complete later flow of the fluid molecules.