You are in charge of keeping the drinks cold for a picnic. You have a Styrofoam

Question

You are in charge of keeping the drinks cold for a picnic. You have a Styrofoam box that is filled with cola, water and you plan to put some 0 C ice in it. Your task it to buy enough ice to put in the box at 6AM so that the temperature stays at 0 C until the picnic starts at 6PM. You don't want to buy too mych ice because that means that you'll have less money to spend on food and other picnic items. You plan on keeping cold six 6-liter bottles of cola. How much ice will you need?

Today will be beautifully sunny: a perfect day for a picnic. The temperature will start out at 10 C at 6AM and then the temperature will steadily incfrease, reaching 35 C at 6PM. It will be partially cloudy with a mild breeze from the west.

Assume:

1. coolers dimensions are .4m x .4m x .4m

2. thickness of coller is 2cm

3. temperature of cola when put in cooler is 20 C

4. Treat cola as water (Specific heat and density)

Explanation / Answer

solution:

Assume:

1. coolers dimensions are .4m x .4m x .4m

2. thickness of coller is 2cm

3. temperature of cola when put in cooler is 20 C

4. Treat cola as water (Specific heat and density)

surface area for coolers to heat flow =.4*.4+.4*.4+.4*.4 =.48m2

Q = [ k * A * dT / d ]

k = thermal conductivity styrofoam is 0.01w/m/C
A = area 0.48 m2
d = thickness 0.02m
dT = 20 - 0 = 20C
Q = 4.8 watt ------- calculated

1w = 1J/s
H = (4.8j/s)(3600s/h)(12h/) = 207,360J

ice heat of fusion is 334J/g

m = 207,360 / 334 = 620.8 g <=== ans

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