As permanent space stations increase in size. there is an attendant increase in the amount of electrical power they dissipate. To keep station compartment temperatures from exceeding prescribed limits, it is necessary to transfer the dissipated heat to space. A novel heat rejection scheme that has been proposed for thispurpose is termed a Liquid Droplet Radiator (LDR). heat is first transferred to a high vacuum oil. which is then injected into outer space as a stream of small droplets. The stream is allowed to traverse a distance L, over which it cools by radiating energy to outer space at absolute zero temperature. The droplets are then collected and routed back to the space station. Consider conditions for which droplets of emissivity ε = 0.95 and diameter D = 0.5 mm are injected at a temperature of T i = 500 K and a velocity of V = 0.1 m/s . Properties of the oil are ρ = 885 k g / m 3 , c = 1900 J/kg ⋅ K, and k = 0.145 W/m ⋅ K . Assuming each drop to radiate to deep space at T sur = 0 K, determine the distance L required for the droplets to impact the collector at a final temperature of T f = 300 K . What is the amount of thermal energy rejected by each droplet?
As permanent space stations increase in size. there is an attendant increase in the amount of electrical power they dissipate. To keep station compartment temperatures from exceeding prescribed limits, it is necessary to transfer the dissipated heat to space. A novel heat rejection scheme that has been proposed for thispurpose is termed a Liquid Droplet Radiator (LDR). heat is first transferred to a high vacuum oil. which is then injected into outer space as a stream of small droplets. The stream is allowed to traverse a distance L, over which it cools by radiating energy to outer space at absolute zero temperature. The droplets are then collected and routed back to the space station. Consider conditions for which droplets of emissivity ε = 0.95 and diameter D = 0.5 mm are injected at a temperature of T i = 500 K and a velocity of V = 0.1 m/s . Properties of the oil are ρ = 885 k g / m 3 , c = 1900 J/kg ⋅ K, and k = 0.145 W/m ⋅ K . Assuming each drop to radiate to deep space at T sur = 0 K, determine the distance L required for the droplets to impact the collector at a final temperature of T f = 300 K . What is the amount of thermal energy rejected by each droplet?
Solution Summary: The author calculates the amount of thermal energy rejected by each droplet by separating variables and integrating.
As permanent space stations increase in size. there is an attendant increase in the amount of electrical power they dissipate. To keep station compartment temperatures from exceeding prescribed limits, it is necessary to transfer the dissipated heat to space. A novel heat rejection scheme that has been proposed for thispurpose is termed a Liquid Droplet Radiator (LDR). heat is first transferred to a high vacuum oil. which is then injected into outer space as a stream of small droplets. The stream is allowed to traverse a distance L, over which it cools by radiating energy to outer space at absolute zero temperature. The droplets are then collected and routed back to the space station.
Consider conditions for which droplets of emissivity
ε
=
0.95
and diameter
D
=
0.5
mm
are injected at a temperature of
T
i
=
500
K
and a velocity of
V
=
0.1
m/s
.
Properties of the oil are
ρ
=
885
k
g
/
m
3
,
c
=
1900
J/kg
⋅
K,
and
k
=
0.145
W/m
⋅
K
.
Assuming each drop to radiate to deep space at
T
sur
=
0
K,
determine the distance L required for the droplets to impact the collector at a final temperature of
T
f
=
300
K
.
What is the amount of thermal energy rejected by each droplet?
A cylinder 6”in diameter and 18”long is suspended horizontally in a largeroom. The air and wall surfaces of the room are at a temperature of 60 °Fwhile the surface temperature of the cylinder is 440 °F. Compute (a) thesurface coefficient due to free convection, (b) the heat transferred by freeconvection (neglecting the end areas), (c) the surface coefficient due toradiation if the surface emissivity is 0.75, and (d) the total heattransferred by free convection and radiation (neglecting end areas)
A thermal energy storage unit consists of a large rectangular channel, which is wellinsulated on its outer surface and encloses alternating layers of the storage material andthe flow passage.Each layer of the storage material is an aluminum slab of width ? = 0.05 m, which is at aninitial temperature of 25°C. Consider conditions for which the storage unit is charged bypassing a hot gas through the passages, with the gas temperature and the convectioncoefficient assumed to have constant values of ?∞ = 600°C and ℎ = 100 W/m2– Kthroughout the channel. How long will it take to achieve 75% of the maximum possibleenergy storage? What is the temperature of the aluminum at this time?
A common arrangement for heating a large surface area is to move warm air through rectangular ducts below the surface. The ducts are square and located midway between the top and bottom surfaces that are exposed to room air and insulated, respectively. For the condition when the floor and duct temperatures are 30C and 80C, respectively, and the thermal conductivity of concrete is 1.4 W/m*K, calculate the heat rate from each duct, per unit length of the duct. Use a grid spacing with delta x = 2*(delta y), where delta y = 0.125L and L=150mm.
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.