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Undergrad1147
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Homework Statement
You've been asked to draw a P&ID for a water heating system. 20 tonne/hr of water is to be pumped from the atmosphere into a heat exchanger at 1.6 MPa. Steam is being used to heat the water to 145 C. The heated fluid is then stored in a vessel, which is designed to hold 4 minutes of flow. Show all your calculations.
Homework Equations
Where ##Q## is the volumetric flow rate:
1)##Q = Av## where ##A## is the cross sectional area of the pipe and ##v## is the velocity of the fluid through the pipe.
2)##Q = \frac{ \dot{m}}{\rho} ## where ##\dot{m}## is the mass flow rate and ##\rho## is the density of the fluid.
3)The speed of water through pipe can be approximated as 2 m/s.
The Attempt at a Solution
Well, 20 tonnes/hr is equal to 20(1000)/60(60) kg/s. Thus: $$\dot{m_{water}} = 5.55 kg/s$$
Dividing this by the density of water, the value of ##Q_{water}## was found to be 5.55 x ##10^{-3}## m^3/s.
Using this, the value of the pipe diameter can be calculated to be 0.059 metres by using equation (1). Now, I was wondering, does the heating by the steam affect the value of the flow rate out of the heat exchanger? If not, the capacity of the vessel can easily be calculated by multiplying the surge time (in seconds) by the flow rate.
Finally, how do I incorporate the values of temperature and pressure into my calculation? I'm not really sure what they're required for.
Also, how would I go about sizing the size of the pipe used to deliver the steam? Or is that even possible with the information required? Thanks in advance and if you need any clarification on the question, let me know.
Also, this is my first post, but I still know that I won't be told the answer. Just a help in the right direction would be handy. Thanks.
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