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Olegator [25]
3 years ago
14

Suppose a person (height of 1.8 m) walks in a room installed with a pyroelectric infrared (PIR) motion detector. The distance be

tween the person and the PIR detector is 5 m. The PIR detector sensor is 3 cm x 1 cm in size.
Estimate the radiated power at the surface of the sensor from the person. Assume that emissivity of human skin/fabric and sensor cap is 0.9. Assume that the person’s body temperature is 37°C and the temperature at the surface of PIR detector is at 18°C. Also assume that there is no radiated power loss through air and Fresnel lens. You can roughly estimate surface area of the person.
Engineering
1 answer:
3241004551 [841]3 years ago
8 0

Answer: b is your best option

Explanation:

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Consider a very long, cylindrical fin. The temperature of the fin at the tip and base are 25 °C and 50 °C, respectively. The dia
Mrrafil [7]

Answer:

The fin temperature in °C at a distance of 10 cm from the base = 33.78°C

Explanation:

The following assumptions will be made to solve this problem

- The heat transfer coefficient does not change with the time or distance.

- The temperature of the fins varies just in only one direction.

The temperature of the fin at x = 10 cm = 0.10 m from the base can be calculated from the temperature variation with distance formula for a very long fin.

(T - T∞) = (T₀ - T∞)e⁻ᵐˣ

T = T(x) = temperature at any point along the fin

T∞ = temperature at the tip of the fin = ambient temperature = 25°C

T₀ = temperature at the base of thw fin = 50°C

x = any distance along the length of the fin from the base of the fin = 0.1 m

m = √(hP/KA)

h = Heat transfer coefficient = 123 W/m².K

P = perimeter in contact with the base = πD = π × 0.03 = 0.0943 m

K = thermal conductivity = 150 W/m.K

A = surface area in contact with the base = πD²/4 = π(0.03)²/4 = 0.0007071 m²

m = √(123 × 0.0943)/(150 × 0.0007071)

m = 10.46

mx = 10.46 × 0.1 = 1.046

(T - 25) = (50 - 25) e⁻¹•⁰⁴⁶

T = 25 + 25 e⁻¹•⁰⁴⁶ = 25 + 8.78 = 33.78°C

8 0
3 years ago
How do Solar Engineers Help Humans?<br> (2 or more sentences please)
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Solar engineers work in any number of areas of engineering products that help harness energy from the sun. They may research, design, and develop new products, or they may work in testing, production, or maintenance. They may collect and manage data to help design solar systems.
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To water his lawn, a homeowner uses two hoses. One connects to the faucet, the other to the end of the first hose to make the ho
Shtirlitz [24]

Answer: to be exact you need 28mm of tubing for that

Explanation:

When the election

8 0
4 years ago
Hot water at an average temperature of 88°C and an average velocity of 0.4 m/s is flowing through a 5-m section of a thin-walled
SIZIF [17.4K]

Answer:

a) The rate of heat transfer will be 19.58 Watts.

b) The temperature drop of the hot water will be 0.024 Degree Celcius.

Explanation:

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3 years ago
An excavation is at risk for cave-in and water accumulation because of the excess soil that has accumulated. What type of excava
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Answer:Topographic map. Contour line. Learning Objectives. After completing this chapter, you will be able to: □ Define civil engineering and civil drafting.

Explanation:

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3 years ago
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