Answer:
-50.005 KJ
Explanation:
Mass flow rate = 0.147 KJ per kg
mass= 10 kg
Δh= 50 m
Δv= 15 m/s
W= 10×0.147= 1.47 KJ
Δu= -5 kJ/kg
ΔKE + ΔPE+ ΔU= Q-W
0.5×m×(30^2- 15^2)+ mgΔh+mΔu= Q-W
Q= W+ 0.5×m×(30^2- 15^2) +mgΔh+mΔu
= 1.47 +0.5×1/100×(30^2- 15^2)-9.7×50/1000-50
= 1.47 +3.375-4.8450-50
Q=-50.005 KJ
Answer:
15.24°C
Explanation:
The quality of any heat pump pumping heat from cold to hot place is determined by its coefficient of performance (COP) defined as
![COP=\frac{Q_{in}}{W}](https://tex.z-dn.net/?f=COP%3D%5Cfrac%7BQ_%7Bin%7D%7D%7BW%7D)
Where Q_{in} is heat delivered into the hot place, in this case, the house, and W is the work used to pump heat
You can think of this quantity as similar to heat engine's efficiency
In our case, the COP of our heater is
![COP_{heater} = \frac{\frac{4500\ kJ}{3600\ s} *(T_{house}-T_{out})}{4\ kW}](https://tex.z-dn.net/?f=COP_%7Bheater%7D%20%3D%20%5Cfrac%7B%5Cfrac%7B4500%5C%20kJ%7D%7B3600%5C%20s%7D%20%2A%28T_%7Bhouse%7D-T_%7Bout%7D%29%7D%7B4%5C%20kW%7D)
Where T_{house} = 24°C and T_{out} is temperature outside
To achieve maximum heating, we will have to use the most efficient heat pump, and, according to the second law of thermodynamics, nothing is more efficient that Carnot Heat Pump
Which has COP of:
![COP_{carnot}=\frac{T_{house}}{T_{house}-T_{out}}](https://tex.z-dn.net/?f=COP_%7Bcarnot%7D%3D%5Cfrac%7BT_%7Bhouse%7D%7D%7BT_%7Bhouse%7D-T_%7Bout%7D%7D)
So we equate the COP of our heater with COP of Carnot heater
![\frac{1.25 *(T_{house}-T_{out})}{4}=\frac{T_{house}}{T_{house}-T_{out}}](https://tex.z-dn.net/?f=%5Cfrac%7B1.25%20%2A%28T_%7Bhouse%7D-T_%7Bout%7D%29%7D%7B4%7D%3D%5Cfrac%7BT_%7Bhouse%7D%7D%7BT_%7Bhouse%7D-T_%7Bout%7D%7D)
Rearrange the equation
![\frac{1.25}{4}(24-T_{out})^2-24=0](https://tex.z-dn.net/?f=%5Cfrac%7B1.25%7D%7B4%7D%2824-T_%7Bout%7D%29%5E2-24%3D0)
Solve this simple quadratic equation, and you should get that the lowest outdoor temperature that could still allow heat to be pumped into your house would be
15.24°C
Answer:
Explanation:
Ohms Law I=E/R (resistive requires no power factor correction)
150/25= 6 amps
Answer:
combining scientific knowledge, careful reasoning, and artistic invention in a flexible approach to problem-solving
Explanation:
Answer:
It is best to soak the new lifters in engine oil overnight in order to build a car engine from scratch, regardless of its length. Ensure all rings of the pistons are installed correctly. You should flip the block over and carefully install the top half of the main rod and bearing parts. Get the block out of your way and flip it over again. By flipping over the block, you’ll see the full effect. Ensure that the lifters are installed correctly.
Explanation: