- #1
hilly1989
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I have a problem here I am trying to solve for work. Does not need to be 100% accurate.
Apple slices are pushed through a bath of hot water to heat the outside of them for 30 seconds.
- Apple slice has an area of 3500mm² = 0.035m²
- Apple temperature is 3 degree cel
- Hot water temp = 53 deg cel. (kept constance from heat exchanger)
- Apple slices are heated for 30 seconds
- 82,300 slices per hour are processed.
- Thermal Conductivity of Apple = 0.5 W/(m K)
Im trying to find the Heat (energy transferred to the apples) - in other words, heat required by the heat exchanger to keep the bath at 53 degrees.
Here is my workings.
82,300 slices / (60*60) = 22.8 slices per second.
30 seconds bath time * 22.8 slices = 686 slices in bath at anyone time.
686 * 0.035 = 24m2 of surface area in the bath.
Q/t = K*A*(T1-T2)
Q/t= 0.5*24*50 = 600 J/s = 600W.
After looking on google, the formula I have above sometimes get divided with a distance. mainly when looking at heat losses through windows. distance = thickness. This makes sense as the units leaves me a with meter on the top. Q/t = W/(m K) * m2 * K,
So should I now divide the 600W by the average depth of a slice/2 (say 8mm)
giving me 75kW of heat being absorbed by the slices. Thats a lot of heat! (the Heat exchanger is capable of having upto 96kW provided to it, i think)
Thanks,
Anthony
Apple slices are pushed through a bath of hot water to heat the outside of them for 30 seconds.
- Apple slice has an area of 3500mm² = 0.035m²
- Apple temperature is 3 degree cel
- Hot water temp = 53 deg cel. (kept constance from heat exchanger)
- Apple slices are heated for 30 seconds
- 82,300 slices per hour are processed.
- Thermal Conductivity of Apple = 0.5 W/(m K)
Im trying to find the Heat (energy transferred to the apples) - in other words, heat required by the heat exchanger to keep the bath at 53 degrees.
Here is my workings.
82,300 slices / (60*60) = 22.8 slices per second.
30 seconds bath time * 22.8 slices = 686 slices in bath at anyone time.
686 * 0.035 = 24m2 of surface area in the bath.
Q/t = K*A*(T1-T2)
Q/t= 0.5*24*50 = 600 J/s = 600W.
After looking on google, the formula I have above sometimes get divided with a distance. mainly when looking at heat losses through windows. distance = thickness. This makes sense as the units leaves me a with meter on the top. Q/t = W/(m K) * m2 * K,
So should I now divide the 600W by the average depth of a slice/2 (say 8mm)
giving me 75kW of heat being absorbed by the slices. Thats a lot of heat! (the Heat exchanger is capable of having upto 96kW provided to it, i think)
Thanks,
Anthony