Specific Heat Question

[Sailor Senshi Dermystify]

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The total area of the Hubble telescope exposed to the sun is 70 000 m2. The rate of solar energy incident on the telescope is 120 W m-2. If a channel covering the entire exposed surface contains water and the temperature of the water must rise by at least 10 oC in order to keep the telescope cool, at what approximate rate must the water be made to flow assuming that energy transfer is instantaneous?

Specific heat capacity of water = 4.2 J g-1 oC-1
Density of water = 1000 kg m-3


They said to find the rate you will multiply, 70, 000 X 120 but I want to know what equation is this from to find the rate with the area.

Thanks

 

[LoLCareerGoals]

It is common sense unit matching equation. If 120W or 120 J/s is how many jules hit each sq m of the surface every second, then the entire surface must be absorbing 120 J/s-m2 x 70,000 m2 = 8,400,000 J/s or W.
That's the rate of heat hitting the entire surface. Now figure out how to balance that by the cooling process.

 

[indianjatt]

70000m^2x 120W/m^2 = 8400000 Watts (J/s) are incident on the hubble space craft. So the flow rate is the amount of volume/s of water. Since the water can only rise by 10 degrees C.

(4.184J/gC)(10)(mass water)=8400000 J
mass water = 200764.81 g of water. volume = .2 m^3. thus rate is .2m^3/s

 

[dmf2682]

The total area of the Hubble telescope exposed to the sun is 70 000 m2. The rate of solar energy incident on the telescope is 120 W m-2. If a channel covering the entire exposed surface contains water and the temperature of the water must rise by at least 10 oC in order to keep the telescope cool, at what approximate rate must the water be made to flow assuming that energy transfer is instantaneous?

Specific heat capacity of water = 4.2 J g-1 oC-1
Density of water = 1000 kg m-3


They said to find the rate you will multiply, 70, 000 X 120 but I want to know what equation is this from to find the rate with the area.

Thanks

Is that really what the question says?

70000 square meters is a lot of surface area. On the order of having a 100+m cube.

 

[Sailor Senshi Dermystify]

Is that really what the question says?

70000 square meters is a lot of surface area. On the order of having a 100+m cube.

Yes, I copied it verbatim from the website.


Thanks everyone for responding! 😀