Water is pumped from a lower reservoir to a higher reservoir by a pump that prov

glamrockqueen7

glamrockqueen7

Answered question

2021-10-23

Water is pumped from a lower reservoir to a higher reservoir by a pump that provides 20 kW of shaft power. The free surface of the upper reservoir is 45 m higher than that of the lower reservoir. If the flow rate of water is measured to be 0.03m3s, determine mechanical power that is converted to thermal energy during this process due to frictional effects.

Answer & Explanation

pattererX

pattererX

Skilled2021-10-24Added 95 answers

We must first determine the pace at which the mechanical energy of the water is increasing:
Emech,  in  =mgh 
=ρVgh 
=1000kgm30.03m3s9.81ms245m 
=13.2kW 
The power dissipated is then determined by the difference between the invested power and the rate of energy increase:
Emech,  lost  =Wmech,in  Emech,  in 
=(2013.2)kW 
=6.8kW 
Result: 
Emech,  lost  =6.8kW

user_27qwe

user_27qwe

Skilled2023-06-10Added 375 answers

Step 1:
The mechanical power provided by the pump is 20 kW. We need to convert this power to the flow rate of water using the equation:
Pmech=ρgQH
where:
- Pmech is the mechanical power provided by the pump (20 kW)
- ρ is the density of water (taken as 1000kg/m3)
- g is the acceleration due to gravity (taken as 9.8m/s2)
- Q is the flow rate of water (0.03m3/s)
- H is the height difference between the upper and lower reservoirs (45 m)
Solving for Pmech, we have:
20kW=(1000kg/m3)·(9.8m/s2)·(0.03m3/s)·45m
Step 2:
Now, we can calculate the value of Pmech:
Pmech=(1000kg/m3)·(9.8m/s2)·(0.03m3/s)·45m=13230W
Therefore, the mechanical power converted to thermal energy due to frictional effects during this process is 13,230 W or 13.23 kW.
karton

karton

Expert2023-06-10Added 613 answers

Answer:
112300W
Explanation:
The mechanical power provided by the pump is 20 kW, which we can express as Pmech=20kW.
The flow rate of water is given as Q=0.03(m3s).
The height difference between the two reservoirs is 45 m, denoted as h=45m.
We can calculate the potential energy change of the water using the formula PE=m·g·h, where m is the mass of water and g is the acceleration due to gravity.
The mass of water can be calculated using the flow rate and the density of water, denoted as ρ=1000(kgm3).
So, m=ρ·Q.
The potential energy change can then be expressed as PE=(ρ·Q)·g·h.
The mechanical power can be related to the potential energy change by the equation Pmech=dPEdt.
Therefore, the power converted to thermal energy due to frictional effects, denoted as Pthermal, can be calculated as Pthermal=PmechdPEdt.
Substituting the given values into the equations, we can calculate Pthermal.
Let's proceed with the calculations:
Pmech=20kWQ=0.03(m3s)h=45mρ=1000(kgm3)
First, we calculate the potential energy change:
PE=(ρ·Q)·g·h=(1000(kgm3)·0.03(m3s))·9.8(ms2)·45m=132300W
Now, we can calculate the power converted to thermal energy:
Pthermal=PmechdPEdt=20kWd(132300W)dt=20kW132300W/s=112300W
Therefore, the mechanical power converted to thermal energy due to frictional effects is 112300W.
alenahelenash

alenahelenash

Expert2023-06-10Added 556 answers

Let's denote the flow rate of water as Q=0.03m3/s and the height difference between the reservoirs as h=45m. The mechanical power provided by the pump is Pmech=20kW.
The potential energy change of the water is given by the formula:
ΔPE=m·g·h
where m is the mass of water and g is the acceleration due to gravity.
Since the flow rate is given, we can find the mass of water per second using the formula:
m=Q·ρ where ρ is the density of water.
Substituting the expression for m into the potential energy formula, we have:
ΔPE=(Q·ρ)·g·h
Now, let's find the power converted to thermal energy due to frictional effects. The total power provided by the pump is equal to the sum of the power used to increase the potential energy and the power converted to thermal energy:
Ptotal=Pmech=PPE+Pthermal
The power used to increase the potential energy can be calculated as:
PPE=ΔPE/t where t is the time taken to pump the water from the lower reservoir to the higher reservoir.
Finally, we can find the power converted to thermal energy as:
Pthermal=PtotalPPE
Now, let's calculate the values using the given data:
- Flow rate: Q=0.03m3/s
- Height difference: h=45m
- Mechanical power: Pmech=20kW
The density of water, ρ, is approximately 1000kg/m3, and the acceleration due to gravity, g, is approximately 9.8m/s2.
First, let's calculate the potential energy change:
ΔPE=(Q·ρ)·g·h=(0.03m3/s·1000kg/m3)·(9.8m/s2)·45m
Substituting the values, we find:
ΔPE=13230W
Next, let's calculate the power used to increase the potential energy:
PPE=ΔPE/t
Since the time t is not given, we cannot calculate the exact value of PPE without it.
Finally, let's find the power converted to thermal energy:
Pthermal=PtotalPPE
Substituting the given mechanical power Pmech=20kW and the calculated PPE, we can find Pthermal.

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