PV Gap

Eddie Said:

Heat transfer for Solar Application (senior design)?

We Answered:

This is not my expertise, but let me give it a try. I'll pick some arbitrary numbers, as it is easier to do an actual example.

If the radius of the pipe is 1 cm, then the cross-sectional area is 3e-4 m², and if the length is 5 meters,the volume is 15e-4 m³. Assuming the working fluid is water....

Take 5 meters of length and calculate the thermal power into that pipe from the sun and the reflectors. Assume this is 500 watts, 500 joules per second.

specific heat of water is 4186 J/kgC. In 1 second, 500 joules are transferred, causing a ?T temperature change. You can calculate the mass of water in kg from the size of the pipe, and the density of water.

m = 998 kg/m³ x 15e-4 m³ = 1.5 kg

500J = 4186 J/kgC x 1.5kg x ?T
?T = 0.08ºC.

Now we need the flow rate, in m³/s. Assume 0.0001 m³/s.

5e-4 m³ / 0.0001 m³/s = 5 s, which means the water is changed every 5 seconds. In this case, it means the ?T will be 5x the above number, since that assumed 1 sec. So ?T = 0.08ºC x 5 = 0.4ºC

But you want 70ºC change, 70/0.4 higher or 175 times bigger. That means the pipe has to be that much longer or 5 x 175 or 875 meters.

Some of my numbers are way off, but hopefully you will get the ides.


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Gladys Said:

How to spread solar street lamp with LPS bulbs ?

We Answered:

Hallo Its nice you r working on green revolution.
I had work experience of over 25 years in marketing. I can help u as i worked for one of the largest lighting co. producing lighting products HID lamps MV & SV and fixtures for ftl lighting with open type and electronic ballast.
If intrested i can arrange for tie up for your products. recently i had visited a Windmill farm having over 3000 intallations.
thanks.

Joe Said:

do you agree with the BNP?

We Answered:

yes i agree with the BNP they are the only hope this country as because the way things are going now we will become a third world country in 20 years or less

Pedro Said:

question about specific heats of metals (physics)?

We Answered:

we know specific heat is the amount of heat needed to increase the temperature by 1K of a 1Kg substance.
specific heat must be lower.

Gertrude Said:

Homework Assignment Questions, science class help please?

We Answered:

lmao im in that class ;) quiz on tuesday?

a)
you have 36 ppb Hg which is 36 * 10 ^-6 g/L and a discharge of 4 m^3 /s

you know that m^3 is 1 L, so it's discharge of 4 L/s

your givens are:
36 * 10^-6 g/L
4 L/s
and you are given seconds(1 day), 1 day = 24 hours = (24*60)minutes = (24*60*60)seconds

can you do the rest?

Leo Said:

Pleaseeeeeeeeee Helllppppppppppppppp?

We Answered:

All you need to know ... Oil is running out fast; wind and thermal are unpredictable; most other energy sources add pollution to the planet so they hurt life; Solar is clean and requires no servicing. Go Figure.