It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of 0 o C, for example, the wind-chill temperature is − 5 o C with 20 km/h winds and − 9 o C with 60 km/h winds. That is, a person exposed to 0 o C windy air at 20 km/h will feel as cold as a person exposed to − 5 o C calm air (air motion under 5 km/h). For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 34 o C . and For a convection heat transfer coefficient of 15 W/m 2. K, determine the rate of heat loss from this man by convection in still air at 20 o C . and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m 2. K as a result of winds? What is the wind-chill temperature in this case?
It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of 0 o C, for example, the wind-chill temperature is − 5 o C with 20 km/h winds and − 9 o C with 60 km/h winds. That is, a person exposed to 0 o C windy air at 20 km/h will feel as cold as a person exposed to − 5 o C calm air (air motion under 5 km/h). For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 34 o C . and For a convection heat transfer coefficient of 15 W/m 2. K, determine the rate of heat loss from this man by convection in still air at 20 o C . and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m 2. K as a result of winds? What is the wind-chill temperature in this case?
It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of
0
o
C,
for example, the wind-chill temperature is
−
5
o
C
with 20 km/h winds and
−
9
o
C
with 60 km/h winds. That is, a person exposed to
0
o
C
windy air at 20 km/h will feel as cold as a person exposed to
−
5
o
C
calm air (air motion under 5 km/h).
For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of
34
o
C
.
and For a convection heat transfer coefficient of 15 W/m2. K, determine the rate of heat loss from this man by convection in still air at
20
o
C
.
and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m2. K as a result of winds? What is the wind-chill temperature in this case?
2. A flat belt drive consists of two 4-ft diameter cast-iron pulleys spaced 16 ft apart.
A power of 60 hp is transmitted by a pulley whose speed is 380 rev/min. Use a
service factor (Ks) pf 1.1 and a design factor 1.0. The width of the polyamide A-3
belt is 6 in. Use CD=1. Answer the following questions.
(1) What is the total length of the belt according to the given geometry?
(2) Find the centrifugal force (Fc) applied to the belt.
(3) What is the transmitted torque through the pulley system given 60hp?
(4) Using the allowable tension, find the force (F₁) on the tight side. What is the
tension at the loose side (F2) and the initial tension (F.)?
(5) Using the forces, estimate the developed friction coefficient (f)
(6) Based on the forces and the given rotational speed, rate the pulley set. In other
words, what is the horse power that can be transmitted by the pulley system?
(7) To reduce the applied tension on the tight side, the friction coefficient is
increased to 0.75. Find out the…
The tooth numbers for the gear train illustrated are N₂ = 24, N3 = 18, №4 = 30, №6 = 36, and
N₁ = 54. Gear 7 is fixed. If shaft b is turned through 5 revolutions, how many turns will shaft a make?
a
5
[6]
b
CE-112 please solve this problem step by step and give me the correct answer
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